Unbalance Resistance

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Gigabolt Associate Join Date: Jan 2009 Posts: 26	Unbalance Resistance 01/19/2009 11:09 AM
	Hi, I have a motor drive (inverter) connected to 26Kw motor via a collector. I have recently found that the resistance at the output cable of the inverter to the motor (measurement carried out by disconnecting the output cable from inverter) was very much different from phase to phase ie: 0.4 ohm red to yellow, 12 ohm yellow to blue and 7 ohm blue to red. I have double check at the motor by carry out measurement only at the motor terminal and the value was good (0.4ohm, 0.4ohm,0.4ohm phase to phase) I have later found carbon accumulated at the collector's carbon brush. I have a question here: what is the consequence to the above resistance differences, will it kills the inverter or damage the motor? or it is just fine to operate it as the collector was suppose to be a maintenance free type.
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fisher Active Contributor Join Date: Jan 2009 Location: mid atlantic usa Posts: 11	#1 Re: Unbalance Resistance 01/19/2009 11:49 AM
	Gigabolt, please provide a description of the "collector". The line to line voltage drop ocurring due to the resistance of the carbon contamination is likely detrimental due to the fact that you are now dealing with series/ parallel combinations that will divide both applied voltage and drawn current. __________________ God is good all the time, all the time God is good.
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Gigabolt Associate Join Date: Jan 2009 Posts: 26	#4 In reply to #1 Re: Unbalance Resistance 01/20/2009 11:37 AM
	A brief description of the collector: This collector is a copper ring built on a rotating arm. it is connected via maintenance free carbon brush from motor drive and to the motor, each ring comprises of 2 set of carbon brush, one for the drive and the other for motor. carbon contamination was found on the ring and under the brush. besides having the potential to cause motor damage, will it cause the drive to fail? because lately i have a numbers of drive failure. i wonder whether it is cause by the above?
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V.I.Abraham Guru Join Date: May 2007 Location: Pune , India Posts: 875 Good Answers: 42	#2 Re: Unbalance Resistance 01/20/2009 8:21 AM
	Hi Gigabolt, It can damage your motor. Better clean the brushes regularly to avoid unbalance voltage for motor.
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capblanc Guru Join Date: Jul 2008 Location: Mallorca, Spain Posts: 567 Good Answers: 15	#3 Re: Unbalance Resistance 01/20/2009 10:57 AM
	Hi all, the symptoms descibe a high resistance cable, nothing more! regards Chas __________________ En la casa del herrero, cuchillos de palo!
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capblanc (1); fisher (1); Gigabolt (1); V.I.Abraham (1)

You might be interested in: Motor Controllers, AC Motor Drives, Motor Test Equipment

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