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 Post subject: Motor Capacitors/Models of Capacitance
PostPosted: Tue Oct 25, 2011 9:02 am 

Joined: Tue Sep 20, 2011 6:49 am
Posts: 5
Location: Earth
I am doing a smaller study at a site that has some motors that have capacitors attached to the lugs of the motor.

I don't know it if is necessary to include them. I'm not sure how the system models them, and it is not like they are a capacitor bank that are storing massive amounts of energy. They are 37.5KVAR and smaller, feed from a 480V MCC.

I'm sure there effect would be minimal, however, it now leads me to question how does the model deal with Capacitance? Does it act as dump or contributor of energy in case of a fault? Can I set it's run state/fault energy/ext?

I imagine that a capacitor bank of any kind would be like a battery dumping directly into the fault, and would greatly effect the fault current of any study. However, if a capacitor is being used in conjunction with a motor would absorb energy that the motor is contributing or add energy to the system?

Should I make another scenario and test for both?

I am using SKM to model Arc Flash.

Thanks!


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PostPosted: Wed Oct 26, 2011 3:31 am 
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Joined: Sat Jun 07, 2008 5:11 pm
Posts: 143
Location: Connecticut
Sounds like power factor correction capacitors which are used on larger 3 phase motors. They typically have very low capacitance values (uf) don't contribute to fault current.


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