Input voltage of VFD

[ldtOLER1112]

Is there anyway to change the input voltage on a VFD. I've got 120/208 and the VFD is 400 to 460 input

 

[winnie]

Not practically.

You can of course use a step-up transformer to convert the 208V to 480V and supply that to the VFD.

In theory the internal power components (IGBTs, capacitors, rectifier, etc) will work just fine at the lower voltage, so if you were to modify the 'control electronics' power supply to correctly operate at the lower voltage, and adjusted the various error thresholds to operate with the lower voltage, then you could use the modified VFD at the lower voltage. But in addition to being a potentially difficult modification, the power rating of the VFD would drop by the voltage ratio, so you would have thrown away most of the VFD capacity.

Jon

 

[petersonra]

Is there anyway to change the input voltage on a VFD. I've got 120/208 and the VFD is 400 to 460 input

Your best bet is to either replace the VFD or get a step up transformer. These days just getting any VFD is a chore so your best bet is probably a step up transformer. I would suggest a 3 phase 208 delta primary to 3 phase 480 wye secondary.

 

[garbo]

Your best bet is to either replace the VFD or get a step up transformer. These days just getting any VFD is a chore so your best bet is probably a step up transformer. I would suggest a 3 phase 208 delta primary to 3 phase 480 wye secondary.

The few times we had to change either 208 or 240 volts to 480 volts never used a Wye on the secondary if it was feeding a three phase drive or motor that only required 3 wires.

 

[don_resqcapt19]

The few times we had to change either 208 or 240 volts to 480 volts never used a Wye on the secondary if it was feeding a three phase drive or motor that only required 3 wires.

If you don't use a wye with the center grounded, you will have to make the 480 corner grounded or install ground detectors.

 

[Jraef]

There are two basic design philosophies when it comes to the source of internal control power for VFDs; tap off of the line side and have an AC/DC power supply, or tap off of the DC bus with a DC/DC power supply. In the earlier days, most mfrs went with the AC power supply option because it was cheaper and by using an auto-ranging SMPS design, meant that each voltage rating had the same power supply board. Eventually though almost every mfr (that I know of) migrated to using a DC/DC power supply tapped from the DC bus, because it allowed the VFD to be used on single phase sources without having to worry about which line side terminals to use, and (importantly) because DC/DC power supply components became cheaper and small enough to put on the same main board, so no separate power supply board. But it also meant that they were now different for the different voltage classes. Generally though, the DC/DC power supplies can tolerate a voltage range down to around 70-65% of the rated Line Voltage, so a 480V rated drive can be used at 380V - 10% without any issues, the same would hold true for a 240V rated drive being good for 200V - 10% as well. But 480V from a 240V source is unlikely to work.