Voltage drop calcs. for motor feeders w/ remote VFD

[steveve1]

Hello All and Merry Christmas from chilly Arizona, I'm wondering how having a VFD mounted a distance away from the motor affects voltage drop calculations. For example: A 10hp motor @ 480v, 100' feeder length. At nominal voltage I assume a load of 14a. VD calcs indicate a drop of 4.8v with #12cu conductors. Will the conductor size be adequate through the range of the applied voltage to the motor from the VFD? I have an installation with several VFD controlled motors, varying distances and HP. Is there a general "rule of thumb" or will standard VD calcs apply regardless of the VFD control?

Thanks in advance....and Happy Holidays!

 

[Paul B]

I've never taken into consideration that it was powered by a VFD, just distance wire size and amperage.

 

[jdcpe17]

shouldnt affect it. vfd is changing the frequency of the alternating current.

 

[bob]

You calcullations are based on 60 cycles. I suspect the output from the drive is much higher that that.
Did you actually measure the VD? Cable impedance at the higher frequency will increase.

 

[jojo]

Others use one size higher of its conductor ampacity with VFD control to compensate for harmonics.