REVIEW QUESTIONS If a splitphase motor has two poles on the

REVIEW QUESTIONS If a split-phase motor has two poles on the main winding, how many poles are needed for the auxiliary\' winding? (2) How many poles are there respectively on the running and the starting winding of an 8 pole split-phase motor? (4) Running Winding = poles. Starting Winding = poles Why is an auxiliary winding necessary\'? (4) Why must the auxiliary\' winding be different from the main winding in a split-phase motor? What would happen if the starting and running windings were identical?

Solution

1) Two auxiliary windings are needed for two poles

2) There are 8 poles formed by the starting winding and 8 poles formed by the running winding. It does not mean that the motor starts as a 16 pole motor and runs as an 8 pole motor.

3)A auxiliary winding, is used to create the torque needed to start a single phase induction motor. This winding creates the rotating magnetic field in this type of motor by changing the relationship between current and voltage.

4)A centrifugal switch is connected in series with the auxillary winding. Its function is to automatically disconnect the starting winding from supply when the motor has reached 70 to 80 percent of its full load speed. So auxillary winding is not permanent.

5) The current flowing through them would have beent he same and the angle of lag with the voltage would also have been same.