Why is the no load current drawn by 3 phase induction motor so high?
The most common causes of high no-load current after a motor is rewound are incorrect winding data and stator core damage. Incorrect winding data that increases the magnetic flux levels as compared with design levels will result in increased no-load current.
Why magnetizing current in induction motor is higher than transformer?
The magnetic circuit of the induction motor has an air gap and hence higher reluctance as compared to a transformer magnetic circuit having no air gap. In order to set up magnetic flux inside the air gap of induction motor, large magnetizing current is required.
Why does induction motor has high starting current?
This high current in the rotor will create its own magnetic field which opposes the main stator magnetic field, this weakens the stator magnetic field so the back EMF in the stator will drop and the supply voltage will be much higher than the stator back EMF and so the supply current increases to a high value.
Why induction motor starting current is very high?
At start, the reactance of the rotor is high because the slip of the motor is equal to unity. The value of Rr/s increase as the slip gets decrease. When the induction motor is started the rotor reactance is more than the rotor resistance and because of the large Xr/Rr ratio the motor takes large inductive current.
What is the no load current of 3 phase induction motor?
The three-phase induction motor carries a three-phase winding on its stator. … The no-load current of the motor is sometimes as high as 30 % to 40 % of the full-load value.
What is no load current of induction motor?
The current drawn by the induction motor when it is not coupled to the driven equipment is called no-load current of the motor. The equivalent circuit of an induction motor at no load is as given below. The no-load current produces the magnetic field in the motor. There are two parts of no-load current.
What is no load current?
The no-load current is the current required just to turn the motor shaft with nothing connected. It is the current required to overcome the bearing and brush friction plus the aerodynamic drag caused by the rotor moving in the air and moving air through the motor for cooling purposes.
Why the PF of an induction motor is less than 0.5 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.
What are the causes of low power factor of 3 phase induction motor?
Variations in power loading – When the system is loaded lightly, the voltage increases and the current drawn by the machines also increases. This results in a low power factor. A condition known as 3 phase power imbalance occurs, due to improper wiring or electrical accidents. This results in low power factor too.