Question

If a small air-gap was made in the iron core of a transformer, thereby increasing the reluctance of the magnetic circuit, what eVect would it have on the following:

A. The no-load current, with the primary supplied at rated voltage.
B. The magnetising reactance.
C. The secondary voltage.

Answer 1

a) No-Load Current will increase

b) The magnetising reactance will increase

c) The secondary voltage will decrease

Step-by-step explanation:

a) when an air ap is made in the transformer core then more current is required for the magnetisation of core. Hence, no-load current will incraese.

b) with the air gap the magnetomotive force increases. As a result, the angle between the voltage and current increases. Consequently, power factor decreases. Power factor always decreases when the reactive behaviour of circuit incraeses. Hence, Magnetisation reactance will increase.

c) Secondary voltage decreases due to air gap. Therefore, it is said that with the air gap the efficiency of the transformer decreases.