Everything you should know about power transformers
By Yang Qiang
March 11th, 2025
349 views
- What is a power transformer?
- How does a power transformer work?
- Application scenarios ⊙ Substation ⊙ Copper Mine ⊙ Power Plant ⊙ Residential delivery
- Common voltage range of power transformers
- Conclusion
Power transformers contribute to the stable transmission of electricity. Their placement in the power grid has been carefully calculated to maximize distribution efficiency. Power transformers are used to efficiently increase or decrease voltage to the optimal level. This is necessary for long-distance safe transmission and distribution of electricity for household and industrial purposes at safer and lower voltages. Understanding the functions and various applications of these key devices is crucial, especially for professionals in the power industry.
1.What is a power transformer?
Power transformer is a static electrical equipment. It transmits power between circuits. It doesn't require any moving parts because it utilizes electromagnetic induction. It utilizes the principle of electromagnetic induction to effectively change the voltage level for power transmission or distribution. It consists of two or more coils connected by a common magnetic core. A power transformer consists of two coils. They are called primary winding and secondary winding. The winding is wrapped around the central laminated iron core. The iron core is made of stacked steel sheets. Its function is to concentrate and guide the magnetic flux lines generated by the current flowing through the winding coil. The entire magnetic and electrical components are installed in a steel tank filled with insulating oil. This oil is used for insulation and cooling of large power transformers during operation. In addition, larger utility transformers may contain other internal components such as bushings, cooling pipes, tap changers, and protective circuits for adjustment during power transmission.
2.How does a power transformer work?
The working principle of a power transformer is based on electromagnetic induction. The magnetic field in a circuit will induce voltage in nearby circuits. Specifically, due to the alternating current passing through the primary coil, the magnetic field generated in the primary coil changes, inducing voltage in the secondary coil wound around the same iron core. The conversion process inside power transformers is very interesting.
The steps involved include:
1. AC power passes through the primary winding. It establishes a changing magnetic field around the iron core of the transformer. This occurs due to the magnetic effect of electric current.
2. With the circulation of AC voltage, the magnetic field strength inside the iron core expands correspondingly in half of the cycle, and decays in the other half.
3. This continuously changing magnetic flux penetrates from the inner core and passes through the secondary winding wound around the same core structure.
According to Faraday's law of electromagnetic induction, when magnetic flux passes through the secondary winding coil, the changing magnetic field will generate an electromotive force (EMF) in the secondary winding coil.
The magnitude of induced electromotive force in the secondary depends on factors such as magnetic flux change rate, winding turns, and other transformer specifications. By adjusting the turns of the two windings, the turns ratio of the transformer can be used to increase or decrease the induced voltage in the secondary winding relative to the primary voltage.
The transformed voltage can be used for subsequent power transmission or distribution applications after passing through the isolated secondary winding.
3. Application scenarios: According to voltage conversion requirements, power transformers have various important application scenarios. They can achieve efficient power transmission in a vast network. Some of the most common uses of power transformers include: ⊙ Transformers in substations play a critical role in high-voltage transmission. Step up transformers can increase the distribution voltage for efficient long-distance power transmission through transmission lines. On the other hand, step-down transformers can reduce the transmission voltage in order to deliver electricity to urban areas through distribution lines. Due to the risk of fire and explosion underground, copper mines require specially designed isolation transformers. The coil components of these transformers are enclosed in a casing to prevent arc ignition in hazardous mining environments. In thermal and hydroelectric power plants, generators generate electricity at voltages suitable for efficient power generation, which may differ from transmission standards. Therefore, the power station transformer adjusts the voltage to the required transmission level and then sends it out through the transmission line. The pole mounted transformers installed on both sides of the street for residential delivery can help further reduce the distribution voltage and ensure safe use for households. The base type transformer installed on the ground of residential areas can perform similar voltage conversion functions and supply power to various residential loads.
4. Common voltage range of power transformers: The voltage range of power transformers is wide, depending on their capacity and intended use. The common voltage range of power transformers can be classified according to their purpose and the specific requirements of the power system they serve. Common power transformers ranging from 110kV to 750kV are crucial for power transmission and are mainly used for:
110kV power transformer: used for regional distribution, to step down higher voltages for industrial and commercial use.
220kV power transformer: suitable for long-distance transmission, connecting power plants and substations to minimize energy loss.
420kV power transformer: used in the main power grid for cross regional transmission of important power loads.
500kV power transformer: designed specifically for ultra-high voltage transmission lines, connecting major cities or provinces to ensure grid stability.
750kV power transformer: used for high-capacity, long-distance transmission lines, usually spanning countries or continents, to achieve efficient power transmission. These transformers are designed to reduce energy loss during long-distance transmission and ensure efficient and reliable power supply. A reputable power transformer manufacturer ensures the provision of high-quality products ranging from distribution level voltage to ultra-high transmission voltage. Shanghai Zhiyou Company is such a globally renowned supplier with years of experience in the energy field. You can visit our website to view all of our power transformers.
Conclusion: Power transformers play an indispensable but often overlooked role in achieving reliable transmission and distribution of global electricity. A deep understanding of the electromagnetic working principle, various deployment scenarios, and technical requirements of power transformers is of great benefit to professionals engaged in this field.
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