Revit Training- Create coordinated, consistent and comprehensive model-based designs

Create coordinated, consistent and comprehensive model-based designs

Use Revit Training BIM (Building Information Modeling) software to improve efficiency and accuracy throughout the project lifecycle, from concept phase through visualization and analysis, to manufacturing and construction.

Revit training courses
Revit training courses

Start 3D modelling with remarkable precision

Automatically update floor plans, elevations, and sections as your model grows.

Let Revit handle repetitive routine tasks through automation, so you can better focus on higher-value tasks.

Collaborate with multiple teams, disciplines and time zones

Revit is BIM software that allows all disciplines of architecture, engineering and construction to be integrated into a unified modelling environment, for more efficient and profitable projects.

Project teams can work together anytime, anywhere with Revit using BIM Collaborate Pro, a powerful and secure cloud-based collaboration and data management solution

Extend BIM workflows and save them with Revit in a collection

The Architecture, Engineering and Construction Collection solution provides designers, engineers and contractors with CAD and BIM tools that support projects from the studio to the Jobsite.

In addition to Revit, the collection includes the following components:

  • AutoCAD
  • Civil 3D
  • Navisworks
  • InfraWorks
  • ReCap Pro

Architectural design

What you can do with Revit?

Design and documentation

Place smart items like walls, doors, and windows. Revit generates floor plans, elevations, sections, schedules, 3D views, and renderings.


Generate photorealistic renderings. Create your documentation with bounded and 3D views, as well as stereo panoramas to convert your design into virtual reality.

To analyse

Optimize building performance during preliminary design, make cost estimates, and monitor performance throughout the life of the project and building.

Multidisciplinary coordination

Since Revit is a multidisciplinary BIM platform, it allows you to share model data with engineers and contractors, thereby reducing coordination tasks.

Introduction to the Solar System and its Components


The solar radiation that reaches the Earth in a year represents more than 10,000 times the world’s energy consumption of all forms and combined uses and our benefactor star has a predictable lifespan of 5 billion years.

More Over

Fossil (coal, oil and gas) and fissile energy deposits (uranium), even the most extreme, represent only a few dozen years at the rate of their current consumption (one little more than a century for coal), and since this consumption does not cease to increase, in particular with the thirst for “savings emerging ”from the most populous countries on the planet (China, India, Brazil) to imitate our own behaviours, the end of their exhaustion does not stop getting closer.

 Solar system installation
Solar system installation

Photovoltaic Effect

The photovoltaic effect, discovered in 1839 by the French Antoine-César Becquerel, designates the capacity that certain materials have, especially semiconductors, to directly convert the different components of sunlight (not heat) into electricity.
The photovoltaic effect thus represents the only existing alternative to
production of electricity from the mechanical force, since all other techniques without exception, renewable or not, make use of rotating generators (alternators or dynamos) which can be operated in various ways: steam, wind, the force of water, current sailors …


In addition to this specificity which clearly distinguishes it from others technical, photovoltaics has many qualities that have as many advantages:
Based on an imperceptible physical phenomenon
its functioning causes absolutely no nuisance or impact on the environment
no movement, no noise, no smell, no emission whatsoever.
The operation of a photovoltaic system does not require any moving part, the risk of breakdown or accident is therefore almost zero and the level of reliability very high.
The physical characteristics of photovoltaic materials do not deteriorate over time, and the performance of the panel’s decreases, that we can possibly observe and mainly due to minor manufacturing imperfections, is very slow and very limited, this which allows manufacturers to provide a guarantee of performance that can go up to 30 years old.
Apart from the investment cost, access to energy resources primary is completely free and free, since it is the light of the sun, and since the maintenance and servicing needs are very reduced (they mainly concern the electronic regulation and connection), the economic outcome is predictable with a high degree of certainty.
The amount of energy recoverable in a given location is directly proportional to the area exposed to sunlight, which gives photovoltaics an intrinsically modular and flexible character: the surface area of ​​the sensors ranges from a few cm2 to supply a calculator to several hundred thousand m2 for ground-based plants and this size can be changed at any time by simple addition (or withdrawal) of “slices”, without even interrupting the operation of the existing installation.
Free, harmless, accessibility, security, reliability, modularity, flexibility: the combination of these qualities available to photovoltaics means that its fields of application are extremely diverse and can meet a wide variety of needs in all kinds of situations, especially more than the different manufacturing technologies of the modules which are available today and will be tomorrow thanks to the many axes industry research to adapt the photovoltaic system the characteristics of the place and the intended use of the energy produced.

Sites Isolation

Certain sites, dwellings or others, are not or cannot be connected to the public distribution network because it is technically too complex to extend the network to them (in mountainous areas by example) or because the cost of such an operation is not justified by compared to other existing solutions. These sites are called "sites isolated ”.

Solar Voltaic Energy

However, it is often essential to have access to electricity in order to provide some basic services such as lighting, production of cold, or the power of radio. These sites may then be supplied with electricity by solar photovoltaic energy.
Photovoltaic solar makes it possible to bring electricity to an isolated site, there where it is expensive to produce.

The components of a solar system


The module includes several photovoltaic cells assembled together to each other thanks to an electrical circuit, the photovoltaic module is the central element of a photovoltaic Solar system. To avoid damage caused by the return of current to the module, a bypass diode is installed on each diode. The dimension of the modules photovoltaics varies from manufacturer to manufacturer.


The function of the inverter is to transform the direct current coming from AC panels. Using an inverter is not essential for isolated sites.


Converters make it possible to adapt the power generated in order to make it useful. We have two types of converters for a panel solar: DC / DC and DC / AC. The former provide a DC voltage different from the incoming one and the others make it possible to obtain a AC voltage.


The role of the battery is to store energy for use when the panels don’t create energy at night. The
Solar batteries are essential on an isolated site. The batteries are charged during daylight periods in order to be able to supply the site night or days with very bad weather.


The regulator allows regulating the energy coming from the panels until the battery stops charging the battery when it is fully charged in order to avoid overcharging the battery and discharge, by controlling the outgoing energy. The regulator prevents the battery from ageing prematurely and optimizes charging and discharging.
Most consumer electrical appliances operate on alternating currents. These devices will require an inverter that will transform the direct current, produced by panels, in alternating current.


Electricity produced in direct current by solar panels

(1) is stored in lead-acid batteries
(2) A solar regulator
(3) protects batteries from too deep discharges and overloads.
(4) Electricity is consumed in the receivers

as needed of the user:
direct current (12V, 24V) directly from the battery, for small systems
in alternating current 230V, via an inverter, for solar system fatter Autonomous solar system are very easy to use, they do not require almost any maintenance compared to a group generator. They are also completely silent and do not generate pollution (exhaust gas, used oil, CO2).
It costs less than an extension of the Sénélec electrical network (if there is more than one km to cover), and once purchased, there is no more bill to pay!


An autonomous solar system is sized according to the needs user's electrical system. In the case of solar photovoltaic, the battery undergoes most of the time one cycle per day, that is, it is recharged during the day and then discharged in the evening. The depth of battery discharge at each cycle directly influences its battery life.

The deeper the discharge, the shorter the battery life.


The price of panels has been falling steadily since 2008 and has reached very low levels today. Inverters and regulators, such as many electronic devices, see their prices drop little by little.
Only batteries remain expensive, and their price is not close to going down because of the lead speculation and the demand generated by electric automobiles.
This makes off-site solar systems more and more accessible, but not within the reach of all budgets because of the batteries.

