Why should induction motors not allow to run under no load or light load conditions?

At no load, an induction motor draws a large magnetizing current and a small active component to meet the no-load losses. Therefore, the induction motor takes a high no-load current lagging the applied voltage by a large angle. Hence the power factor of an induction motor on no load is low.

What happen when induction motor run on no load?

As the motor is running at no load, the total input power is equal to the constant iron loss, friction, and windage losses of the motor. Since the power factor of the induction motor under no-load condition is generally less than 0.5, thus the Wattmeter reading of one of the Wattmeter will show a negative reading.

Under what condition can an induction machine be operated as a generator?

synchronous speed
The Induction Motor becomes a generator when it is connected to an electrical power system and then driven above its synchronous speed by some prime mover.

Can an induction motor work as a generator?

Induction generators operate by mechanically turning their rotors faster than synchronous speed. A regular AC induction motor usually can be used as a generator, without any internal modifications. An induction generator usually draws its excitation power from an electrical grid.

What is the purpose of no load test?

The open-circuit test, or no-load test, is one of the methods used in electrical engineering to determine the no-load impedance in the excitation branch of a transformer. The no load is represented by the open circuit, which is represented on the right side of the figure as the “hole” or incomplete part of the circuit.

What is the purpose of no load and blocked rotor test?

1. To obtain the variation of no load power and current and blocked rotor power and current with changes in the applied voltage to the stator. 2. To determine the equivalent circuit parameters of an induction motor.

When an induction motor works as an induction generator?

An Induction motor will operate as an induction generator when the speed of the prime mover is at synchronous speed but not above it . As a basic principle of generator a prime mover is be coupled with an induction motor and run at synchronous speed.

Why does the power factor of an induction motor at the no load condition have lower value than the power factor at the full load condition?

As the Induction Motor is loaded, the load component of current increases from its no load value. The increment of load component of current from its no load value is responsible for supplying the load torque. Thus as we increase the load Ɵ1 decreases which in turn means an improvement in power factor.

How does an induction motor become a generator?

The Induction Motor becomes a generator when it is connected to an electrical power system and then driven above its synchronous speed by some prime mover. The prime mover may be a turbine, an engine, a windmill, or anything that is capable of supplying the torque and speed needed to drive the motor into the over-speed condition.

What happens when an induction motor is overhauled?

If the induction motor is sped up by an overhauling load, the difference can fall to 0 and thus no current in the rotor and thus no magnetic field in the rotor. Torque can be in either direction depending upon the relative direction of rotation between the rotating magnetic field of the stator and the induced magnetic field of the rotor.

What makes a squirrel cage induction motor a good generator?

The squirrel cage Induction Motor makes an excellent generator when it is driven above its synchronous speed.

How do induction motors produce torque?

Induction motors produce torque based on the DIFFERENCE between the rotor speed and synchronous speed. The applied line voltage produces a rotating magnetic field whose lines of flux are cut by the squirrel cage rotor windings. When those windings cut flux lines, a current is induced that produces a rotating magnetic field.