Why slip ring induction motor rotor failure occurs?

Answer 1

while running, a slip ring induction motor ,it got tripped and found 2 nos power fuses blown out.on inspection rotor winding IR value zero.ie after releasing the brushes. how it happens?. pl ans

when the motor is starting its an induction motor with a squirrel cage

while its getting up to speed the voltage across the slip rings will be very high

there is a field resister shorting the rings this is removed and replaced with dc

with a make before break field application relay

if the dc is applied before the motor is up to near synchronous speed the stator will need to have very high current to accelerate the mass of the machine

sometimes the controls are magnetic

sometimes a centrifugal switch

sometimes a timer

a compressor will have an unloader to minimise load on the motor before the dc is applied

however this is done

if dc is on the field before you get close to operating speed you will blow fuses

if the "failure" happened while running it could be a momentary power interruption or a momentary load interruption

if the controls didnt see it and restart the motor

you can dissect the fuses and see weather you had a short or an overload

or add a bit more detail about the equipment and incident

Answer 2

No. un uniform air flux will cause imbalance in the shaft