What is a short circuit?

In electricity, the notion of short-circuit comes up very often. Usually associated with danger, shorting is something you want to avoid. But by the way, do you know what a short circuit is? What happens from an electrical point of view during a short circuit? Find out the answers to these questions in our short circuit guide.

short circuits
short circuits

The definition of a short circuit

Principle of short circuit
In electricity, a basic circuit is represented by a generator (battery, battery, etc.) which supplies current to devices (dipoles) such as a lamp, a capacitor etc. When the circuit is closed, the current leaves from its source and passes through the equipment before returning to the generator.
In the event of a short circuit, the current takes a shortcut. Instead of passing through the circuit equipment, it returns directly to its source. In other words, the current becomes trapped in a loop that causes the intensity to increase and heat up. A short circuit can be accidentally caused when a connecting wire strikes its insulating plastic sheath. It can also be caused by inserting a jumper wire between the terminals of the generator or dipole.
An example of an electrical short circuit
Take the example of an electrical circuit comprising a generator and three bulbs connected in series. In normal times, the current leaves the generator and successively feeds the three bulbs. If one of the bulbs is short-circuited, the current will no longer flow through this dipole. As a result, the current will only feed two lamps. Concretely, this means that the short-circuited lamp will not light up. On the other hand, because of the short circuit, the other two lamps will shine brighter and run the risk of burning out. To learn more details about short circuits click here

The different types of short circuits

There are different types of short circuits. They can be classified according to different parameters. For example, considering the duration, we will speak of a self-extinguishing, fugitive, semi-permanent or permanent short-circuit.
The cause of the short circuit can also vary. In the event of a broken conductor, we will speak of a mechanical short-circuit. This is the case, for example, if you forget a tool that connects the terminals of your car battery. The short circuit can also come from an electrical surge after a lightning strike, for example. Finally, humidity, ageing or degradation of the insulation can also be responsible for a short circuit.
Finally, the nature of the connection makes it possible to qualify a short-circuit. For example, a short-circuit is said to be “free” during direct contact between the two terminals, unlike a so-called “impedance” short-circuit. For a three-phase network, short circuits can be:
Single-phase in the case of one phase with neutral;
Biphase for two phases;
Three-phase for three phases;
Two-phase-earth when two phases are connected with the earth.

The short circuit from the point of view of theory

Another way to understand what a short circuit is is to go back to the fundamentals of electricity from a formula point of view.
Ohm’s law in direct current dictates that the voltage (U) is equal to the product of the resistance (R) and the current (I): U = R * I. The resistance reflects the property of a component to oppose the passage of a current. For example, a bulb has a certain resistance. During a short circuit, the component is bypassed by the current. Nothing (or almost) then opposes the flow of current and the resistance of the circuit tends to zero. Therefore, the intensity increases towards infinity.
The increased intensity causes heat dissipation via the Joule effect. This conforms to the following formula: P = R * I², where P represents the power dissipated by the Joule effect.
In short, a short circuit causes the current to rise sharply, causing the circuit to heat up. This is why short circuit phenomena must be able to be detected early and corrected. Otherwise, you risk damaging your circuit. Adding heat can cause the insulation covering your equipment to melt and burn out. On a larger scale, the short circuit can be responsible for household fires.

How to protect your electrical installation against short circuits?

Considering the dangers of a short circuit, there are different pieces of equipment to protect the electrical installation of a home.

The electric circuit breaker

The circuit breaker is an electromagnetic device that automatically cuts off the current when a short circuit is identified. The circuit breaker can be thermal or differential. Once the problem has been eliminated, the circuit breaker can be reset.
Circuit breakers are widely used in a home. This is how you have a branch circuit breaker installed next to the GFCI on a row in your electrical panel. The role of this circuit breaker is to protect a given circuit against short circuits or overloads. A subscriber circuit breaker is also installed upstream of your electrical panel in the technical shaft of the accommodation. Its role is to provide the interface between the general electrical network and your personal installation. Only the electricity supplier is authorized to operate this circuit breaker.

The basics of electricity

Installation, replacement of electrical circuit breaker
The electric fuse
The electric fuse works on the same principle as a circuit breaker. In the event of a short circuit or an electrical overload, it automatically cuts off the power. The main difference with a circuit breaker is that the fuse cannot be reset. It must therefore be replaced after each use. A fuse is in fact made up of a piece of metal (lead for old fuses) that melts during a short circuit or overload. Once the filament is melted, electricity cannot pass through. Compared to circuit breakers, fuses are cheaper and allow circuit overloads to be detected more quickly.


Grounding outlets, equipment and the circuit is also a means of protection against short circuits. Earthing concretely consists in creating a physical connection with the ground. In the event of a short circuit, the current is therefore automatically diverted to the ground.

What is the difference between a lithium battery and an alkaline one?

Today, in the electric battery market, there are different types of batteries that meet various needs. Indeed, there are saline batteries, alkaline batteries and lithium batteries. Here we are going to take a look at lithium batteries and alkaline batteries to understand what makes them different and what are the advantages of each of these battery technologies.

Duracell batteries

What is an alkaline battery?

Alkine battries
Alkaline batteries

Let us briefly recall how an electric battery works. A battery is made up of an anode (positive pole of the battery) and a cathode (negative pole of the battery), both immersed in an electrolyte (conductive substance). The chemical reaction creates a source of energy to power electrical or electronic devices.

In everyday life, the alkaline battery replaced the saline battery, a little less elaborate battery. In an alkaline battery, the anode is made of zinc and the cathode is made of manganese dioxide. The anode and cathode are immersed in an alkaline electrolyte, hence the more common name of an alkaline battery.

Alkaline batteries are used for remote controls, flashes, flashlights, clocks, etc. For devices with medium energy consumption, alkaline technology is the most suitable.

The most popular types of alkaline batteries are batteries, AAA batteries, C batteries, D batteries, etc. Their voltage ranges from 1.5V to 9V.

What is a lithium battery?

 alkaline battery
alkaline battery

In a lithium battery, the anode is made of lithium or a compound of lithium. Depending on the types of lithium batteries, their voltage varies from 1.5V to 3.6V. For the general public, the main chemical process used is lithium manganese (Li-MnO2). The anode is therefore made of lithium and the cathode of manganese dioxide. They are used for energy-intensive household appliances such as certain types of remote controls, computers, cameras, calculators, smoke detectors, alarm systems, etc. Other types of lithium batteries are used extensively in industry as well. The types of lithium batteries, which are sold to the general public, are C button batteries (CR2016, CR2025, CR2032, etc.), batteries for watches, SAFT Lithium batteries, etc.

The difference between a lithium battery and an alkaline

We have just explained what an alkaline battery and a lithium battery are. We will now detail the difference between a lithium battery and an alkaline one.

Rechargeable or not?

The alkaline battery, like the lithium battery, is not rechargeable. These are primary batteries. This means that it offers single-use.


Lithium batteries have a longer life than alkaline batteries. Indeed, they last up to 7 times longer than conventional alkaline. Lithium batteries are perfect for devices that require a long battery life so that they cannot be changed too often. Alkaline batteries are more suitable for everyday devices.

Battery weight

Pound for weight, lithium batteries deliver more power than alkaline batteries and last much longer. Lithium batteries are lighter and more compact than alkaline batteries.

