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Speed Reduction in Induction motor

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#1 rksharma76


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Posted 16 March 2006 - 10:56 AM

Case: One of our FIN-FAN motor is running with 1360 RPM against the rated RPM of 1450. Infact all other motors are running on their rated RPM in same fin fan bank. what may be the probable reasons for such a speed reduction in motor (Motor do not have any VFD). Can the change of connection from star to delta will help?


Rakesh Sharma

#2 chaterpilar



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Posted 16 March 2006 - 12:52 PM


That motor may have higher slip. Is the current drawn by this motor higher than its neighbour?

Interchange the two motors and see the difference.

Good Luck !!


#3 ssands


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Posted 16 March 2006 - 02:41 PM

chk motor voltage/current/freq. rating.
if possible chk rotor ,also verify stator rotor airgap.

#4 marke


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Posted 16 March 2006 - 05:57 PM

Hello rksharma76
Welcome to the forum.

I would ensure that the connection is the same as the other motors. If the slower motor is connected in star and the others are in delta, this would certainly create an increase in slip as you describe, but I would expect that if the motors are close to fully loaded in delta, the slip in star would be much greater and the motor would fail reasonably quickly.

The usual cause of increased slip for eaual shaft load, is a rotor problem. If the motor is connected correctly, and drawing a very similar current, it would suggest to me that there is an issue with the rotor. If the current is swinging very noticably compared to the other motors, it would indicate a damaged or open circuit rotor bar.

Best regards,

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