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Problem with dual speed motor


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#1 glenmar

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Posted 09 July 2005 - 04:18 PM

Gentlemen,

I have encountered a problem with a motor, double speed, two windings, wye / wye connetion, single voltage. The motor draws high current when ran at high speed connection, but normal at low speed connection. Insulation test is good, it has a balance winding resistance, the driven load is not obstructed.
And why is it that there is a need to connect/bridge the leads of the low speed winding when at high speed mode?

Regards to all,

Glenmar

#2 marke

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Posted 09 July 2005 - 09:17 PM

Hello glenmar
Welcome to the forum.

It is normal for the current on high speed to be higher than on low speed. The power rating of the motor will change with the speed so even open shaft, there could be a greater than 2 or 3 to one change in current.
Under load, there wil definelty be a change in current. For example, pumps and fans have a square law curve of load, so if you doulbe the speed the load will be four times.
Perhaps you can give more detail, compare the currents with the nameplate ratings. It is difficult to answer fully without full data.
Common dual speed configuration is delta/double star Low speed is delta connected and highspeed , the winding is effectively two stars in parallel.

Best regards,

#3 glenmar

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Posted 09 July 2005 - 09:53 PM

Hi Marke,

Thanks for the reply,
The said motor draws current 4 times of its nameplate rating.
This is the first time i encountered such motor connection which is two winding wye / wye configuration, double speed.
I have searched the internet for any document relating to the said motor connection but found nothing.

I suspect that there is a coil to coil or turn to turn short in motor windigs.

Regards,

Glenmar

#4 marke

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Posted 10 July 2005 - 02:41 AM

Hi Glenmar

Is this a amchine and controller that has been operating correctly up till now and just failed, or is it a new installation?
Do you have a circuit of how it is wired up?

Best regards,
Mark.

#5 Guest__*

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Posted 14 July 2005 - 10:55 AM

Hi marke,

The said motor already ran for 2 years now. and it just failed recently. i'l provide the circuit diagram later.

Thanks and regards,

glenmar




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