In a split-phase motor

In a split-phase motor

Right Answer is:

The starting winding is connected through a centrifugal switch


In a split-phase motor, the starting winding is connected through a centrifugal switch.

Split-Phase Induction Motor

  • The main components of the split-phase motor include main winding, auxiliary winding, and a centrifugal switch.
  • This is the simplest way to establish a rotating magnetic field with two windings in the same stator core.
  • The auxiliary or starting winding has a series of resistance that makes its impedance highly resistant.
  • It is not the same winding as the main winding but has fewer turns of a much smaller diameter than the main winding.
  • This will reduce the voltage lagging of the starting current.
  • The main winding is inductive in nature to lag the voltage by a certain angle. This winding is designed to operate at synchronous speeds of 75% and above.

  • These two windings are connected to the input AC supply in parallel.
  • Because of the inductive nature, the supply voltage lags at a large angle, with the current induced by the starting winding almost being in phase with the voltage due to its resistive nature. Thus, there is a phase difference between these currents. The resulting current produces a rotating magnetic field and thus the starting torque.
  • The centrifugal switch is connected to the starting winding in series.
  • When the motor is 75-80% of the synchronous speed, the centrifugal switch is opened mechanically, thereby removing the auxiliary winding. The motor, therefore, only works with the main winding.
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