Working principle of 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 winding, and the remaining windings are called the secondary winding. It can transform AC voltage, current and impedance. The simplest iron core transformer consists of an iron core made of soft magnetic material and two coils with unequal turns sheathed 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 with painted silicon steel sheets; there is no electrical connection between the two coils, and the coil is wound by insulated copper wire (or aluminum wire). One coil connected to AC power 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 complicated, and there are inevitably copper loss (coil resistance heating), iron loss (iron core heating) and magnetic leakage (magnetic induction line closed by air), etc. In order to simplify the discussion, only the ideal transformer is introduced here. The conditions for the establishment of an ideal transformer are: ignoring the leakage flux, ignoring the resistance of the primary and secondary coils, ignoring the loss of the core, and ignoring the no-load current (the current in the primary coil when the secondary coil is open).