1. Manufacturing principle of transformer:

In the generator, no matter the coil moves through the magnetic field or the magnetic field moves through the fixed coil, the electric potential can be induced in the coil. In these two cases, the value of the magnetic flux is unchanged, but the number of the magnetic flux of the intersecting chain with the coil changes. This is the principle of mutual inductance. Transformer is a device that uses electromagnetic mutual inductance to transform voltage, current and impedance

2. In the circuit, the symbol of transformer is:

3. Technical parameters:

For example, the main technical parameters of power transformer are: rated power, rated voltage and voltage ratio, rated frequency, working temperature class, temperature rise, voltage regulation rate, insulation performance and moisture-proof performance. For general low-frequency transformer, the main technical parameters are: transformation ratio, frequency characteristics Nonlinear distortion, magnetic and electrostatic shielding, efficiency, etc

A. Voltage ratio:

V2 N2

--- = --- = n

V1 N1

The number of coils in two groups of transformer is N1 and N2 respectively. N1 is the primary coil and N2 is the secondary coil. When an AC voltage is applied to the primary coil, the induced electromotive force will be generated at both ends of the secondary coil. When N2 > N1, the induced electromotive force will be higher than the voltage applied to the primary coil. This kind of transformer is called voltage boosting transformer: when N2 < N1, the induced electromotive force will be lower than the primary voltage, The relationship between the primary and secondary voltage and the number of coils is as follows:

When n < 1, then N1 > N2, V1 > V2, the transformer is step-down transformer, otherwise it is step-up transformer

B. Efficiency of transformer:

At rated power, the ratio of output power and input power of the transformer is called the efficiency of the transformer, i.e

η= ( P2/P1) x100%

Where η For the efficiency of the transformer; P1 is input power, P2 is output power

When the output power P2 of the transformer is equal to the input power P1, the efficiency is improved η Equal to 100%, the transformer will not produce any loss. But in fact, there is no such transformer. When the transformer transmits electric energy, it always produces loss, which mainly includes copper loss and iron loss

Copper loss refers to the loss caused by the coil resistance of transformer. When the current is heated through the coil resistance, part of the electric energy will be converted into heat energy and lost. Because the coil is generally made of insulated copper wire, it is called copper loss

The iron loss of transformer includes two aspects. One is hysteresis loss. When the AC current passes through the transformer, the direction and size of the magnetic line of force passing through the silicon steel sheet of the transformer change accordingly, which makes the molecules inside the silicon steel sheet rub against each other and release heat energy, thus losing part of the electric energy, which is hysteresis loss. The other is eddy current loss. When the transformer is working, the magnetic line of force passes through the iron core, In the plane perpendicular to the magnetic line of force, the induced current will be generated. Because the current forms a closed loop and circulates, it is called eddy current. The existence of eddy current makes the iron core heat and consumes energy. This kind of loss is called eddy current loss.