Temperature resistance

The lithium battery is more resistant to extreme temperatures. Indeed, the lithium battery can be used at temperatures ranging from -40 ° C to + 60 ° C. You can therefore use it in very cold/hot weather. The alkaline battery, for its part, cannot be used above -10 °.

Battery price

Alkaline batteries are cheaper than lithium batteries. Lithium being a rarer metal, the price of the lithium battery is, therefore, more expensive than the alkaline battery.

Voltage relay: purpose, the principle of operation, device, types

Voltage relay: purpose, the principle of operation, device

Electrical engineering of our day is sensitive to mains voltage surges, so the lack of a fight against them can entail serious consequences for it. And, we will note, attracts all the time. Network providers are slow to upgrade their mossy power lines, substations and transformers, and the quality of the current in the networks is deteriorating every day. If industrial structures – where do they go? – are fighting this scourge by installing protective equipment at the entrance to their enterprises, then the “people’s” networks are often ownerless, and what kind of current jumps in them – in fact, no one knows. That is why, since there is little concern for citizens nowadays, they themselves should take care of themselves, protecting their personal power grids by means of a device called a voltage control relay, or simply a voltage relay. This is a device that will exclude the very possibility of overloads, and thus the breakdowns to which they lead.

What is a voltage monitoring relay? What is its purpose? How does a voltage relay work? What are the principles of its operation, structure and types? We will now give an answer to these questions, which always arise before those who are confronted by the situation with the need to purchase this device.

Voltage relay
Voltage relay

What the voltage relay protects from. Causes of network surges

There are various reasons for power surges. One of them is a break in a power line (for example, due to strong wind), the consequence of which is a real current shock to the equipment, leading to its burnout if it is not protected. Damage to the neutral wire can have the same consequences.

Another cause of power surges is the location of the transformer. With its location too far from the building, the level of current transmission may one-day “collapse”, and, clearly, this does not bode well for your technology.

The inclusion of a powerful device with a high level of energy consumption can also lead to voltage surges in the network. At the moment when this happens, the current in the second phase drops sharply. Devices that are in the first phase may become unusable or simply burn out from this.

All these problems are a real scourge of the power grid, and only a voltage relay can insure you against them.

Why and why do you need a voltage relay? What does a voltage relay do? What is the very principle of operation of a voltage relay? We will discuss this in detail below.

The principle of operation and the device of the voltage relay

The operation of the relay is ensured by the combined action of its two parts – electronic and power. The first monitors the voltage in the network and controls it, and the second, based on the data of the first, adjusts the load.

The heart of the voltage relay is a microprocessor that controls all of its operations. Its use today is considered necessary, since only thanks to it, the voltage regulation through the relay occurs smoothly.

The main criterion for the operation of the voltage relay is the speed of its operation: in order for the relay to effectively protect the equipment it protects, it must be very high. In modern relays, the response speed is determined by the specified settings and is set based on the conditions of use of the device.

The difference between a voltage relay and a stabilizer

The relay does not equalize the voltage, as the voltage regulator does, but simply de-energizes the load if the current parameters have exceeded the established limits of the rating. Therefore, the effectiveness of the relay is absolute: it is the protection of electrical appliances in its present and strict concept.

Scope of use of the relay

This scope is very wide because the voltage relay is used wherever it is necessary to protect electrical appliances from current overloads. Since electrical engineering is ubiquitous today, the accompanying relay can be placed in any room – of course, in compliance with all electrical safety standards.

The voltage relay protects any network, therefore there are single-phase and three-phase. The reasons for power surges are indifferent to him since it fights against any of them radically – by opening the network. The relay is extremely effective for the protection of devices with a large load on the electric motor, as well as devices with high inertia of operation in the transition to various operating modes. A number of electrical installations need voltage with rigid boundary parameters or full-phase – in this case, a voltage relay is also indispensable. In production, it ensures the uninterrupted operation of industrial equipment, in the life of offices and home life – it protects expensive and sensitive equipment from network surges. Variants of specific devices are determined by the place of their application: industrial relays belong to the class of group relays, the load current of which is high, and the installation is carried out only in the switchboard; individual relays, used in offices and homes of citizens and connected between the load and the outlet, can be installed by yourself, and a shield is not always needed for this.

Benefits of voltage relays

  • The voltage relay has a lot of advantages. Reliably protecting electrical engineering from all sorts of surprises, it, moreover, has the widest range of applicability and in this sense belongs to the category of universal electrical devices. Here’s why it is good:
  • The use of a relay eliminates the cost of repairing electrical equipment due to its breakdown from power surges in the network.
  • The temperature range of its operation is from -20 to + 40 ° С, which means that it can be used not only indoors, but also outdoors – of course, in a sealed cabinet.
  • The device is easy to install and does not need to be invited by a specialist – at least in the case of a socket-type relay.
  • Relay models are aesthetic in appearance and do not violate the harmony of the interiors of the premises by their presence.
  • The market offers tremendous opportunities for choosing the optimal relay option, both in terms of performance and price.
  • How to choose a voltage monitoring relay for home and apartment
  • Buying a voltage relay requires adherence to a number of simple rules. They are as follows:
  • Buy the relay from a specialist store, where you will be given a real warranty on it. Be sure to familiarize yourself with it and read the relay instructions.
  • To save money on buying relays, remember that the cheapest relays are socket-type, more expensive relays are extension ones, and the most expensive ones are DIN-rail-mounted. Our relays are cheaper than foreign ones; in addition, the price varies by brand, feature set and design. Buy a relay taking into account this and your real situation, but do not save too much: the mean pays twice.
  • When planning the purchase of a single-phase relay, accurately calculate its power, taking into account the magnitude of the load it protects. For a three-phase relay, such calculations are superfluous, since they all have the same power.
  • The best choice of a relay is a device with a display that shows the current value of the voltage in the network: the display will allow you to monitor this value not only for the relay but also for you.
  • The material of the relay case must be non-flammable – polycarbonate is best suited for its role.
  • Make sure that the relay has a thermal protection function – this will allow it to perform its tasks optimally.
  • Top voltage relay manufacturers
  • The issue of choosing a voltage relay is determined by a number of factors, of which we single out two: the ability to buy a voltage relay of good quality and at a reasonable price (without going beyond the budget segment) – and just buy the best relay, regardless of the contents of your wallet.

If we are talking about the first option, take a closer look at the rating of budget brands. Relays of the ZUBR and ADECS brands occupy the first positions in it by a large margin from the rest. These products will give you a long service life under normal use. Their cost ranges from 390 to 836 UAH, and the breadth of choice within these price ranges is sufficient for you to choose an option for yourself. As for the rating, not constrained by the budget, in 2020 its top was undividedly taken by the ZUBR brand relays: ZUBR D16, ZUBR D25t and ZUBR D32t.

According to the survey of the STROIMDOM construction portal, the places of the best relays in the 2020 rating were distributed as follows: ZUBR relay – 59.84%, Novatek-Electro relay – 10.66%, DigiTOP voltage relay – 8.20%, Adecs relay – 13.11%, Tessla voltage relay – 1.64%, Abb, Hager, Schneider – 5.74%; the share of the rest is insignificant. In our opinion, this picture is very subjective – in it, for example, the indicator of the domestic brand Tessla is underestimated, the reviews of which are good on the network. But we have no reason to doubt that the ZUBR voltage relay is really the best because everyone is writing about it.

