Tag Archive for: transformer

Transformer breakdown: what do thermal classes mean and how do they affect performance

by

Transformers provide power transmission and distribution between different voltage levels. Their reliability and longevity depend not only on the design and type of core or winding used, but also on their ability to withstand the heat generated during operation. In the following sections, we will therefore look at the division of transformers according to thermal classes.

Thermal classes of transformers

The thermal class of the transformer represents the maximum operating temperature of the insulating material at which the equipment can operate safely without risk of damage. This parameter is defined by international standards and is a key element in determining the lifetime and reliability of the equipment.

Insulating materials have different heat resistance. Therefore, the thermal class of the transformer is directly related to the type of materials used for winding and core insulation:

  • The higher thermal class allows the transformer to operate at higher temperatures, which can be advantageous in higher load applications or with frequent load fluctuations.
  • A lower thermal class, on the other hand, means that the transformer operates at lower temperatures and its lifetime may be shorter under the same operating conditions.

Division of transformers by thermal class

According to international standards, transformers are classified into several thermal classes, which determine the maximum permissible operating temperature of their insulating materials. The most common classes are:

  • Thermal class A ( maximum operating temperature 105 °C): mainly used in oil-immersed transformer types. These are materials with lower heat resistance, suitable for applications where less heating is expected.
  • Thermal class B ( maximum operating temperature 130 °C): commonly used in industrial equipment and network switchgear. Provides a balanced combination of durability and resistance to thermal loads.
  • Thermal class F ( maximum operating temperature 155 °C): used in dry or epoxy transformers with higher loads or where larger thermal peaks occur. It increases the resistance of the equipment and extends its lifetime in heavy duty applications.
  • Thermal Class H ( maximum operating temperature 180 °C): designed for special transformers or applications with extreme thermal loads. Guarantees maximum safety and long service life even at very high operating temperatures.
insulation of transformers

Types of transformers and their thermal specifications

Transformers can be divided into several main types according to design, cooling method and purpose. For each of these, the thermal class is a key parameter influencing performance, safety and lifetime:

  • Dry transformers: They use air or other gases to cool the windings. These transformers are most commonly manufactured in thermal class F, but also occur in class H. They are recommended for areas with high safety requirements, such as schools, hospitals, offices, and are also suitable for industrial applications due to their higher durability.
  • Oil TransformersA: They use transformer oil as a refrigerant and insulating material. The thermal class is normally A or B. They are ideal for distribution networks. The oil also serves as an insulating material, which increases the safety and life of the transformer.
  • Special transformers: They are used by critical applications, high power or industrial equipment. Thermal class A to H, often with special cooling systems (e.g. oil circulating or forced cooling). They are used where maximum reliability and minimized downtime are essential.
  • Transformers for RenewablesA: Designed for solar, wind and other renewable energy sources. They often combine dry or oil-immersed construction with thermal class A to F depending on power rating and load intensity. They have to cope with power fluctuations and adapt to intermittent renewable energy generation. Intelligent temperature control systems help prevent overheating and optimize transformer life.

Effect of thermal class on performance and safety

The thermal class of the transformer has a direct impact on its operating performance, service life and safety. A higher thermal class allows the transformer to operate at higher loads without the risk of overheating. Overloading below the thermal capacity, on the other hand, can lead to increased losses and reduced efficiency. It is the optimally selected thermal class that allows the energy to be distributed efficiently even under fluctuating loads.

Transformer insulation materials degrade faster at high temperatures, so the closer the operating temperature is to the maximum thermal class, the faster the insulation aging occurs. Proper selection of the thermal class therefore extends the life of the equipment. The thermal class also determines the maximum safe operating temperature, thus protecting the transformer from overheating and possible failures. An improperly oversized transformer can cause a risk of fire or grid failures.

insulation materials

Only transformers with a suitable thermal class can operate stably under different operating conditions.

Practical recommendations from professionals

When selecting, consider the type of transformer, its design, installation location, expected operating load and specific conditions such as industrial environment or integration with renewable energy sources. When planning and upgrading electrical networks, select transformers not only according to power and winding type, but also according to thermal specifications. Taking thermal classes into account helps to prevent overheating, outages and faults, thereby improving the safety and reliability of the entire system.

Transformation ratio: how it works and why it is important

by

In order for a transformer to effectively change the voltage between different parts of the network in electricity transmission and distribution systems, it must have a well-defined transformation ratio (also called transformer conversion). This is a fundamental parameter of any transformer. It determines how the voltage changes between its input and output, i.e. between the primary and secondary windings.

