What happen to an induction motor when resistance will be added up in rotor side?

What happen to an induction motor when resistance will be added up in rotor side?

Adding External Resistance on Rotor Side The three-phase induction motor operates in a low slip region. Now if we increase rotor resistance, R2 torque decreases but to supply the same load torque must remain constant. So, we increase slip, which will further result in the decrease in rotor speed.

When the rotor resistance is high the speed of the induction motor is?

The larger the value of the resistance, the larger will be the value of the slip at which the maximum torque occurs. If the resistance of the motor is increased, then the pull-out speed of the motor decreases. But the maximum torque remains constant.

What happens when rotor resistance changes?

7.14 shows how the motor torque-speed curve would change if rotor resistance is increased and all other parameters in the motor equivalent circuit stay the same. While high starting torques are desirable, high rotor resistance results in a relatively high slip during normal running operation.

How does the external resistance of slip ring induction motor influence the motor performance?

Effect of Adding External Resistance The external resistance reduces high resistance as soon as the motor obtains normal speed and increases the starting torque of a motor. The tweaking of external resistance also aids in decreasing of rotor and stator current but improves the power factor of a motor.

What will happen in induction motor if we increase the air gap flux?

Detailed Solution. If the air gap of an induction motor increases, 1) The permeability of the magnetic circuit rotor-to-stator will decrease. 4) The magnetic flux in the air gap will decrease and leakage fluxes will increase; This will cause a reduction in the maximum available torque.

How does speed change with rotor resistance?

If the resistance in the rotor circuit is increased, the slip is increased and the speed of the rotor is decreased. This method is applicable only to wound rotor induction motor. From the figure 1 it is clear how does the speed vary with the change of rotor resistance.

What is the range of clearance that can be left between rotor bars and the core?

The range is usually chosen between 0.15-0.4 mm.

How does slip Help for rotation of induction motor?

“Slip” in an AC induction motor is defined as: As the speed of the rotor drops below the stator speed, or synchronous speed, the rotation rate of the magnetic field in the rotor increases, inducing more current in the rotor’s windings and creating more torque.

Which starter is used for slip ring induction motor of high rating?

Rotor resistance starter
Rotor resistance starter is used for slip ring induction motors of high ratings.

How is the speed of a slip ring motor controlled?

The resistance value of 9 times higher than of a slip ring rotor resistance is connected externally to experience maximum starting torque. The speed control of this motor can be done using two methods which include the following.

How does adding resistance to a motor increase the torque?

In the most direct answer to the question, adding resistance increases the slip for maximum torque (more torque at lower speed) by driving more current into the rotor circuit at lower speed. If rotor resistance were zero (superconductor), the induction motor would operate synchronously, but would be very hard to start!

What does slip mean in an induction motor?

Slip is defined as the difference between the flux speed and the rotor speed. For an induction motor to produce torque, at least some difference should be there between stator field speed and rotor speed. This difference is called ‘slip’.

Why are slip ring induction motor used in elevators?

Because of various advantages like low initial current, high starting torque, and improved power factor, it is used in applications that require high torque, cranes, and elevators. The rotor windings consist of more number of windings, higher induced voltage, and less current compared to the squirrel-cage rotor.