Quote Originally Posted by m_c View Post
I know voltage increasing VFDs do exist, but I can't see anything on either the Huanyang or Ecogoo sites/manuals about those VFDs being able to boost voltages.

You can run 380V three phase motors from single phase using 230V single phase, however once you reach a certain frequency (roughly 2/3 of max rated frequency IIRC), the power available becomes voltage limited. Above that speed you can't get full power, as the voltage isn't high enough to overcome the back emf and drive the required current through the windings, so the available torque drops of as speed increases.
Inverters Direct (aka Drives Direct) supply 230 to 380V VFDs. I did look into them and they are a commercial make (I did have the make/model, but can't find it) with lots of Drives Direct stickers on them. The non-rebadged inverters are available cheaper, but I suspect Drives Direct are doing some internal modifications to boost the input voltage.

The easiest way to achieve it, would be a 250 to 380V step up transformer, big bridge rectifier, and bank of suitable capacitors, and feed the resulting 540VDC direct into the inverters DC bus. That way you bypass the VFDs own rectifier circuits (you could feed the 380V single phase directly in, however you risk overloading the VFDs internal rectifier circuit, and overheating the internal smoothing capacitors due to the increased ripple from only having a single phase supply).
The other option, which is what I suspect Drives Direct are doing, is using a suitable oscillator circuit and inductors to do the boosting, as it would result in a far more compact system.

I'd like to get my hands on a Drives Direct VFD to see just exactly what they are doing, but I'm not willing to pay their prices, and I don't think anybody who has bought one, would be willing to let me dismantle it to have a look.
No need- its all done in the dual stage vfds i have! perfect 380v. under £400 so why mess about. i have them running hsd spindles and a big hydrovane in my workshop for over 2 years now. i test all spindles i sell using the newer ecogoo 9100 :-)
its the only one that can output to the frequencies i require - standard up to 650 hz and special order to 800hz