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The efficiency of transformer

At rated power, the ratio of the output power of the transformer to the input power is called the efficiency of the transformer, ie
Where is the efficiency of the transformer; P1 is the input power and P2 is the output power.
When the output power P2 of the transformer is equal to the input power P1, the efficiency η is equal to 100% and the transformer will not produce any loss. But in fact this kind of transformer does not exist. Losses are always generated when the transformer transmits electrical energy. This loss mainly includes copper loss and iron loss. Copper loss is the loss caused by the resistance of the transformer coil. When current is generated by the coil resistance, a portion of the electrical energy is converted into thermal energy and lost. Since the coil is generally wound by an insulated copper wire, it is called a copper loss.
The iron loss of the transformer includes two aspects. One is the hysteresis loss. When the alternating current passes through the transformer, the direction and magnitude of the magnetic field lines passing through the silicon steel sheet of the transformer change, so that the internal molecules of the silicon steel sheet rub against each other, releasing heat energy, thereby losing a part of the electric energy, which is the hysteresis loss. . The other is eddy current loss when the transformer is working. The magnetic core has a magnetic flux passing through it, and an induced current is generated on a plane perpendicular to the magnetic line. Since this current forms a circulating current in a closed loop and is spiraled, it is called an eddy current. The presence of eddy currents causes the core to heat up, consuming energy, and this loss is called eddy current loss.
The efficiency of the transformer is closely related to the power level of the transformer. Generally, the higher the power, the smaller the ratio of loss to output power, and the higher the efficiency.Contrary, the lower the power, the lower the efficiency.