Electrical Engineering ⇒ Topic : Split-phase methods
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Sunita
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Split-phase methods When two windings which are displaced electrically by 900, carry currents with a phase difference of 900, they will produce a rotating magnetic field. In the circuit shown in Figure 1 (a) currents in the main winding and the auxiliary winding flowing in two sets of poles produce a sort of rotating magnetic field which starts the motor. The two currents Im and Ia (shown in Figure (b)) should differ in phase by 900, but this condition is not really obtainable and in fact, is not necessary. When the motor comes up to the speed, a centrifugal switch in the motor opens the switch S and disconnects the auxiliary winding. The starting torque in this case is very small. As such it is used in fans, blowers, duplicating machines, refrigerators, etc. Normally they are in the capacities of (1/30) H.P. to (1/20) H.P. Figure (1) Split-phase methods | |
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