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Rams
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Join Date: Apr 2009
Posts: 5

Acceptable Voltage Unbalance in Transformer Secondary; While Primary Constant

05/23/2010 10:39 AM

Clarify how much voltage unbalanceness shall be allowed in a trnsformer secondary while the primary voltage remains constant? is there an IEC standard for this...?

Same way how much shall be allowed for motors terminal?
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msamad
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Join Date: Feb 2009
Location: Houston, USA
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#1

Re: acceptable Voltage unbalanceness in transformer secondary(While primary constant

05/23/2010 11:02 AM

If you have 3 phase motor, maximum 1% voltage unbalance is allowed in NEMA. 1% of voltage unbalance can create 6-10% current unbalance for the motor. If the voltage unbalance is more than 1%, the motor has to be de-rated.

Somebody else can shade light on IEC regulation.

See

http://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/voltage_unbalance_rev2.pdf

http://progress-energy.com/custservice/carcig/resourcectr/presentations/MotorProtection_VoltageUnbalance.pdf

http://www.patchn.com/index.php?option=com_content&task=view&id=41&Itemid=74

http://www.elongo.com/pdfs/voltages.PDF

- MS

__________________
 "All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)
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Rams
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Posts: 5
#2
In reply to #1

Re: acceptable Voltage unbalanceness in transformer secondary(While primary constant

05/24/2010 11:12 AM

Many thanks for your reply Mr.MSAMAD.....

Rams
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