VFD as DC power supply

goghie · Sep 11, 2021

I need small power supply that has very small ripple and 250VDC for my workshop. I came to idea to use DC bus from VFD that has 3x230VAC output as it seems cheapest solution. Any thoughts or suggestions?

BryanG · Sep 11, 2021

AC voltage isn't as advertised

. When you read an AC voltage it is the RMS value that you are given, but the peak voltage is 1.414 times the RMS voltage. So for a 230V supply the peak value is 325.2 Volts. The DC Bus Voltage will be somewhere between the RMS voltage and the Peak Voltage depending on the load on the VFD.

https://testguy.net/content/270-Peak-vs-Average-vs-RMS-Voltage

g.mccormick · Sep 11, 2021

Instead of a vfd, why not use a dc drive? Ive used abb dcs drives as variable power supplies to feed eddy current dynos before

goghie · Sep 11, 2021

@BryanG
I know the value of DC bus, but it is easy to set-up to 250VDC.
@g.mccormick
I intended to use VFD as I have one good Mitsubishi on stock

AustralIan · Sep 12, 2021

goghie said:
@BryanG
I know the value of DC bus, but it is easy to set-up to 250VDC.

How do you control this?

BryanG · Sep 12, 2021

I have to admit that the last time I put much effort in to studying VFD circuits was in college, I think Eddison and Westinghouse were still arguing about whether AC or DC was better. If your VFD has a way to control the DC Bus voltage then you have your solution. The ABB drives that I commonly use only have DC Bus Voltage as an output value.

goghie · Sep 12, 2021

@Australlan
I will control it with High Power Wirewound Precision Rheostat, as it is for testing equipment that has very small load but it needs to have the output of supply as smooth as possible.

VFD as DC power supply

goghie

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