3-phase motors: unbalanced current system

[Freshsurfer]

Hi, I´m working with motor commissioning, my doubt is: when I measure the phase-current of a 3 phase assincronous motor, I got differences in order of 2% between the value of current of one phase and other, when can I say that the system is unbalanced, and which are the risks that I have working on a unbalanced system

Thanks

 

[busbar]

2% unbalance current is probably OK, and may be caused by voltage unbalance or something like stator-winding dissymmetry.

Search this site for a fair amount of discussion on the matter, using keywords “ unbalance “ and “ imbalance “.

 

[jbartos]

Suggestion: Visit

http://www.joliet-equipment.com/operation.htm

for:
If the variation in voltage does not exceed 10% above or below normal, with all phases balanced. Voltage unbalance should not exceed 1%.
However, the 1% voltage unbalance corresponds to the larger current unbalance.
And,

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

http://www.siemp.co.zw/Acrobat Files/module06.PDF

etc. for more info

 

[GGOSS]

Hello Freshsurfer,

See also thread237-70765 "how to calculate kW losses in an unbalance motor". This may provide you with additional useful information.

Regards,
GGOSS