Hi All,
I have a machine with a large 600W AC motor which contains its own variable frequency drive (VFD) which allows the motor to run at a range of speeds. It has a 3-phase input but I need to run it from single-phase. It seems to me that I can do this very simply and without an external converter. The VFD circuit rectifies the incoming line AC to DC and then has a digitally controlled variable frequency driver circuit which runs the motor from that. i.e. as simply depicted
here.
The AC input goes into a PCB which is a set of filters (X caps, MOVs and a choke) which then go into a panel mounted bridge rectifier, from there into the main PCB (see pics). These particular models are usually sold as single-phase; mine is unusual. It is rated “200-440V AC 3 Phase”, allowing it to run in US or Europe. I’m in UK so 240V single phase (440V 3-phase if I had it). I suspect that the main PCB is the same between the single phase input and 3-phase input units, with the difference being the line filter and the bridge rectifier. I attach a picture of the filter PCB, the bridge and the main VFD PCB.
So, I think I can simply disconnect one of the 3 line inputs (or maybe tie two of the 3 together) and run it on single phase 240V AC. My thinking is that the bridge rectifier is rated for the higher current that would be needed for 3-phase in the USA and it will just rectify the single phase “as normal”.
I wonder:
- Is that correct?
- If so, does it matter if I leave the spare live input floating or connect two of the 3 together?
- am I missing anything?
Thanks!