Slip Ring Rotor Resistance

The rotor circuit resistance has significant impact on starting torque the speed at which the breakdown torque occurs and the slip during the normal running operation.

Slip ring rotor resistance.

As rotor winding terminals are not available in squirrel cage induction motor. As the motor accelerates. To overcome this problem the slip ring induction motor comes into the picture. In rotor resistance control method the rotor circuit resistance is varied by connecting a variable external resistance for speed control of induction motor.

Wound rotor motors can be started with low inrush current by inserting high resistance into the rotor circuit. A wound rotor motor also known as slip ring rotor motor is a type of induction motor where the rotor windings are connected through slip rings to external resistance. Starting of slip ring induction motors. The slip ring motor has an external resistance circuit for controlling the speed of the motor.

These motors are usually started with full line voltage applied across its terminals. The slip ring brushes made of graphite are connected to a resistive device such as a rheostat. Also rotor windings are connected through slip rings to external resistance. Whereas in squirrel cage motor it is not possible to add any external circuit because the bar of the motor is permanently slotted at the end of the ring.

Adjusting the resistance allows control of the speed torque characteristic of the motor. Each slip ring is connected to one of the three phases of rotor windings. Rotor resistance control is also one of the methods by which we can control the speed of the induction motor. This method is not applicable to cage rotor induction motor.

The motor which employing the wound rotor is known as a slip ring induction motor or phase. In this scheme the rotor windings are connected through slip rings and brushes with an external variable resistor. 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. The equivalent resistance in the circuit can be adjusted by an electronic control system the slip of the generator can be.

As the slip rings turn with the rotor the brushes maintain constant contact with the rings and transfer the resistance to the rotor windings. Figure 7 17 shows a wound rotor induction generator with rotor resistance control dynamic slip control. However the rotor construction of the slip ring motor is quite interesting. Name one disadvantage of slip ring induction motor and squirrel cage induction motor.

A motor with a wound type rotor is known as a slip ring induction motor. The disadvantages are high copper losses and the low torque. This method is only applicable for slip ring or wound rotor induction motor wrim. As these motors have external resistance connected to its rotor circuit the value of starting current is adjusted or kept minimum by increasing the resistance of the rotor circuit.

What is a slip ring induction motor.