VFD on DC supply?

[DennisCNC]

Nice VFD's take AC volatage and change it to DC and simulate quasi-sinusoidal AC voltage again, will a VFD run off a DC supply voltage?

Thanks

[pastera]

Talk to the manufacturer to find out

There isn't much of a reason why one wouldn't but you would need a high voltage supply in order to run it.

Aaron

[DennisCNC]

So a 240 V 3phase VFD will need around 375v DC?

[Al_The_Man]

Originally Posted by DennisCNC will a VFD run off a DC supply voltage?

Why would you want to if it already has a built in power supply, it should however be possible, as long as the VFD does not use a low voltage transformer for the low level DC logic. And the DC supply has sufficient capacity.
Al.

[Geof]

Originally Posted by DennisCNC ... will a VFD run off a DC supply voltage? Thanks

Yes.

In Vancouver, B.C. there is an electrically driven elevated transit system called Skytrain. It runs on steel rails and is driven by variable frequency three phase linear motors beneath the cars that act on a reaction plate between the tracks. The electrical supply is obtained from power rails like many electric trains and is 650Volts DC so the VFDs that drive the linear motors are running on a DC supply.

Actually a great many subway systems uses variable frequency drives that run from a DC supply and this system is also used for electric trolley buses.

These are much bigger and higher voltage and power systems than you are thinking about but they do demonstrate it is feasible.

You would probably need a low power inverter running off your DC supply to provide the control voltage for the VFD while the DC supply would take the place of the incoming rectifier circuit and capacitor bank. There would be a lot of cutting and changing needed to a standard VFD.

I think a system like this would be an excellent way to average a large load that is used on a low duty cycle so it could be used on a low amperage supply. A battery bank could be charged constantly from the low capacity supply and the VFD would discharge the batteries during the time that its demand exceeded the charging supply. The size of the battery bank would be dictated by the duty cycle of the high demand load and how much voltage droop was acceptable at the DC input to the VFD.

[DennisCNC]

^^ Good info about the Skytrain.
A idea hit me so I wanted to see if VFD's like DC voltage and it seems they do. This might be far future project.

[sch]

In principle a VFD would work off DC, assuming a bridge rectifier as the input circuit and no transformers, which judging from their weight is unlikely but can't rule out a control voltage transformer in there somewhere so a case removal and eyeball would be a good idea in advance. The bridge would rout the +/- input to the right place regardless of which lead you use. The proper voltage would require some thought and experimentation but I don't think a 220vac input VFD would need more than 300 VDC in at an appropriate amperage, and might get by with less, though certainly not less than 220vdc.
As suggested a knowledge of how the control/low voltage circuitry in the VFD gets its power would be critical to this application. The high power part of the circuit would not in principal require any cutting/rewiring as the AC-DC conversion (rectifier bridge+capacitor) will just pass the DC right on through,
the bridge handling polarity conversion.