Transformers (Fig. 2.109) are static, passive devices that transfer electrical energy from one or multiple electrical circuits to another through the principle of mutual induction. Transformers are used to safely and efficiently isolate as well as increase or decrease AC voltage and current in electrical control systems.
A transformer has a primary and secondary coil (winding) that are wound around a common, laminated iron core. The primary coil is the input that draws power from the source. The second-ary coil is the output that delivers the energy at the transformed or changed voltage to the load.
The primary coil is connected to the power source and produces a magnetic field, which is concentrated around the iron core. Since the supply voltage is constantly changing, the magnetic field is also varying which will, therefore, induce a corresponding voltage in the secondary coil to the load. Electrical energy is transferred between the primary and secondary coils without a physical, conductive connection between the two. Except for minor heat-generated losses, the power in the secondary coil of a transformer is the same as the power applied to the primary coil.
A step-up transforme...