Introduction to Transformer principles

A transformer consists of an iron core (or magnetic core) and a coil. The coil has two or more windings. The windings connected to the power supply are called primary windings. The rest of the windings are called secondary windings. It can change AC voltage, current and impedance. A simple core transformer consists of a core made of soft magnetic material and two coils with different turns. The function of the core is to strengthen the magnetic coupling between the two coils. To reduce eddy current and hysteresis losses in the iron, the core is made of painted silicon steel sheets laminated; there is no electrical connection between the two coils, which are made of insulated copper (or aluminum) wires.

One coil connected to the AC power supply is called the primary coil (or the original coil) , and the other coil connected to the appliance is called the secondary coil (or the secondary coil) . The actual transformer is very complex, inevitably there are copper loss (coil resistance heating) , iron loss (core heating) and magnetic leakage (by air closed magnetic induction line) , etc. , the conditions of ideal transformer are: ignoring leakage flux, the resistance of primary and secondary coils, the loss of core, and the no-load current. For example, the power transformer in full load operation (sub-coil output rated power) is close to the ideal transformer situation.