increase in current
Posted 30 October 2005 - 05:39 AM
Why the current increase in the stator while the load increase on the rotor?
Posted 31 October 2005 - 12:35 AM
Have a look at the equivilent circuit of an induction motor and you will see that there are essentially three shunt paths for the current.
- Magnetising current
- Iron loss
- Shaft load
The magnetising current and the Iron loss are essentially constant and independant of load, but the shaft load is drawn as a variable resistance. As the shaft load increases, the value of the shaft load resistance reduces, increasing the current down that leg and increaseing the current into the motor.
From a more practical perspective, as the shaft torque is increased, the slip increases. This results in an increase in the voltage induced in the rotor and thereby an increase in the rotor current.
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