What is the starting torque of an induction motor?

Starting torque is the torque produced by induction motor when it starts. We know that at the start the rotor speed, N is zero.

Why does induction motor draw high starting torque?

The induction motor draws a high starting current as compared to the running condition. The current reduces as the motor accelerates towards its base speed or synchronous speed.

Why in induction motor gives high starting torque if the rotor resistance is high?

Slip ring induction motor has high starting torque. Because slip ring is connected through the resistance. When the supply is on the resistance is increases the phase difference is decrease due to this starting torque is increases.

Which type of motor has the lowest starting torque?

Abstract: Large single-phase motors (15-50 hp) have been developed. These are capacitor start-capacitor run squirrel-cage induction motors. They are designed with very low inrush current and have low starting torque.

Why the starting torque of squirrel cage induction motor is low?

It suffers from the disadvantage of a low starting torque. It is because the rotor bars are permanently short-circuited and it is not possible to add any external resistance to the rotor circuit to have a large starting torque.

What are the high starting torque IM?

In order to increase the starting torque, extra resistance should be added to the rotor circuit at start and cut out gradually as motor speeds up. The maximum torque is directly proportional to square of rotor induced emf at the standstill. The maximum torque is inversely proportional to rotor reactance.

Which motor has high starting torque and starting current?

The capacitor start motor develops a much higher starting torque of about 3 to 4.5 times of the full load torque.

What effect does rotor resistance has on the starting torque of induction motor?

From Fig. 7.14, a high rotor resistance will provide a high starting torque, leading to rapid acceleration of the mechanical system. This is desirable because short acceleration times reduce the stress on the power system caused by high starting currents.

Which motor gives higher starting torque?

How do you find the starting torque of an induction motor?

Starting Torque Of Induction Motor. At the start condition the value of s = 1. Therefore, the starting is obtained by putting the value of s = 1 in the equation (6), we get. The starting torque is also known as Standstill Torque. At synchronous speed, s = 0 and hence developed torque Ʈd = 0. At synchronous speed, developed torque is zero.

How to start an induction motor with reduced voltage?

The motor can also be started by applying a reduced voltage to the motor when the motor is started. The torque of the induction motor is proportional to the square of the applied voltage.Thus, a greater torque is exerted by a motor when it is started on full voltage than when it is started on the reduced voltage.

How to increase the starting torque at low speed?

Internal Rotor Resistance – The across the line starting torque at low speed can be increased by increasing the rotor resistance. This will decrease the efficiency of the motor, and the heat on the rotor.

What is a lower pull up torque?

A lower Starting Torque can be accepted for centrifugal fans or pumps where the start load is low or close to zero. The Pull-up Torque is the minimum torque developed by an electrical motor when it runs from zero to full-load speed (before it reaches the break-down torque point).