Why does induction motor draw high starting torque?

Why does induction motor draw high starting torque?

The induction motor draws a high starting current as compared to the running condition. The starting current of the induction motor is about 5 or 6 times the motor full load current. The current reduces as the motor accelerates towards its base speed or synchronous speed.

Why is the starting torque of a wound rotor motor higher per ampere of starting current than that of a squirrel cage motor?

The rotor of a squirrel cage motor is constructed of bars connected together at each end by shorting rings. It has a higher starting torque per ampere of starting current than any other type of three-phase motor. It can be started in multiple steps to provide smooth acceleration from 0 RPM to maximum RPM.

Which induction motor has the highest starting torque?

Capacitor-start motor
2. Capacitor-start motor: The capacitor-start motor develops a much higher starting torque, i.e. 3.0 to 4.5 times the full-load torque.To obtain a high starting torque, the value of the starting capacitor must be large, and the resistance of starting winding must be low.

Which single phase motor is fitted with a wound rotor?

Chapter 13 – AC Motors. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. However, no power is applied to the slip rings.

How do you reverse wound rotor motor?

Reversing Rotation The direction of rotation of a wound-rotor induction motor is reversed by inter changing the connections of any two of the three line leads, figure 10. This procedure is identical to the procedure used to reverse the direction of rotation of a squirrel-cage induction motor.

How does a wound rotor motor increase torque?

During starting, this resistance is placed in series with the rotor windings. This added resistance causes the rotor current to run more in phase with the stator current, which increases the torque that is developed.

How does adding resistance to a wound rotor induction?

Adding resistance to a wound rotor induction motor does not reduce the maximum torque. The torque at a given slip decreases. The phase angle difference may be reduced slightly because the ratio of rotor reactance to rotor resistance is reduced slightly.

How does a wound rotor motor work in a squirrel cage?

By increasing the resistance in the rotor via the slip rings, the pullout torque can be achieved at much lower speeds, allowing higher initial torque and lower starting current. When reaching synchronous speed, the rotor resistance can also be shorted, making the wound rotor motor behave as if it was a squirrel cage motor.

Why is the torque peak higher with no rotor resistance?

Note that this torque peak is much higher than the starting torque available with no rotor resistance (R 0) slip is proportional to rotor resistance, and pullout torque is proportional to slip. Thus, high torque is produced while starting. The resistance decreases the torque available at full running speed.