What are the types of single-phase induction motors?

Single-phase induction motor

This type of motor will operate in a single-phase power system and it would have a single voltage and current. In this type of motor, the single-phase will be split into two-phase currents so that a rotating magnetic field can be created. So by using the help of this magnetic field the rotor can be rotated. The single-phase induction motor is used in houses, shops, etc, while the three-phase induction motors are used in large industries where high power is required. The three-phase induction motor has a good power factor when compared to a single-phase induction motor. This device has only a single stator winding. The construction of a single-phase motor is so simple and its maintenance is less. These motors are reliable and easy to repair.

What are the features of single-phase induction motors?

  • It has one stator winding
  • It uses a single-phase power supply
  • It doesn’t self-start so it would need a device to start it
  • It is mostly used for 3-4 HP applications
  • It is used for household applications such as fans, washing machines, dryers

How does a single-phase motor constructed and how does a single-phase motor work?

The single-phase motor uses only single-phase power for their operation, mostly they are used in low power applications. The construction of this device is simple and they are easy to maintain. This motor works based on the induction principle and that’s why it is called an induction motor. The stator and the rotor are the major part of this device and the rotor is the rotating part while the stator doesn’t move. The rotor which is used here will be a squirrel cage rotor and it has a laminated iron core with many slots. Single-phase AC windings will be provided to the stator winding and because of this a magnetic field is created, The AC current will create an alternating flux and this flux will cut the rotor conductor and there would be an EMF generated in the rotor, so the rotor has closed circuit and there will be a current flow in the rotor and this current is called rotor current and this would produce a flux and it is rotor flux.

Why the single-phase induction motor is not self-starting?

As we discussed above the flux that is created is equal and opposite the AC current has created flux and it again creates a flux in the rotor and they rotate in the equal and opposite direction. The created flux has equal magnitude and because of this they will cancel each other and because of this, the net torque experienced by the rotor at the starting condition is zero.

What are the types of single-phase induction motors?

So the induction motors are not self-starting, so depending upon the way in which the motor is started the single-phase induction motor is divided into three types they are.

Split phase induction motor

The auxiliary winding is also called as starting winding and this winding will be made of thin wire and because of this, its impedance is different from that of the main winding. These windings will be connected parallel to the AC supply and there will be a phase difference between the two winding currents and this is proper to create a rotating magnetic field and thus the required torque for starting the motor is created.

Capacitor start motor

In this type the auxiliary windings have more turns, a capacitor will be serially placed with the auxiliary winding, and a centrifugal switch is also connected, and the two windings are placed 90 degrees. This type of motor is used in places where high starting torque is needed. This device has a main winding and a starting winding, the capacitor will be connected to the starting winding, current that flows in the capacitor will lead to the applied voltage by some angle. The current flowing in the running winding lags behind the applied voltage by an angle and this would result in large phase angle differences between these two currents and which will create the required current for motor starting.

Shaded pole motor

The stator of this type of motor has a projected pole and these poles are shaded by copper and it will be inductive. So when an AC power is applied to this an alternating flux is created, and the current created will be in a way that opposes the direction of the main flux. The shaded pole flux lags behind the unshaded pole flux and the phase difference between these two fluxes will create the required rotating flux.

What are the applications of a single-phase induction motor?

  • Washing machines
  • Vacuum cleaner
  • Mixers
  • Refrigerators
  • Hair driers
  • Fans

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