Question

a) Explain briefly why the core of most power transformers is made out of a magnetic material such as steel rather than wood. b) What would be the best type of motor for the following applications? 1. Driving a pump that always operates at full load? 2. A machine tool that requires precise speed or position control? c) Explain briefly when it would be optimal to produce power from a hydroelectric power plant with a large reservoir? d) Give two reasons why combined cycle gas turbines achieve a very high efficiency.

Answer 1

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A) Amount of power transfer from primary to secondary depends on the amount of magnetic flux flowing in the core. As wood is non magnetic core then amount of exciting current required will be very high to establish same amount of flux. This excessive current increases copper losses and hence heat is increased. This will damage the transformer.

If we use magnetic material then amount of exciting current required will be less and transformer will be in safe operating region.

That is why we use magnetic material for power tramsformers.