Transformation ratio

The transformation ratio represents the ratio between the number of turns on the primary coil and the number of turns on the secondary coil of the transformer. It determines how the electrical voltage changes as it passes through the transformer. It is denoted by the letter k . In practice, it is often also referred to as the ratio of input to output voltage.

Two basic types of transformers according to transformation ratio

The transformation ratio is a basic indicator of how a transformer adapts its electrical parameters to the requirements of a particular device or network:

  • Step-down transformer (k > 1): it is used to reduce the voltage. An example is an adapter that converts 230 V to 12 V for household appliances.
  • Step-up transformer (k < 1): used to increase the voltage, for example when transferring electricity from sources to grids.
installation of modern transformer

For decades, BEZ TRANSFORMÁTORY has been manufacturing quality transformers that accurately reflect the requirements for the correct transformation ratio from distribution networks to industrial applications.

See our current offer or contact us for a customized transformer design.

How is the transformation ratio calculated?

The calculation of the transformation ratio is simple. As we have already indicated, the transformation ratio is expressed either by the number of turns on the windings or by the voltages. The two expressions are mathematically equivalent: k = U₁ / U₂ = N₁ / N₂, where:

  • k = transformation ratio
  • U1, U2= voltages on primary and secondary windings
  • N1, N2= number of turns on primary and secondary windings
transformation concept, scheme

Transformation ratio and its importance in practice

The correct setting of the transformation ratio has a major impact on the operation of electrical equipment and entire distribution networks:

  • Efficient power transmission: in long-distance power transmission, voltage boosting is used with the help of transformers with a low transformation ratio. This makes it possible to reduce the current and thus the line losses. For distribution to households, the voltage is again reduced using step-down transformers.
  • Voltage adaptation for different equipment:With the right transformation ratio, we can adapt the output voltage of electrical equipment so that it operates safely and reliably.
  • Measurement and protection systems:Current and voltage transformers enable high voltage currents to be monitored safely by transforming them into smaller measurable values using a precisely defined transformation ratio.
  • Industrial and special applications: Special transformers with atypical transformation ratios are often used in industry . They allow specific voltage levels for machines, lines or laboratory instruments. This is because without the correct transformation ratio setting, these devices would not be able to function.
transformer failure

The transformation ratio is therefore a key parameter of any transformer and determines how the voltage between the input and output of the device changes. Its correct understanding and calculation are essential in the design, set-up and safe operation of electrical systems.

If you are looking for a reliable partner for the design and manufacture of customized transformers, take a look at the offer of BEZ TRANSFORMÁTORY, a leader in power solutions.

How the transformer works: a simple explanation for everyone

by

Even if you don’t know how a transformer works, it would be hard to imagine your life without one. Yet many people don’t know what it is and how it actually works. That’s why today we’ll explain the principle of its operation in a simple and understandable way. We will look at the basic processes that take place in it and show you its practical use.

The principle of operation of the transformer

The transformer changes the electrical voltage. It can either increase or decrease it. Its basic parts include coils of aluminum or copper wire, called primary and secondary windings. Between them is a metal core, usually made of mild steel.

When an alternating electric current is applied to the first coil (primary winding), a magnetic field is created around it. This magnetic field travels through the metal core of the transformer to the second coil (secondary winding) where the changing magnetic field “touches” the conductor and causes a new electric current to appear in it. This is called induction. Depending on how many turns the second coil has compared to the first, the voltage will either increase or decrease.

This phenomenon is described by Faraday’s law of electromagnetic induction, which states that “a change in the magnetic field over time induces an electric voltage in the coil”. This means that the transformer only works with alternating current because direct current would not create the changing magnetic field needed for induction.

This way the transformer changes voltage without anything moving in it. The whole process is based on a magnetic field and alternating current.

transformer

How the transformer and its individual parts work

The transformer has two main windings. The primary winding is the part that receives the electric current from a source such as a power plant. The secondary winding passes the treated voltage to where we need to get it, for example to household appliances. The two windings are wound from copper or aluminium wires and separated from each other so that the electric current cannot flow directly, but only through the magnetic field in the core.

The core is a metal part, most often made of steel or iron, which is placed between the windings. Its function is to conduct the magnetic field generated in the primary winding to the secondary winding. Thanks to the core, the magnetic field is concentrated and the transformer operates efficiently.

