Power transformer working principle / function and loss

2019-05-17 12:17:02 JuKe Technology (DongGuan) Co., Ltd. Read

Power transformer working principle / function and loss

 How the Power Transformer works

Regarding the power transformer, it is a special transformer that shares a set of coils for output and input. Boost and buck are implemented with different taps. The portion of the tap voltage that is less than the shared coil is reduced. The portion of the tap voltage is higher than the shared coil. The working principle of the power transformer is to use the principle of electromagnetic induction. The alternating current we use generates a magnetic field through the coil N. There is a coil M beside the coil N. Since the magnetic field generated by the coil N is not constant, a corresponding change is made according to the change of the current. The change in the magnetic field causes a corresponding current to be generated in the coil M, wherein the frequency changes the frequency of the coil M according to the difference in the turns ratio of the coil N and the coil M. Of course, many power transformers now start to become single coils (called autotransformers), and the principle is basically the same.
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The autotransformer is a transformer with only one winding. When used as a step-down transformer, a part of the winding is extracted from the winding as a secondary winding. When used as a step-up transformer, the applied voltage is only applied to the winding-partial line. on. Usually, the part of the winding that belongs to both the primary and secondary is called the common winding, and the rest of the autotransformer is called the series winding. The autotransformer of the same capacity is not only small in size but also high in efficiency and transformer. The larger the capacity, the higher the voltage. This advantage is more prominent. Therefore, with the development of power systems, the improvement of voltage levels and the increase of transmission capacity, self-twisting transformers have been widely used due to their large capacity, low loss and low cost.
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 Power transformer function

In addition to the small size of the power transformer, there is no clear dividing line between the power transformer and the electronic transformer. Generally speaking, the power supply of the 60 Hz power network is very large, and it may cover a large capacity in half a continent. The power limitation of an electronic device is usually limited by the ability to rectify, amplify, and other components of the system, some of which are amplified power, but it still falls within the scope of small power compared to the power generation capability of the power system. Various electronic equipment is commonly used in transformers. The reason is: providing various voltage levels to ensure normal operation of the system; providing electrical isolation of parts with different potentials in the system; providing high impedance to alternating current, but providing low impedance to direct current; Maintain or modify the waveform and frequency response at different potentials.
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 Power transformer loss

In the power supply voltage device, when the current passes through the primary coil, a certain amount of heat is generated. (The magnetic flux generated by the coil flows in the iron core because the iron core itself is also a conductor, and is induced on a plane perpendicular to the magnetic line of force. Potential, this potential forms a closed loop on the cross section of the core and generates a current, as if it is a vortex, so it is called "eddy current." This "vortex" increases the loss of the transformer and causes the temperature rise of the transformer's core heating power transformer. Increase.) More energy loss is in the resulting "eddy current", which is the "iron loss" in the term. In addition, when a large amount of copper wire is used in our power transformer, a large amount of heat is generated when the current passes, which is what we call "copper loss." The main heat source of the power transformer is "copper loss" and "iron loss", and these two phenomena make the power loss of the power transformer more. Therefore, the temperature rise of the transformer is mainly caused by iron loss and copper loss. Since the power transformer has iron loss and copper loss, its output power is always less than the input power. For this reason, we introduce an efficiency parameter to describe this, η = output power / input power.

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