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Motor size.


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#1 chaterpilar

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Posted 24 November 2005 - 02:57 PM

I have two questions....

1) We received a 50 Hz 55 kw 380 volts motor which looks much smaller than what you would expect a 55kw motor to be. The Frame size in terms of width and breadth of base are matching with Frame 250..
How do you establish a motor kw ( if in doubt) as to what size it is.... ?

2) What are the effects on a 50 Hz motor when run on 60 hz supply and 60Hz motor running on 50 Hz supply...?

thanks and regards,

chaterpilar


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#2 marke

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Posted 24 November 2005 - 06:01 PM

Hello chaterpilar

I am not aware of any way that you can dimensionally determine the rating of an induction motor.
If you look at data sheets, you will see that it is common to have several different ratings within one frame size.
At the end of the day, you either trust the ratings aplied by the manufacturer or you do not. If you don't, use a manufacturer that you do trust.

Best regards,

#3 niallnz

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Posted 24 November 2005 - 11:03 PM

Hello Chaterpillar,

I've looked through my motor catalog and can confirm that a 380V 55kW 50Hz 2 pole or 4 pole is a 250 frame size. 55kW needs a 280 frame for 6 or 8 poles.

Cheers Niallnz

#4 niallnz

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Posted 24 November 2005 - 11:04 PM

Hello Chaterpillar,

I've looked through my motor catalog and can confirm that a 380V 55kW 50Hz 2 pole or 4 pole is a 250 frame size. 55kW needs a 280 frame for 6 or 8 poles.

Cheers Niallnz

#5 chaterpilar

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Posted 25 November 2005 - 03:01 PM

Thanks marke and Niall,

I was thinking whether a no load current test can give an idea about the motor..normally noload currents of 2 pole motors are 20 % of FLC.(110 amps) for 55kw motor.

So, if i run this motor on Noload i expect it to be about 22 amps...anything drastically less than that would mean lower size motor delivered as 55kw.

Both of you have not replied to the second question....
50 hz/60hz motors..

chaterpilar

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#6 marke

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Posted 25 November 2005 - 07:25 PM

Hello chaterpilar

The open shaft current of a motor varies considerably between motors and generally falls in the range of 20% to 40% of the rated current of the motor. Small motors and submersible pumps can have magnetising currents in excess of 60% FLC, so the open shaft current does not give any reliable indication of motor size.

For your second question, see http://www.lmphotoni..._qanda.php?id=9 and http://www.lmphotoni...qanda.php?id=12

Please remember that this is a voluntary frum. Do not expect answers to everything, or immediate responses. We do not endeavour to provide a free consulting service!!

Best regards,

#7 chaterpilar

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Posted 26 November 2005 - 02:47 PM

Dear Marke,

Sorry for the overenthusiasm....

will keep that in mind..

The links were very useful..

Thanks again..

I am sure the paid service will not be as helpful as your forum..


Best regards,


Chaterpilar

" If you tell the truth, you don't have to remember your lies ..."




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