It is released in Donetsk. It has a display that shows the dynamics of changes in the mains voltage in real-time. The error of its readings, measured by a high-precision Fluke 87 multimeter, does not exceed 2 V. The range of rated currents for which it is designed is 25, 32, 40, 50 and 63A; at a current rating of 63A, it can withstand 80 A for 10 minutes. The voltage at the upper limit is set in the range of 220 – 280 V, at

the lower limit – in the range of 120 – 210 V. The guarantee given by the manufacturer for this product is impressive – 5 years. Forum visitors write: in reality, it works much longer.

Types of electrical protection relays or protection relays

What is a protection relay?

A relay is an automatic device that detects an abnormal condition of the electrical circuit and closes its contacts. These contacts, in turn, close and complete the circuit breaker trip coil circuit, thereby causing the circuit breaker to trip to disconnect the faulty part of the electrical circuit from the rest of the undamaged circuit.

Now let’s talk about some terms related to protection relay.

Activation signal detection level:

The value of the activation quantity (voltage or current) is on the threshold above which the relay begins to be actuated.


If the value of the activation amount is increased, the electromagnetic effect of the relay coil is increased, and above a certain level of the actuation amount, the relay moving mechanism just begins to move.

Reset level:

The value of the current or voltage below which a relay opens its contacts and returns to its original position.

Relay operating time:

Immediately after exceeding the activate quantity level, the displacement mechanism (e.g. a spinning disc) of the relay begins to move and finally closes the relay contacts at the end of its travel. The time that elapses from the time the actuated quantity exceeds the removal value to the time the relay contacts close.

Relay reset time:

The time that elapses between when the actuation amount becomes less than the preset value and when the relay contacts return to their normal position.

Relay range:

A distance relay operates whenever the distance seen by the relay is less than the pre-specified impedance. The control impedance in the relay is a function of the distance in a distance protection relay. This impedance or the corresponding distance is called the relay reach.

Power system protection relays can be classified into different types of relays.


Relay types

protection relay
protection relay

The types of protection relays are mainly based on their characteristics, logic, actuation parameters and operating mechanism.

Based on the working mechanism, the protection relay can be classified as an electromagnetic relay, solid-state relay and mechanical relay. In reality, a relay is nothing more than a combination of one or more open or closed contacts. All or some specific relay contacts change state when activation parameters are applied to the relay. This means that open contacts become closed and closed contacts become open. In an electromagnetic relay, these closings and openings are made by the electromagnetic action of a solenoid.

In the mechanical relay, the closing and opening of the relay contacts are done by mechanically moving different gear level systems.

In the solid-state relay, it is mainly carried out by semiconductor switches such as the thyristor. In the digital relay, the activated and deactivated state can be called state 1 or 0.

Based on the characteristic, the protection relay can be classified as

Definite time relay

Inverse time relay with defined minimum time (IDMT)

Instantaneous relays.

IDMT with inst.

Characteristic in steps.

Programmed switches.

Voltage limitation on the current relay.

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Based on the logic, the protection relay can be classified as follows:



Neutral displacement.


Restricted earth fault.

On fondant.

Distance diagrams.

Bus bar protection.

Reversed power relays.

Loss of excitement.

Negative phase sequence relay, etc.

Based on the activation parameter, the protection relay can be classified as

Current relay.

Voltage relay.

Frequency relay.

Power relay etc.

Depending on the application, the protection relay can be classified as follows:

Primary relay.

Emergency relay.

The primary relay or primary protection relay is the first line of protection of the power system, while the backup relay is only used when the main relay does not operate in the event of a failure. Therefore, the backup relay is slower in action than the main relay. Any relay may not be used for one of the following reasons:

The protection relay itself is defective.

The DC voltage supply to the relay is not available.

The tripwire from the relay panel to the circuit breaker is disconnected.

The trip coil in the circuit breaker is disconnected or defective.

Current or voltage signals from CT or PT respectively are not available.

Since the backup relay only operates when the main relay fails, the backup protection relay should not have a point in common with the primary protection relay.

Some examples of mechanical relays are-


OT  (travel oil temperature)

WT trip (winding temperature trip)

Bearing temp travel etc.

Float type




Water level controls etc.

Pressure switches.

Mechanical locking

Pole mismatch relay.

List Different protection relays are used to protect equipment from different power systems

choosing a career as an electrical engineer.

Electrical appliances are proving day by day essential for our daily lives. In the modern world, electronic gadgets penetrate into every aspect of our lives (at home, in the office, at school, etc.) and make our daily tasks simple and easy. From clever inventions such as the microwave, the calculator and the clock, to computers and spaceships.
Electronic gadgets are inextricably linked to our modern way of life. Only calculate the number of employees who could not work if the computers stopped working. A typical example is a mobile phone, which is an integral part of our daily lives. But who are the professionals behind these inventions? Below you can read more about the position of an electrical engineer.

Electrical Engineering
Electrical Engineering

The object of work of the electrical engineer.

Electrical engineers use the principles of mathematics and physics to design, develop, and evaluate electrical and electronic equipment and systems. They work with a range of technologies, including home appliances, lighting and electrical systems, telecommunications, and satellite systems. As in any profession, here too there is specialization in the fields of electronics, microelectronics, energy, telecommunications, etc.

Career options for an electrical engineer.

Electrical engineers use the principles of mathematics and physics to design, develop, and evaluate electrical and electronic equipment and systems. They work with a range of technologies, including home appliances, lighting and electrical systems, telecommunications, and satellite systems. As in any profession, here too there is specialization in the fields of electronics, microelectronics, energy, telecommunications, etc.
Career options for an electrical engineer.
The field of electromechanics is huge and given the generalized nature of electronics, there are many areas of specialization to choose from, as mentioned above. Among the different options are electricity, lighting, electrical measurements, control, signal processing, automation, machine installation, biomedical technology, nuclear power, microelectronics in the public or private sector. Also, the number of responsibilities is wide: the study of the feasibility of a new project, design of new systems but also their maintenance, participation in fault diagnosis, data analysis, and much more.
Depending on the requirements of the job you are looking for, there is a choice of fast pace or a focus on research and development. More specifically, the consumer electronics industry is changing rapidly and is highly competitive. Companies have to launch new products every six months. On the other hand, in the field of medicine or in the field of defense systems, security is the most important factor and in this part long-term product development cycles are required, which emerge as a result of thorough research. It is worth noting that opportunities for professional development are offered in abundance: there is a possibility to develop as a chief technical consultant or as an independent contractor.
In addition, as a candidate who wants to work as an electrical engineer, it is good to know that the profession aims to improve systems, with the ultimate goal of improving living standards. Smartphones, for example, have revolutionized communication, electronic systems in medical equipment have made it possible to monitor patient’s progress more effectively, and, finally, electronic systems in the field of defense have ensured the integrity of the states that treat them.
A degree in electrical engineering opens up a variety of professional paths. Given the rapid development of the technology sector, graduates have the opportunity to work in any country they wish and choose a career in various fields, such as industry, information technology, or sales.

The profession of sales engineer.

A different career choice of an electrical engineer is the sale of scientific and technological products or services. To achieve the highest degree of efficiency, a sales engineer must have extensive knowledge of product functions and a full understanding of their effectiveness. Below you can read what is good to know if you choose to look for a job as a sales engineer.
Sales engineers usually prepare and give technical quotes, which explain the products or services offered. Advise customers and engineers, assess needs, and understand customer requirements. They help customers solve problems during the installation of new equipment. They suggest improved materials or machinery, indicating how the changes will reduce costs or increase production. Finally, they help in the research and search of new products.
Many of the sales mechanics’ tasks are similar to those of other salespeople. They need to stimulate the customer’s interest in buying their products or services, negotiating a price, and completing the sale. To do this, sales engineers provide technical – specialized presentations that explain the technical aspects of the product and how that product will solve a specific customer problem. Some sales engineers work with salespeople who focus on marketing and selling the product, which allows the sales engineer to focus on the technical aspects of the job.
Sales engineers should combine their scientific-technical training with their entrepreneurship. This means that they need to be ambitious, extroverted, enthusiastic and of course optimistic.
Are you interested in finding a job as an Engineer? Start your search by clicking here.

