What is the effect of rotor resistance on the maximum torque?

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.

What are the effects of changing rotor resistance?

Thus by changing rotor resistance the starting torque can be controlled. If now resistance is further added to rotor to get resistance as R2′ and so on, it can be seen that Tm remains same but slip at which it occurs increases to sm’ and so on. Similarly starting torque also increases to T’st and so on.

What is the effect of increase in rotor resistance on the maximum torque of three phase IM?

The maximum torque is inversely proportional to rotor reactance. The maximum torque is independent of rotor resistance. The slip at which maximum torque occur depends upon rotor resistance, R2. So, by varying the rotor resistance, maximum torque can be obtained at any required slip.

Does rotor resistance affect the maximum torque developed in the induction motor?

By varying the resistance in the rotor circuit, maximum torque can be obtained at any desired slip or speed. It depends upon the rotor resistance at the slip (sM = R2/X20).

What is the effect of rotor resistance on maximum torque and slip corresponding to maximum torque explain with neat diagram?

The maximum torque is independent of the rotor resistance. But the exact location of the maximum torque Ʈmax is dependent on it. The greater, the value of the R2, the greater is the value of the slip at which maximum torque occurs. As the rotor resistance increases, the pullout speed of the motor decreases.

What is the effect of increasing the rotor resistance on starting current and torque?

The starting torque of an induction motor increases with increasing rotor resistance. However, we know that, with increasing rotor resistance, rotor current will reduce, and hence rotor flux will reduce. Starting torque is the torque produced by induction motor when it is started.

What effect does the slip ring starting resistance have on the starting torque and the starting current?

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.

What is the effect of change in rotor resistance on torque slip characteristics?

When slip at starting becomes equal to slip corresponding to maximum torque. Thus by adding external resistance to rotor till it becomes equal to, the maximum torque can be achieved at start.

What is the effect of change in rotor resistance on the speed of induction motor?

This equation shows that for a constant torque, the slip is directly proportional to the 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.

What is the effect of adding resistance in the rotor circuit on the starting current and the starting torque in a three phase slip ring induction motor?

In the case of slip ring motors, the rotor resistance is increased by the addition of external resistance. This external resistance makes the rotor circuit current low. Hence by increasing the rotor resistance, we can improve the starting torque of the wound rotor induction motor (W.R.I.M.).

What are the effect of variation of rotor resistance on speed of rotor?

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.

What are the effect of variable rotor resistance on torque speed curve?

Rotor resistance can be increased upto that when Starting torque becomes equal to Maximum value of torque, because after that Starting torque gets reduced. This value of resistance is called Critical Resistance. When slip at starting becomes equal to slip corresponding to maximum torque.

How does rotor resistance affect torque and slip?

So, in answer to your question, increasing rotor resistance would increase the slip at maximum torque; it would also lower the maximum torque. In other words, the maximum torque and the RPM where the maximum torque occurs will both decrease. Decreasing the rotor resistance would have the opposite effect.

Why induced torque is zero in synchronous motor?

3) If the rotor speed is equal to the synchronous speed, induced torque is zero. Torque slip characteristics is depends on the rotor resistance. As the rotor resistance varies, the value of maximum torque remains as it is. It means that, the value of maximum torque is independent from the rotor resistance.

What is torque slip characteristics?

Hence, torque slip characteristic is an approximately straight line as shown in the above figure. 3) If slip increases with the increase in load, the torque reaches the maximum value. At this time, slip is equal to the rotor resistance and rotor reactance. The maximum torque is also known as the pull-out torque or break down torque.

How do you increase the torque of a rotor?

Maximum torque occurs when the slip = Rotor Resistance / Rotor Reactance. This is when the power factor of the rotor circuit (just the rotor part Adding resistance does not increase the peak torque. It increases the torque at higher slip (earlier in starting).