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Motor Failure


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Dear All,


II am a new member in this forum. I am a Senior Technician in a manufacturing industry for 10 years.

I am facing a problem in a blower motor on one machine. Information typed on its name plate is as 18.5Kw, 380V, 35A, 50Hz and 4 poles. The motor draws 32A on no load condition. When we run the motor on load and blower runs, the motor draws 34-38A. This motor has re-winded once a time but still runs in same condition.

Its no load current must not greater than 35x.5 = 17.5A (max). I am confused that what the problem in motor is, as it is re-winded.

Can any body explain?

Thanks in advance.



"Don't assume any thing, always check/ask and clear yourself".

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Hello AB2005


Welcome to the forum.


Many years ago, I had a similar problem with a pump motor. This motor was rewound twice and gave the same results. The third time, the rewinder checked the design rather than duplicating it and we discoverd that the motor was would for 60Hz. but the nameplate was marked 50Hz. The third rewind was designed for a 50Hz motor and all was OK.


A high magnetising current (greater than 0.5 x rated current is usually because the motor is operating above it's design voltage or below it's design frequency.

You could connect a VFD and try changing the voltage and/or frequency and that way you can determine what the optimum settings are, then you can get it rewound properly!!


If the motor has been damaged, there can be a problem with the laminations that can cause a high current.


Best regards,

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