10 Short Electrical courses with certificates in 2021

Electricity is one of the basic needs of the world today. Every society relies heavily on electrical power and power supply facilities to live and manage its operations.

Without a proper power source, you can’t use a phone or run a computer, which is why there is a massive demand for electrical engineers and technicians in businesses and industries.

Would you like to work in the electrical technology sector? Do you want to learn about power generation systems? If your answer is yes, you can make your dream come true by taking free online electricity courses.

These courses will give you the practical skills and knowledge you need to build a solid foundation in any electrical career.

Plus, an online electrical technology certification will prepare you to thrive in today’s global world, which needs more highly skilled professionals than ever before.

We will connect you with the best online electricity course options that will help you fit into the wide range of exciting opportunities in this field. To view the details of these programs, please carefully follow the content described below and select the option that best suits your needs.

About the electrical profession

An electrical engineer or technologist is a person who is skilled in the design and development of electrical systems, has the ability to identify and solve electrical and electronic problems.

These professionals test and supervise the manufacture of electrical equipment, such as Circuit Breakers, Transformers, electric motors, electrical panels, and radar and navigation systems.

Why short Electricity Courses?

Electrical technology is not limited to studying science and mathematics. It also covers areas such as economics, business, ethics, and communication. However, there are numerous benefits associated with the discipline of electrical engineering. Some of these benefits include;

Online electrical courses will help you adapt to new tasks and processes quickly.

 This career path will expose you to major projects and industries that will benefit you.

 Electrical discipline helps build one intellectually.

This discipline offers you the opportunity to be a highly innovative potential individual and thus contribute to the growth of technology.

It gives you prestige and financial security.

How do free online electricity courses with certificates work?

Like any other distant program, the online electrical class uses the Learning Management System.

LMS method includes the use of Blackboard, Canvas and Moodle, which provides an accessible exchange of information between you and your instructor.

During online classes, you receive your study materials, lectures, and assignments by email or some kind of file transfer system. Submit course assignments via LMS by posting to discussion forums and submitting assignments via the appropriate links.

Another option for online classes involves the use of an online supervision service.

This helps monitor students as they work. It also allows degree candidates to take off-campus assessments and also gives schools confidence that students honestly earned their grades.

If you exhibit any form of cheating or malpractice, the service can alert the school.

However, the online electricity course offers an introduction to electronic, electrical, and systems engineering. It is an interesting opportunity that will expose you to the following courses;

  • Electrical, Electronic, and Systems Engineering Overview
  • Introduction to systems and systems terminology.
  • Transducers and their purpose
  • Electronic systems in context.
  • Solar / Battery Related Issues in Space
  • Introduction to the space weather research group
  • Electrical circuits
  • The differences between analogue and digital electrical engineering
  • Introduction to digital electronics.
  • Railroad Platform Armor Wall Control Systems Overview

How do I apply for free electrical engineering/electrician courses online?

Choosing to take an online or physical course in electrical technology to learn a new skill, or even just as a refresher on the skills you already have, is a very honourable thing to do.

The first step you need to take is to choose an online electrician course, then you will get a form and complete the registration process. See the list and details of the available programs below.

During the registration process, you will be asked to set up an account that includes certain personal information. Unlike other online courses, an electricity class may not involve you uploading the electronic versions of your documents.

The short electrical courses in Lahore are fully compatible with any type of device and Internet connection. Whether you are using a Windows computer, Mac, smartphone, or tablet, you will get the same experience while learning.

By completing the online registration, you will be granted access to select your grade level and course of study and then you can begin enrolling in any class.

Start by choosing the specialization you would like to start with. When you enrol in a course that is part of the specialization, you are automatically enrolled on BES.

After successfully completing and passing the course, you will be able to earn an Accredited Certificate of Achievement.

What is the duration of the short electrician course?

The length of online classes varies by schools or course providers. However, some schools offer courses that can be completed in as little as five weeks, while others do not have to be completed within a year.

A typical free online electricity course with certificates lasts 12 weeks, some can take up to 14 weeks depending on the type of program.

You must understand that the duration of your online courses depends on your power. For example, most instructors post assignments at the beginning of the program, so if a course is said to be eight to nine weeks long, you can complete the work and submit it as you wish.

What are the best online short electricity courses?

online electricity courses have everything you need to understand electrical systems from start to finish. From the management of critical commercial and industrial equipment to the diagnosis and repair and maintenance of basic electrical circuits.

We have compiled the list of 10 f online programs for interested students. Our selection criteria for these programs focus on the duration and nature of the coursework offered. We also consider the quality of education, average earnings of graduates, accreditation, and several other relevant factors.

As you read more, you will get detailed information on the various programs offered by the free online schools listed below.

Short electrical courses in lahore
Short electrical courses in lahore

 Introduction to Basic Electrical Drawings and Test Equipment – Revised

Battery storage technology: opportunities and uses

Master Track Certificate of Construction Engineering and Management

Introduction to electronics

Energy production, distribution and security

Critical installation – power supply management

Solar Power Basics

Introduction to short electrical courses with wiring systems

Components of electrical transformers

Wind power

# 1. Introduction to Basic Electrical Drawings and Test Equipment – Revised

This specialization tops the list of our Short electrical courses. The reason is that it focuses on the basics of electrical technology.

In this course, you will learn how to accurately interpret electrical drawings and learn the uses of important electrical equipment with this online course, By the end of the course, you will get to know the concept of energy, lighting, and communication, and be much more familiar with important electrical symbols and test equipment.

This course is provided by Alison and she already has 30,952 enrolled, you can request to join them.

Apply Here

You can take your career to the next level by enrolling in one of the best Electrical Engineering schools in the world

# 2. Battery storage technology:

Opportunities and uses

In this course, you will learn about promising battery storage technologies; exploring their functioning, strengths, weaknesses and a possible place in the future. In addition to that, you will explore a variety of uses for battery storage equipment in power, transportation, industry, and more.

The course covers the following topics;

The need for flexibility demand in the EU electricity industry and the role of battery storage.

Battery storage technologies: characteristics, potentials and limitations.

Battery storage network scale application

Battery storage app behind the meter

The off-grid battery storage application

Mobile battery storage app

By the end of the course, you will understand the use of battery storage technology, how it works, the opportunities it presents, and why it is not in high demand today.

Apply Here

BES Certificate of Engineering

This is an advanced online Certification program that will prepare you to become a qualified Construction Manager in 7 months.

This specialization is presented by the University of Michigan; one of the highest-ranked institutions in the country.

The course covers the following topics;

How construction projects are created, organized and financed

The appropriate techniques to properly account for ongoing construction projects.

Best practices for keeping construction projects organized and on time

How to use the right equipment for efficiency and safety.

Leading Sustainability Practices in the Construction Industry Today

At the end of this training, you will gain skills in construction accounting, project scheduling techniques, and more.

