How can we increase the starting torque of an induction motor?

How can we increase the starting torque of an induction motor?

There are three ways to improve the starting torque of Single phase induction Motor

1. Internal Rotor Resistance. The across the line starting torque at low speed can be increased by increasing the rotor resistance.
2. External Rotor Resistance.
3. Variable Voltage/Frequency.

What happens to the starting torque of a wound rotor motor when you increase the resistance in series with the rotor windings?

Wound rotor motors are also referred to as “slip ring motors.” During starting, this resistance is placed in series with the rotor windings. This added resistance causes the rotor current to run more in phase with the stator current, which increases the torque that is developed.

How do you control the output of a wound rotor motor?

The speed of the wound rotor or slip ring induction motor can be controlled by varying the resistance in the rotor circuit. This method is applicable to slip ring induction motor only. When the motor is running and if the full resistance is connected in the rotor circuit the speed of the motor decreases.

How do you start a wound rotor motor?

Wound-rotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit; as the motor accelerates, the resistance can be decreased.

Does higher voltage mean more torque?

The higher the voltage, the higher the torque. The voltage rating of a DC motor indicates the most efficient voltage while running. Operating torque is the amount of torque the motor was designed to give and stall torque is the amount of torque produced when power is applied from stall speed.

How do you increase engine torque?

To increase the torque that a bit harder. All you can do, electrically (as you can do it mechanically via gears), is to reduce the source impedance to maximise the current that can be delivered for a given stator impedance. Rewind it with more turns of thinner wire.

What is the difference between rotor speed and synchronous speed?

Induction motor with squirrel cage rotor has two different speeds. The synchronous speed refers to the stator rotating magnetic field, which depends on the number of poles and frequency. The other speed is the rotor’s. The rotor speed will be always slower than the stator speed, we call it slip.

What is the drawback of rotor Rheostatic speed control method?

The major disadvantage of the rotor resistance control method is that the efficiency is low because of the additional losses present in the resistors connected within the rotor circuit. The efficiency is greatly reduced at low speeds because of the higher value of the slip.

Why will the rotor of a wound rotor motor not turn if the rotor circuit is left open with no resistance connected to it?

If the circuit is left open, the current will not flow in the rotor, this leads to the absence of the magnetic field in the rotor. Therefore, there will be no torque between the rotor and the field. Hence, the motor will not start.

How do you test a wound rotor motor?

If you run a wound rotor motor with brushes that are barely contacting the slip rings, the motor may draw high current. An optional test is to connect the stator leads together, and run the motor by energizing the rotor leads at the rated secondary voltage.

What is standstill rotor EMF?

When rotor is stationary i.e. s = 1, the frequency of rotor e.m.f. is the same as that of the stator supply frequency. The value of e.m.f. induced in the rotor at standstill is maximum because the relative speed between the rotor and the revolving stator flux is maximum.

Is current proportional to torque?

Electrical motor torque is proportional to the product of magnetic flux and the armature current. Motor current varies in relation to the amount of load torque applied. When a motor is running in steady state, the armature current is constant, and the electrical torque is equal and opposite of the mechanical torque.