Introduction

In the previous chapter we got a brief idea of electric machine. In case of a generator, the mechanical input is transformed into electrical output via a magnetic circuit whereas in case of a motor the energy flow is just reversal. But they all transform one energy form to another energy form via magnetic transformation. It will not be very wrong if we call all machines are transformers. But in electric engineering we exclusively specify a special type of electric (static) machine as the transformer. A motor or a generator transforms the electrical energy to mechanical energy and vice-versa. We have seen the energy flow diagram of these in Fig. 8.1a and Fig. 8.1b. In these cases the quality of the energy parameters is completely transformed. We get mechanical energy parameters, like torque and speed transformed as electrical parameters like voltage and current in generator. We get the reversed effect in motor. Transformer is such a static machine that transforms one form of electrical energy to another form of electrical energy. There is no qualitative transformation in the energy parameters. We obtain voltage and current output from voltage and current input. Only the quantity of the parameters get changed due to this transformation. That is, the input voltage level is different from the output voltage value in a transformer. Being a non-perpetual machine the transformer ought to follow the energy conservation law. The electric energy is measured by the product of voltage and current. Thus, in a transformer V×I of input side should be equal to the V×I of the output side.