Apply Here

# 4. Introduction to Industrial Electrician in Lahore

Georgia Tech offers this specialization through BES. There are already 100,627 registered.

Georgia also offers many research opportunities to students including the ECE Undergraduate Research Opportunities Program (UROP).

In this specialization, you will learn the basic components of electronics: diodes, transistors, and operational amplifiers.

Course work in this specialization covers the following topics;

Concepts of the theory of linear circuits.

The operational amplifier and its applications.

Examination of additional applications of operational amplifiers.

Filter Transfer Function Exam

Develop an understanding of the PN junction diode and its behaviour.

 Develop the ability to analyze diode circuits.

By the end of this course, you will be under basic operation and some common electronic circuit applications.

Apply Here

# 5. Energy production, distribution and security

This specialization features four topics that provide introductory knowledge about the power industry and associated career opportunities to those considering a career in the electrical engineering field.

At the end of this training, you will become familiar with electrical power systems, natural gas, safety practices, and the energy industry as a whole.

# 6. Critical Installation: Power Supply Management

This free online critical installations course focuses on supplying and managing electricity for critical equipment. It is provided by Alison and currently has 2,450 students enrolled.

In this specialization, she will learn about the safe and efficient maintenance and management of power supply systems, power distribution systems, and preventive distribution measures.

Apply Here

# 7. Solar System Installation & Design training courses.

This course is an introduction to the fundamentals of solar energy as applied to solar panel system installations. It provides a good overview of the components and functions of the system but uses some simplified assumptions.

The basics of solar energy are provided by BES. There are already 9,840 enrolled in this course, you can join them by clicking the request button below.

At the end of this course, you will gain an understanding of advanced site assessment coverage, factors affecting efficiency, and the size, design, and integration of photovoltaic systems.

Apply Here

20 Undergraduate Scholarships for Electrical Engineering Students in Developing Countries

# 8. Introduction to electrical supervisor training

This specialization course covers essential electrical wiring systems, including raceways and device boxes.

You will learn about each of the constituent parts of an electrical wiring system, as well as proper handling techniques and installation and storage procedures for different electrical wiring components.

Introduction to Electrical Wiring Systems is a free online electrical course option presented by Alison. There are already 11,973 students enrolled, you can get started by applying below.

Apply Here

# 9. Components of Electrical Supervisor training in Pakistan

This is another speciality course powered by BES. You will learn about the construction and components of electrical transformers. Electrical transformers are an essential component in any electrical distribution system and are vital for the proper transmission of energy through an electrical network.

This online course uses detailed 3D models to teach you about the functions and components of the electrical transformer.

Apply Here

# 10. Wind power

Wind Energy is a free online electrical course with 55,876 already enrolled.

This course will give you an understanding of wind energy and through practical exercises, you will learn to perform wind energy calculations based on simple models.

At the end of this training, you will gain foundational disciplines of wind energy research such as wind measurements and resource assessment, aerodynamics, wind turbine technology, structural mechanics, materials, financial and electrical systems.

Apply Here

What are the benefits of online short electrical courses?

Online education has many benefits, which is why many students consider it more advantageous than learning on campus. Some of these benefits are listed below.

First, online learning gives you time and space to deepen and master a new skill.

As a student, you can earn all-academic degrees online, from a career certificate to a PhD.

Online education is a cheaper option than traditional schools; there are no travel costs, and sometimes required course materials, such as textbooks, are available online at no cost.

Students can take online courses and even complete full degrees while working while doing intermediate jobs; this helps improve career advancement.

See this too 10 good reasons to study electrical engineering

What can I do with a free online electrical certificate?

Electrical technology is one of the science and technology professions that has a variety of job opportunities. With an online electrical certificate, you can find relevant opportunities in a variety of sectors, including GE Aviation, the US Department of Energy, and many others.

How much do electrical engineers earn?

The median annual salary for electrical engineers was $ 96,640 in May 2018 according to the U.S. Bureau of Labor Statistics. The top 10% of all electrical engineers can earn more than $ 143,000 a year and engineers in the 10th Lower% can expect to earn an average of $ 60,000 annually.

According to Pascale, an entry-level electrical engineer with less than 1 year of experience can expect to earn an average total income of $ 2,723.15 based on 5 salaries.

Additionally, an early career electrical engineer with 1-4 years of experience earns an average total compensation of $ 3,981.91 based on 35 salaries. A mid-career electrical engineer with 5-9 years of experience earns an average total income of $ 5,418.72 based on 20 salaries.

Additionally, a seasoned electrical engineer with 10-19 years of experience earns an average total income of # 5596.71 based on 11 salaries.

What is the career outlook for professionals in electrical technology?

Data from the U.S. Bureau of Labor Statistics shows that overall employment of electrical and electronic engineers is projected to grow 2% from 2018 to 2028, slower than the average for all occupations.

As technology advances, more opportunities open in companies and industries for engineers and technicians, so you can make the most of these opportunities by choosing a course that will help you improve your skills.

Frequently Asked Questions for Free Online Electricity Courses with Certificates

How can I register for free online electricity courses?

Follow the next steps;

1. Select the school offering the electrician/electrician online course

2. Complete the online application

3. Interview

4. Start conferences

How long does it take to complete short electrical courses?

Typically, it will take 5-10 months to complete an online electricity course.

Where do electrical engineers work?

Most electrical engineers work in IT companies, manufacturing, communications, and aerospace industries. In addition, they can be used by companies that manufacture navigation controls and medical equipment.


It is possible to obtain complete training in electrical technology online. This training presents a course that covers key concepts taught at the college level.

If you want to get a head start on learning about electricity, enrol today in this online electrical training course and start your career in the electrical industry.

There you will have the opportunity to learn in a way that benefits you.

Installation of solar water heater

Although the installation of a solar water heater is considered a simple task for the plumber, in practice it has been proven that it is not always done properly.
In this short guide, we will not exhaust the topic of installation (base assembly, position selection, etc.) that you will find in all technical installation leaflets of solar, but we will emphasize the points due to which the most frequent failures are due to which You will not find information elsewhere on or off the internet.
Important points that we must pay attention to when installing our solar water heater are:
Installation of pressure reducer in the water supply network
Solar water heaters, like all water heating appliances, are designed and manufactured to operate at maximum operating pressure. (design pressure, rated pressure) If the mains pressure exceeds the rate for a long time, it is very likely that your solar panel will fail. Solar models made in Greece are usually designed for 10bar pressures, while cheap Greek and Chinese solar water heaters are designed for 6bar pressures or in some cases for lower pressures.
The pressure of the water supply network in most areas of our country is 3.5 ~ 4.5 bar, but there are many areas where much higher pressures are observed, especially in areas close to the source of the distribution network. In many areas also, although the pressure most hours of the day is “normal”, there are hours (usually at night) where very high pressures are observed, reaching up to 8bar.
So if our solar panel is designed to operate at 6bar pressures and we install it in an area where higher pressures occur, its lifespan will be significantly reduced.
In such areas, it is important to install a pressure reducer, a device that does not allow the pressure of the water supply network to pass in our house above a limit. It is correct to install the reducer at the entrance of the house and not in the hot water network only, on the one hand, to protect the other elements of the plumbing installation of the house (pipes, valves, coils, etc.) and on the other hand to avoid large pressure differences between cold and hot network.
The setting of the reducer in e.g. 4bar ensures that the pressure at home will never exceed 4bar, no matter what the network pressure.