Types of transformers

In practice, we encounter various types of transformers, which differ in design and application:

  • Dry transformers have an air-cooled core and windings. They are mainly used indoors or where cleanliness and safety are important, such as in hospitals or offices. They are more environmentally friendly as they do not contain oil, but have lower maximum outputs.
  • Oil Transformers are filled with insulating oil, which helps to cool the windings and insulate them at the same time. They are mainly used in large substations and high power applications as the oil improves heat dissipation and reduces the risk of overheating.
  • There are also special transformersthat are designed for specific purposes, for example, interconnecting, three-winding, inverter, single-phase, excitation or earthing transformers.
  • Many are also adapted to work with solar panels, wind turbines or other sources. Transformers for renewable energy sources supply electricity with specific parameters and help to connect these sources to the grid correctly.
transformer

Practical use of transformers in electrical networks

Transformers safely and efficiently transmit electricity from power stations to our homes. This is because electricity is generated in large, high-voltage power stations to minimise losses in long-distance transmission. However, when it comes closer to where we want to use it, substations have to reduce its voltage to a level that is safe for homes or industry. This allows us to plug in appliances such as a TV, computer or fridge at home without worrying about anything going wrong.

BEZ TRANSFORMÁTORY, we could not…

… use common household appliances, as most of them need low voltage.

… to transmit electricity over long distances without huge losses.

… to work safely with high voltage in industry or power industry.

Understanding the basic principle of how a transformer works helps us to better understand how important these devices are in our daily lives. Even if we don’t see them, modern society could not function without them.

Electricity distribution: the role of transformers

by

Today we take electricity for granted. We flick a switch and a light comes on, turn on an appliance and everything works. But have you ever thought about the system behind this everyday convenience? From the moment energy is generated in a power station to the moment it powers your home, office or industrial operation, it goes a long way, and the distribution network is the invisible infrastructure that makes it all possible. Transformers are one of the most important links in this chain. Without them, the transmission of electricity over long distances and its safe distribution to end consumers would not be possible. Let us therefore look in more detail at the role of transformers in the distribution of electricity.

What are transformers and why are they key in distribution

Electricity is generated in power stations, often far from where we really need it. In order to minimise energy losses when electricity is transmitted over long distances, it must first be transformed into high voltage. This is what allows efficient transmission without significant losses due to the resistance of the conductors in the lines.

On the other hand, when the electricity gets close to the point of consumption, this high voltage needs to be reduced again to a level that can be handled by household appliances. This conversion is provided by transformers in distribution substations or directly at residential and industrial premises.

Transformers change electricity from technically efficient and high-voltage to normal and safe electricity that we can use. Without their constant work, the modern electricity grid would literally be non-functional.

Voltage boosting: efficient transmission from power plants

Immediately after the generation of electricity in power stations, transformers come into play to raise the voltage from the level at which the electricity is generated to much higher values. Higher voltages mean lower current for the same power, which in practice means less line losses.

Voltage reduction: safe energy for everyone

When the electricity gets close to the point of consumption, step-down transformers located in substations and local transformers come into play. Different voltage levels have different uses. Medium voltage is used in large industrial plants, low voltage is more likely to be used in homes, shops and offices.

transformer station

In addition to voltage transformation, transformers also provide galvanic isolation of different parts of the network. This reduces the risk of fault propagation and increases the overall safety of the system.

Voltage adaptation for specific needs

Not all devices operate at normal voltages. Some technologies, such as medical devices, data centres or specialised production lines, need stable and precisely defined voltages. Optimum functionality and protection of sensitive equipment is ensured by transformers that allow precise voltage adjustment.

BEZ TRANSFORMÁTORY is one of the most important players in the production and supply of transformers for distribution networks. It supplies transformers ranging from several tens of kVA to MVA units.

The future of electricity distribution and the role of transformers

Transformers will continue to play an indispensable role. From rooftop solar panels to wind farms and battery storage, transformers ensure the right voltage level in every part of the grid, contribute to power stability and security, and enable the efficient integration of diverse energy sources. Indeed, there is increasing talk about the need to integrate renewable energy sources.

transformers for renewable energy

In addition, the growing demand for electricity is placing increasing demands on distribution infrastructure. These challenges require smart, flexible and reliable distribution networks. That’s why BEZ transformátory is developing equipment with higher energy efficiency and meeting the European Union’s stricter standards for energy losses. It develops many flexible solutions that can adapt to specific conditions, thus becoming not only an equipment supplier but also a strategic partner in the process of energy modernisation.

