What is the purpose of connecting external resistors to slip ring induction motor?

The slip rings in a wound rotor motor form a secondary, external circuit. Inserting resistance to this circuit allows the motor to produce very high torque at start-up, which is necessary for moving loads with high inertia.

Why do slip rings fail?

Be aware that voltage surges and spikes are the major cause of system slip ring failures. Moog Components Group uses a conservative approach to circuit design, however, it is not uncommon in some power supply systems to see voltage spikes ten or more times the normal operating voltage.

What is the effect of adding an external rotor circuit resistance on maximum torque and starting torque?

This value of resistance is called Critical Resistance. 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 higher resistance of the external cage of the motor?

Outer cage offers high resistance and low reactance. At high frequencies inner cage offers high impedance and outer cage offers low impedance. Hence, current flows through outer cage because it offers lower impedance. 04․

How do I choose a slip ring?

Power requirements In fact, Power is also one of the most important factors to consider when choosing the ring. The voltage drop and current flow across the ring should be considered and given more preference than the power at the load. This is because the power dissipated in the system is affected by the voltage drop.

Which induction motor the external resistance is added to rotor circuit?

slip ring-rotor motor
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. Adjusting the resistance allows control of the speed/torque characteristic of the motor.

How does a motor resistor work?

The resistor is wired into the motor secondary slip rings, where it dissipates torque energy in the form of heat. It also provides “soft starting” as resistance is removed in steps.Initial information needed for sizing your resistor:

How slip ring induction motor works?

The rotor of the slip ring induction motor is connected to the external resistances. When the motor is started the total external resistance get added in the rotor winding resistance and the value of the resistances get gradually decreased with the acceleration of the motor and becomes zero when the motor attains its full rated speed.

How does rotor resistance affect the starting current of a motor?

It has been already discussed in my last article on “Slip Ring Induction Motors..!!,” that increasing the rotor resistance, not only reduces the rotor current, but the stator current too. This implies that the starting current of the motor is reduced when an external resistance is added in the rotor circuit.

What happens if the slip ring is shorted on a motor?

If the slip rings are shorted, a huge current will flow in the stator and the breaker will trip with the overcurrent fault. If the breaker does not trip the electrical power network will experience heavy stress and the motor is likely to get damaged in this situation.