Solar water heater installation
Solar water heater installation

Install a change filter

In areas with very hard water, it is useful to install a filter at the inlet of the solar to reduce the deposition of waste inside the boiler. The installation of this filter is not always necessary, but in combination with regular maintenance, it will maximize the lifetime of your solar water heater.

Installation of the expansion tank in the closed circuit of the solar.

It is known that when a solid or liquid body heats up, it expands, ie increases the volume it occupies.
It is also known that when we heat a liquid in a container of a certain volume that prevents the liquid from expanding, instead of increasing the volume, the pressure in the container increases.
The closed circuit of the solar (the circuit that includes the solar collector, the connection pipes with the boiler and the boiler exchanger and contains water and anti-coolant), is a closed “container”, with a specific volume, which does not allow the water of the closed-circuit to expand increasing its volume. The increase of the water temperature, therefore, implies the increase of the pressure in the closed circuit.
The reason why a locking valve is placed in the closed circuit is to relieve the pressure when it rises above a limit. But in addition to safety, a small expansion tank (1 liter is enough for solar compacts) should be placed in the closed-circuit at the highest point of the solar panel. The expansion vessel will give the closed-circuit water the required space so that it can expand without increasing the pressure in the closed circuit.
If the solar panel is installed without an expansion tank in the closed circuit, the water will not find space to expand, thus increasing the pressure in the closed circuit. The increase in pressure will cause the safety valve to open to relieve the pressure. When the valve is opened, water will come out of the closed circuit, which means that the closed-circuit will not close, and your solar panel will not work.
If you have a solar panel that frequently forces you to fill the closed circuit with water and antifreeze, check that your solar panel has an expansion tank in the closed circuit and if it does not, add an expansion tank.

Installation of an expansion tank in the open circuit of the solar panel.

Everything we said about the closed circuit, also applies to the open one (the circuit that contains the water of use, the water that ends up in our bathroom). In the open circuit, of course, the taps open, and the pressure is relieved, so one could assume that it is not necessary to install an expansion tank in the open circuit as well.
This thought turns out to be wrong when the water we heat in the solar is not used. If the user of the installation leaves the house for a few days in the summer, the pressure in the open circuit increases (since the taps do not open to relieve the pressure) and this results in our solar (but also the entire hot water network – pipes, valves, connection coils) to be stressed by high pressures and the safety of the solar to be constantly opened.
The same goes for high-performance vacuum heaters with vacuum tubes, which on summer days with maximum sunlight are subjected to very high pressures if the user does not use hot water.
Solar water heater open circuit expansion tank
Therefore, the installation of an open circuit expansion tank is considered necessary to protect our solar water heater and to enjoy hot water without any problems.

Closed-circuit filling.

When installing any solar water heater, the solar panels should remain well covered until the closed and open circuit is filled with water.
If the installer exposes the collectors before filling the circuits, the temperature inside the collectors will rise to very high levels (> 100oC), which will make it very difficult to fill the closed circuit, since the water we will try to put in the closed-circuit will evaporate as soon as it comes in contact with the hot surfaces of the collector. Apart from the fact that it is impossible to calculate the coolant ratio, the filling of the closed-circuit will not be done correctly, due to the evaporation of water.
The filling of the closed-circuit is done with a solution of antifreeze and water in such a ratio, in order to protect our solar from the low temperatures of winter.
The ratio depends on the properties of the antifreeze and is always indicated on the antifreeze bottle. For the solution, it is good to prefer propylene glycol, which is safer for the health of the installer. The filling should be done carefully so that the installer does not breathe vapors of the solution containing antifreeze.
If the antifreeze does not contain dissolution instructions, we can say that for standard antifreeze, a solution of 25% ~ 30% in antifreeze protects our solar at temperatures up to -10oC, a solution of 50% up to -20oC, while for lower temperatures more antifreeze should be used.
The above are general instructions and as we said the proportions in the antifreeze bottle should be observed.
The filling of the closed-circuit must always be done carefully so that no air is trapped in the upper part of the collector or in the boiler-collector connection pipes.

Closed and open circuit piping insulation

The pipes of the open and closed circuit of our solar should be well insulated with armaflex type insulator of the thickness of 9mm and above (we prefer 13mm due to the high temperatures that develop).
All black foam insulators are not resistant to UV sunlight and for this reason, it is very important that the insulation material is protected against sunlight with white or black PVC film, or with a protective paint special to protect the insulation.

After installation

Solar water heaters reach their maximum efficiency 2 days after the completion of the installation. On high-quality models with top solar panels, you can use hot water from day one. In any case, do not rush to judge the performance of your solar panel before 2 days have elapsed.
Common causes for your solar panel not working properly
If the period of 2 days has passed and your solar panel does not heat water properly, then the installer should check that there is not one or more of the following causes for which a solar panel does not work properly.

  • Poor choice of orientation
  • The poor slope of the solar panel
  • Shading of collectors from trees or other tall objects
  • Poor filling of the closed-circuit
  • Leakage in the closed-circuit piping.
  • Incorrect connection of cold / hot piping after solar.

By following the above guidelines and provided you have purchased a high-quality solar water heater, you can be sure that you will enjoy plenty of free hot water for many years and you will definitely recoup the money of your investment.

VFD variable frequency units

VFD variable frequency units

To examine how to control the speed of an engine with a VFD driver (Variable Frequency Driver) we must first remember some basic terms. As we know, single-phase motors and three-phase motors operate according to the principle of operation of induction. They consist of a rotor and a stator without physical contact between the rotor and the stator. According to this principle as we see in the figure below when a frame is found in a changing magnetic field an inductive voltage will appear at the ends.

The motors have a constant speed determined by the supply frequency and the constant torque. The motor impeller rotates at speed n which depends essentially on the axle load. The ratio of the difference between the synchronous speed ns and the motor speed n to the synchronous speed is called the slip s and is given by the formula and the slip is not constant but changes with the load and increases with it.

n = Rotor speed, ns = Stator speed, s = slip.

The speed of the Rotor is given by the formula: Speed ​​therefore for pole pairs it is standard and constant and for a network frequency of 50 Hz is given by the following table:

2 3000

4 1500

6 1000

8 750

10 600

Obviously, a constant speed motor is not suitable for all applications, resulting in the need to adjust the speed as needed. Industrial machinery is often driven by electric motors with speed control devices. These motors are simply larger, more powerful than those driven by home appliances, such as food mixers or electric drills that normally run at a constant speed.

Although many different induction motor speed control techniques have been developed, the most popular control technique is to produce a variable supply voltage that has a constant voltage to frequency ratio. This technique is widely known as V / F control.

A very important observation here is why I change the voltage at the same time I change the frequency and I keep this reason constant what do I want to avoid something very important? Couldn’t I just change the frequency and adjust the speed?



As it is known, the frequency affects the impedance of a circuit since it enters the type of inductive resistance XL = ωL = 2πfL therefore if I reduce the frequency too much to values ​​close to zero the reactive currents according to the law of Ωhm I = V / XL will take too much very high value with the result that I destroy the windings, the motor and the driving circuit, but if at the same time I reduce the voltage then I keep the idle currents constant and at low values.

Therefore V / F = constant.

Variable frequency drive systems.

Variable Speed ​​Drives (VSD or Variable Frequency Drives – VFD) are used to control and adjust the rotational speed of a machine at will.

Typical A typical VFD system consists of three parts: the electric motor (electric motor)

the power converter (inverter), the control system.

Let’s look at the parts of a VFD Inverter one by one.