If you too are looking for expert solutions in the field of electricity distribution, contact us. We offer oil-immersed and dry-type transformers that find application in standard distribution networks as well as in industrial and energy-intensive plants.

When to choose epoxy and when to choose oil transformer

by

Choosing the right transformer is not just a technical matter, but a decision that will affect its safety, maintenance and long-term operating costs. The most common types of transformers include epoxy and oil-immersed transformers. But when to choose which one? Let’s take a look at their advantages, disadvantages and the situations in which they are best applied.

What sets them apart

The oil-immersed transformer is filled with a special insulating oil that dissipates heat while insulating the internal components of the equipment.

The epoxy transformer has windings flooded with epoxy resin, it does not need any liquid, so it is often referred to as dry-type.

When to opt for an epoxy transformer

This type is ideal wherever safety, cleanliness and ease of operation are a priority. We recommend it for buildings where people move around, such as shopping centres, hospitals, schools and offices. It is used in interiors with limited space and a requirement for low noise levels, but also in places with strict fire and environmental standards.

There is no risk of oil leakage and the fire risk is also lower than that of an oil-immersed transformer. The epoxy transformer features minimal maintenance requirements and installation is simple and quick. However, the purchase price can be higher and the performance also has its limitations.

V BEZ TRANSFORMÁTORY We manufacture dry-type transformers with a capacity of up to 10,000 kVA and a maximum equipment voltage of up to 36 kV. Due to their high seismic resistance and low power losses, these devices are also suitable for harsh environments.

When to choose an oil transformer

Oil-immersed transformers offer high performance and are suitable for harsher outdoor environments. They are part of substations, energy-intensive industrial plants and locations where heavy loads or extreme climatic conditions are expected. High performance goes hand in hand with efficient cooling. With proper maintenance, the oil transformer is characterized by a long service life.

However, there is a higher risk of fire, so regular maintenance is always advisable, whether it concerns checking the oil or the filter systems. In addition, it is not suitable for confined spaces in buildings.

oil transformer

Company BEZ TRANSFORMÁTORY is one of the leading manufacturers of oil-immersed transformers in Central Europe with more than 120 years of history. It manufactures distribution transformers with outputs from 25 kVA to 16 MVA and with maximum equipment voltages up to 38.5 kV. They are characterized by maintenance-free operation, high reliability, the possibility of using environmentally friendly dielectrics and energy efficiency.

Quick comparison

In conclusion, both dry (epoxy) and oil-immersed transformers from our company represent the top in their category. However, the choice between them depends mainly on the specific application and operating environment.

Epoxy transformers are characterized by their high level of safety, minimal maintenance and compact design, which will be appreciated in interiors, commercial buildings, hospitals or data centers. Thanks to the advanced epoxy resin potting of the windings, they can withstand moisture, dust and vibration and do not pose a risk of liquid leakage.

On the other hand, oil-immersed transformers are superior in robustness, higher performance and excellent cooling. This makes them ideal for industrial plants or power distribution networks.

Simply put, if you are looking for a maintenance-free and safe solution for your building, choose a dry-type transformer. However, if you need high performance and operation in harsh or outdoor environments, reach for an oil-immersed one. In either case, however, you can rely on the company’s quality and experience BEZ TRANSFORMÁTORY.

manufacture of epoxy transformers

With more than 120 years of history, modern production facilities and exports to dozens of countries around the world, we are one of the leaders in Central Europe. We specialize in the production of both oil and epoxy transformers that meet the most stringent technical and environmental standards. We are able to adapt our solutions to different sectors, from industry and energy to renewables and public buildings.

So if you are looking for a reliable partner in the transformer field, contact us. With us, you get a long-term partner with a strong focus on reliability, safety and lasting value.

We are the only manufacturer of distribution transformers in Slovakia with more than 120 years of experience and a design life of 30 years.

Products

Oil Transformers

Dry transformers

Special transformers

Transformers for renewable energy sources

Links

References

Downloads

Careers

Contact

Contact

Rybničná 40, 835 54

Bratislava

+421 918 777 778

Certifications:

ISO 9001 certificate

ISO 14001 certificate

ISO 45001 certificate

Cookie Policy | GDPR | Terms and Conditions

©2025 BEZ TRANSFORMÁTORY