What will happen if supply to three phase motor is given
wiyhout inerting rotor in it?How much current it will draw?
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Answer Posted / xyz
Normally, when a motor is switched on, it takes a heavy
current (6 to 7 times the rated current of the motor).This
is because there is no back emf. Then the rotor starts
rotating and picks up speed. As the speed increases and
reaches the rated speed, the back emf increases and the
current decreases and reaches the normal value.
When a motor is switched on without the rotor,the situation
is similar to the one that exists at starting time. There
is no back emf and hence the current will be heavy.Since
there is no rotor, there is no question of back emf. Hence,
if the protection does not trip the supply, the winding
will burn.
You can use this as a project for your science exhibition.
You put the motor (without the rotor) in such a way that
the axis is vertical.Now the vacant space created by the
removal of the rotor is like a cylinder. Close the bottom
part with a plate. Now you can put coins in that
cylinder.Apply a small voltage to the motor winding to
create the revolving magnetic field.The coins will start
moving in the direction of the revolving magnetic field.
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