Star or Delta

A VFD output voltage is always quoted PHASE to PHASE. This is because there is no neutral on the output.
Modern VFDs rectify the input voltage to DC and then use solid state switches (MOSFETs or IGBTs) to "chop it up at high frequency into pulses. The timing and width of the pulses are filtered (often just by the motor inductance) into low frequency sinewave outputs. The DC voltage needs to be similar to the peak output voltage. This is easy for 240V in and 240V out, you just rectify and smooth the input. For 240V in 415V out you have to boost the voltage. This can be done as part of the rectification (and power factor correction) circuit or high frequency franspormers on the pulses. Either way it adds components and cost.

Robert G8RPI.

Hi many thanks for your detailed replies, I have gone down the route of using the 240v to 415v VFD/Inverter and running the motor as star. Interestingly the 215 to 415 inverter was of UK Amazon for £70 and is rated at 3HP. I notice the same model has gone up a lot, but for £70 I was prepared for it to break knowing that Amazon would step in and offer a refund.

That said its been working OK on the main 415v two speed motor that runs the std machine (an Aciera F3) on and off for the past two years. The only thing I typically changed in the programme setup is to increase the slow start and decrease the stop speed as this save blowing fuses and of course wired the remote up for control.

Cheers

Barry