Transformer is a kind of electrical equipment used for electric energy conversion. It is an indispensable and important device in the power grid. It can convert alternating current energy of one voltage and current into another alternating current of voltage and current of the same frequency. Transformers are used in all electronic products. Its principle is simple, but the winding process of the transformer will have different requirements according to different use occasions (different uses). The functions of the transformer mainly include: voltage transformation; impedance transformation; isolation, voltage regulation (magnetic saturation transformer), etc., The core shapes commonly used in transformers are generally E-type and C-type cores.

In different environments, transformers are used for different purposes, such as:

1. Raising the voltage during long-distance transmission can reduce the power loss on the line;

2. When reaching the area of use, reducing the voltage can meet the electricity demand of different users;

3. The use of transformer connection during impedance matching can play a role in changing the impedance;

4. The use of isolation transformers can electrically isolate the two phases to prevent electric shock accidents.

The working principle of the transformer:

The transformer consists of an iron core (or magnetic core) and a coil. The coil has two or more windings. The winding connected to the power supply is called the primary coil, and the rest of the windings are called secondary coils. It can transform AC voltage, current and impedance. A simple iron core transformer consists of an iron core made of soft magnetic material and two coils with different turns on the iron core. The function of the iron core is to strengthen the magnetic coupling between the two coils. In order to reduce the eddy current and hysteresis loss in the iron, the iron core is laminated by lacquered silicon steel sheets; there is no electrical connection between the two coils, and the coils are wound by insulated copper wire (or aluminum wire). One coil connected to the AC power supply is called the primary coil (or primary coil), and the other coil connected to the electrical appliance is called the secondary coil (or secondary coil). The actual transformer is very complex, and there are inevitably copper loss (coil resistance heating), iron loss (iron core heating) and magnetic leakage (magnetic induction line closed by air), etc. The ideal transformer is established under the conditions: ignore the leakage magnetic flux , ignoring the resistance of the primary and secondary coils, ignoring the loss of the iron core, and ignoring the no-load current (current in the secondary coil open circuit primary coil). For example, when the power transformer is running at full load (the secondary coil outputs rated power), it is close to the ideal transformer condition.