Understanding Power Transformers: Functions, Types, and Working Principles

Do you know various kinds of transformers are used in electrical power management? Among the most important of these devices are power transformers. These transformers are used in almost all industries to step up or step down the required voltage levels. But even if they are commonly found in the industry, you may be wondering what exactly power transformers are and how they function.

So, we have created an informative article that explains every piece of information that one should have about electric power transformers including their functions, their classifications, and their operational principles.

1) What are Power Transformers?

A power transformer is a static device that connects two or more circuits and is capable of transferring electrical power between the circuits without changing the frequency. The device operates on an alternating current supply and does not have any moving/rotating components.

Power transformers come under three categories according to their use:

• Large Power Transformers: Generally 100 MVA and above in capacity.
• Medium Power Transformers: Approximately 100 MVA.
• Low Power Transformers: These are rated in the range of 500 to 7500 kVA.

To deliver voltage, a transformer is split into two parts where one section has a high current low voltage circuit and the other section has a high voltage low current circuit. The power transformer’s working can be controlled under Faraday’s law of induction that governs the power network implying that any power equipment connected to the power system operates at the rates allocated by the transformer.

➔  Delixi Power Transformers

We at Delixi aim to provide power transformers in all rated capacities, normally ranging from 30 KVA to 20,000 KVA. Our transformers are used for all indoor & outdoor uses. Our product is the SZ11-33kV Series Power Transformer.

This transformer is a beast built to operate with high efficiency and low loss of energy. When it comes to environmental conditions, it can withstand up to 1000 m above sea-level height, and air temperatures between  -45°C to +40°C.

2) Working Principle of Power Transformers

Generally, a transformer consists of two main windings: one is the primary winding and the second one is the secondary winding both of which are wound around the same magnetic core.

The working principle of the power transformer is based on Faraday’s law of electromagnetic induction. It states that a change in the magnetic flux through a coil creates an electromotive force (EMF) in the coil. This can be better understood in a few steps which are explained as follows:

Step 1) An alternating current (AC) passes through the primary winding of the transformer, it produces a time-varying magnetic field in the primary winding.

Step 2) The flow of magnetic flux proceeds through the core of the transformer, which interconnects primary and secondary windings.

Step 3) The change in a magnetic field induces a voltage in the secondary winding as per Faraday’s law of electromagnetic induction.

Step 4) The induced voltage is determined by the turns ratio which is the ratio of the number of turns of the secondary winding to the primary turns.

When the number of turns in the secondary winding is larger than the primary turns, it is said to be a step-up transformer. Unlike, a transformer decreases the voltage when secondary winding has less number of turns and is said to step down the voltage.

Step 5) Lastly, the power is transmitted through the secondary winding to the connected load.

3) Power Transformers Types

There exist some parameters by which power transformers can be grouped into classes. These parameters include;

• Based on the Core and winding design
• Based on the Turn ratio
• Bases on Phases
• Based on Core materials

➔  Based on Core and Winding Design

i) Berry-Type Transformers: These have been made in such a manner that the core looks like the spokes of a wheel with many independent magnetic circuits usually above two. The benefit of this is that it makes use of distributed magnetic circuits.

ii) Core-Type Transformers: The core is made up of two joined L-shaped steel strips which are stacked to form layers. When constructing transformers, continuous joints need to be avoided to help reduce the reluctance at the joints. The core’s limbs and yoke carry the magnetic flux.

iii) Shell-Type Transformers: In such transformers, the secondary and primary coils are completely enclosed by the metal core. An E-type and an I-type steel strip is layered to form the core. The central limb of the core carries the full amount of flux magnetism, while half the flux amount is handled by the side limbs.

➔  Based on Turns Ratio (Ns/Np)

iv) Isolation transformers: They have the same number of primary and secondary turns which equals to 1:1 ratio. Their basic function is to isolate the load from the power source. Often, these transformers are used with computers, measuring instruments, machines, medical devices, and other sensitive devices.

v) Step-Down Transformers: They have a turns ratio of less than one in such a case the number of turns in the primary is greater than in the secondary. They change an input which is high voltage and low current on the primary side into a low voltage high current output on the secondary side.

vi) Step-Up Transformers: The transformer normally has more turns in the secondary winding than the primary, thus the turns ratio is more than one. This design change takes low energy input amp at high voltage and converts it to low energy output at high current.

