capacitors

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mickeyrench

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edison, n.j.
We have a vfd that drops out on under voltage according to the vault indicator on the vfd when ever this other motor seems to start up in a other mcc area.
we can't find any low voltage. We were told we can install capacitors to the vfd to keep it from droping out on undervoltage. I like to know how to size up capacitors for this situation and would they be install on line or load side of vfd?
 
Many questions... One possible answer

Many questions... One possible answer

Are both feed from the same XMFR via common SG to separate MCC's?
Is load close or maxed out for the XMFR if common for both motors.

Is this a new issue?
Has it happened often, or could seasonal heating adding to loading.

How big are both motors in question?
Type of Drive would be nice also.

Normally a drive can ride through brief dips, this may be an adjustable value. Depending on the type of VFD the parameter can be turned on or off, and possibly have additional adjustment. If load is not a issue this is where I might look next.
 
081210-1926 EST

mickeyrench:

I believe the capacitors being referred to are the DC bus capacitors. Increasing these would up the energy storage and allow you to operate thru larger or longer dips in supply voltage.

But answer some of the above questions first.

.
 
mickeyrench said:
We have a vfd that drops out on under voltage according to the vault indicator on the vfd when ever this other motor seems to start up in a other mcc area.
we can't find any low voltage. We were told we can install capacitors to the vfd to keep it from droping out on undervoltage. I like to know how to size up capacitors for this situation and would they be install on line or load side of vfd?
Click to expand...

this issue just came up about a month ago and the people incharge blame this onthe other motor but today i shut down the vfd completely and we started this other motor, when finished we shut the motor off then turn the 3 phase 480 on and the vfd came up with the undervolt vault again and then in time it resets itself. it is controled with a external signal i think 4-20ma from a water level . thanks
 
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