VFD Parts

We will cover the parts and operation of (VFD) Variable Frequency

Drive. It is important to keep in mind that Drive is only one part of it

systemic. As you will see in the attached photos, we have the disconnect switch, the fuses, the bypass switch, the protection against thermal overload, the BAS, etc., which play an important role in the construction and proper operation of a VFD.

Inside the VFD there are 4 large sections: rectifier, DC link in the middle, inverter and control/adjustment. This fourth section controls

and setting, interfaces with the other 3 sections.

Generally, the operation is as follows. The three-phase or single-phase mains voltage begins to enter the rectifier, where it respectively rectifies it to DC voltage with some ripple. The intermediate circuits normalize and hold the DC voltage at constant levels and connect to the inverter. The latter, the inverter, uses DC voltage to propel the motor at the voltage and current levels depending on the control circuit. The configuration of the pulses going to the motor makes it look like a sine waveform.

Each of these sections is discussed in detail below:

Bypass switch and fuses for a 600Hp Inverter (450KW), in smaller Inverters these two parts are integrated inside the drive.

Converts alternating to continuous.

Thyristors (D1 to D6) allow current to flow only in one direction when their gate signal is activated. In this diagram, the AC power at L1 goes to thyristors D1 and D2. Due to the location of these thyristors, the current can only go up. Thyristor D1 leads when AC is positive and D2 leads when AC is negative. This leads the upper line (+) to a positive potential and the lower line (-) to negative. Thyristors D3 and D4 convert the power of L2 to DC and thyristors D5 and D6 convert L3. A voltmeter can be used to measure this DC voltage. In this type of circuit, the DC voltage is 1.35 times higher than the AC line voltage. Therefore if:

Vac = 240 V, then a voltage of 324 Vdc is produced.

Vac = 380 V, then a voltage of 513 Vdc is produced.

Vac = 400 V, then a voltage of 540 Vdc is produced.

Vac = 575 V, then a voltage of 776 Vdc is produced.

Because in one application the load power and mains voltage can change then the dc voltage will move between the values.

The rectifier section includes the power inlet, thyristors and heat sinks.

See the image below.

On large VDF drives> 22kW = 30 Hp a soft charge circuit is added which helps to charge the dc Capacitors before applying the supply voltage to the rectifier. As you will see in the image below this card is in the upper left corner just above the rectifier and its fuses are on the right. In drivers larger than 350 Hp, IGBT is used instead of resistors to limit the current flowing to the capacitors.

We see a Soft Charge for a 600Hp drive (450kW).      

We see for a Drive 200 Hp the 2 big power protection fuses that go to the capacitors in the DC Link section

Using a series of capacitors and DC reactors the DC voltage becomes more stable.

The blue or black capacitors we can find the store a lot of energy. In the photo, we see three rows of 12 capacitors so a total of 36 capacitors.

There are 2 series of coils as shown above. DC Link coils are always with 2 terminals, shown here on the left. Coils are DC, also known as DC Chokes.

When drivers are asked to have a dynamic brake, the drive comes with an IGBTs brake. When the voltage reaches a very high value in the DC bus, the IGBT brake is activated and sends power to

brake resistance. This is not an option for HVACs.

This brake option, also known as dynamic braking, is used in devices that need to be stopped or changed quickly, such as conveyors, lifts and centrifuges. In brake units, the IGBT transistor is used to remove the extra power that returns to the unit when the engine, which is at high standstill, stops or changes direction. The only HVAC application that can use dynamic braking is for boiler burner fans.

Inverters receive the voltage from the DC bus and use the pulse amplitude (PWM) modulation to send the signal displayed on the motor as an AC signal.

Current sensors monitor the current going to the 3 phases of the motor. These sensors detect and alert when I have a short circuit or ground. Some manufacturers only test for a short circuit or ground at the first command to run the circuit. The process is supervised by some software that gives us an Alarm and there is a switch that disconnects the engine from the drive. Some inverters do not have this control resulting in damage to the motor in the event of a short circuit. Of course, a driver does not remove the other protections of the engine from overheating or overheating and they must coexist.

The Inverters, the IGBT and the snubber card are mounted on a heatsink under each of the 3 rows of capacitors.

All Drivers manufacturers use a PWM configuration with a different pulse width that goes to the engine.

Note :  Why we use IGBT:

The semiconductor we use is IGBT because it has a very fast response and can reach high frequencies.

The diagram above shows only 7 pulses on each side, but in reality, 1750 pulses or more should be displayed. This PWM frequency can range from 3.5 kHz to 15 kHz, which means it sounds. It is also known as carrier frequency, which is variable by most VFD manufacturers. A low carrier frequency can make annoying noise, but a higher carrier frequency produces more heat in the driver and engine. If the carrier frequency noise is very loud especially with the supply fans, LC filters are placed between the VFD and the motor and the noise stops in this filter.

Without a driver, the engine can run at full speed or be stopped. With a driver, the engine can go to a number of different speeds.

In the photo, we see a PWM configuration that goes to the motor without control and to the right with VVC + control by Danfoss.

The control and regulation unit monitors all 3 sections, making many calculations and corrections to the output signal. The test is performed with a PID controller and a 4-20 mA or 0-10 V sensor. The photos for the analysis of the Inverter circuits are from the large Inverters> 400Hp of the Danfoss company based in Denmark.

Troubleshooting on a VFD Driver

If we know what the components of a VFD Drive are made of, we can very easily find some damage by measuring dynamically with a multimeter.

Step 1: Check the input rectifier.

Before starting, do not forget to always turn off the power and wait until there is no voltage on the DC bus. Then measure the voltage drop across the diode-thyristor and it should have values ​​according to the manufacturer’s leaflet eg (0.3 V to 0.6 V) at each input terminal. One possible fault is that the entrance bridge is most likely short-circuited. However, if you read the open circuit with both + – or upside down terminals, then the charging resistor is probably open.

Step 2: Check the output of the VFD driver

Holding the red multimeter terminal on the “-“ negative bus, insert the black cable into each of the three motor output terminals. You will need to read again, a small voltage drop across the diode. Now, reverse the black cable on the positive “+” bus and the red cable on each motor output terminal. It will bring out a diode voltage drop upwards. If this does not happen in both cases then the output device is shorted. If you read an open circuit, then either the output device is damaged or the Bus fuse is open.

Step 3: Check the bus capacitors

First, physically inspect the capacitors for signs of damage, such as a cracked or deformed housing, or a pressure plug coming out of the top. Then set the multimeter to Ohm measurement and start measuring the resistance in the capacitor as shown in the Figure below. For a short-circuited capacitor, the multimeter will display a reading close to 0 Ohm. In this case, you should look for a short circuit. The only way to be sure of this is to put an oscilloscope on the Bus and watch the ripple.

Basic diagram for small Inverter motors of some Hp.

As we see in the photo above, the wiring of such an Inverter is very easy, a three-phase power supply and three cables power the motor. Many manufacturers allow us to connect three-phase motors with single-phase supply since the capacitor circuit that converts the single-phase network to three-phase is integrated into the board.

We also see that at inputs DI1, DI2, DI3 we can put the start of the motor Stop-Start, make a reversal in the motor but also get some error. We can also achieve variable speed regulation with analogue voltage 0-10 Volt or analogue current 0-20mA.

In the seminar that will be held in Athens in September, we will connect the Inverter with a PLC eg Logo8 and we will fluctuate the engine speed from the PLC