➔  Based on Phases

vii) Autotransformers: Autotransformers operate on a principle of self-induction through a cascaded multi-device multi-windings structure comprising a single turnover connected windings at various terminals to obtain any rating of a desired voltage without using a dedicated transformer. These are used in induction motors, urban transport networks, railways, audio, and assorted light turbo systems.

viii) Single-Phase Transformers: Such transformers have a single primary and secondary winding and thus have a single alternating voltage, the output which is a sine wave. These are designs that are commonly used in residential and light commercial requirements in suburban areas with less power demand.

ix) Three-Phase Transformers: Constructed of three pairs of primary and secondary windings, these transformers may be formed by the connection of three independent single-phase transformers, or the windings may be incorporated within a single laminated core. They produce a three-phase alternating current through several conductors. They are advantageous for the provision of power to heavy-duty motors,  and power distribution systems.

➔  Based on Core Material

x) Air Core Transformers: There is no physical core, and only the primary and secondary windings are insulated and wound into a solid material which in most cases is a dielectric material. Such transformers have a typical application in the radio frequency range and are suitable for a rigorous high-frequency operation.

xi) Ferrite Core Transformers: Cores are composed of ferrite material which is a form of ceramic material consisting of iron oxides together with other ingredients such as zinc nickel and manganese. Ferrite materials have low eddy current losses which allow high magnetic permeability which is why ferrite cores are used for high-frequency applications in electronics.

xii) Iron Core Transformers: Iron Core Transformers are constructed from laminated sheets of iron providing a very low magnetic reluctance. They are the most common type of transformers for several applications because of high-efficiency areas of magnetic flux.

xiii) Toroidal Core Transformers: Toroidal core transformers feature ring-shaped cores usually made of iron or ferrite, around which the windings are wrapped around. The structural configuration enhances coil efficiency by minimizing magnetic flux leakage and therefore maximizing inductance and Q factors. Toroidal transformers are readily used in telecommunications, power distribution, and industrial control systems.

4) Functions of Power Transformers

Transmitting and distributing electricity can be done quickly, safely, and even economically by utilizing power transformers. Below is a discussion of the general functions done by power transformers:

? Voltage Transformation:

• Step-Up Voltage: Power transformers at generating stations step up the voltages to quite high levels for far-distance transmission to minimize energy loss.

• Step-Down Voltage: Power transformers lower the voltages up to acceptable levels for safe transmission and distribution to homes, businesses, and industries at substations closer to customers.

? Isolation of Electric Circuits: Power transformers serve the purpose of segregating one part of the power system from the other by providing electrical isolation between the generating side and the distribution side.

? Power Transmission over Long Distances: Allows for the transfer of electricity over long distances with less technical losses by stepping up the voltage level at the generation and stepping it down at the distribution with the help of transformer action. This helps to provide a constant and reliable power supply.

? Keeping the System Stable and Efficient: Power transformers help in the stabilization of the power network by controlling voltage levels thus ensuring intelligent flow of electric energy and avoiding congestion of the transmission lines.

? Protection against Overload and Faults: Power transformers help protect against certain electric faults such as fuses, circuit breakers, and relays which can protect against overloads, short circuits, and other electrical faults. This type of protection can reduce the chances of transformer failure, loss of power supply, and the possibility of electrical fires and enhances the reliability of the system and the safety of the entire system.

? Adapting Power for Different Applications: Different transformers enable power supply characteristics to be adjusted according to certain parameters which may include high voltage used by industrial machines up to low voltage levels used by household appliances.

➔ Conclusion

Power transformers ensure our world works without any problems. They enhance the power transmission, cut down the energy loss, and make sure that factories, homes as well as other structures are powered. If you have ever thought about how electricity reaches your house or place of work, then thanks to the transformers who do this work in silence beforehand.

Whether you are working in the energy sector or are just interested, these devices are quite remarkable! And if you are looking to get one, Delixi has reliable, high-quality transformers that you can count on for the job. Try Delixi and feel the difference!