On Thu, Jan 7, 2016, at 05:31 PM, andy pugh wrote: > On 7 January 2016 at 22:10, John Kasunich <jmkasun...@fastmail.fm> wrote: > > > This is rarely ever done in industry because industry doesn't want > > to pay for the extra iron, copper, silicon, and capacitors needed > > to build a 10HP motor and VFD when they're only going to get > > 2HP from the shaft. But for a one-off where you find the motor > > and/or VFD cheap on eBay or a scrap-heap, it can work very well. > > I am sure you are right, but that wasn't my point. 240V single-phase > VFDs largely top-out at 3HP.
Doesn't need to be single phase input. A single-phase input VFD has modestly up-rated diodes and caps to handle the higher peak currents and ripple current that comes with a single phase operation. A larger three-phase input drive running at half or less of its rating doesn't need any up-rating, the parts are already large because the drive is large. You don't want a drive that will refuse to run on single phase. But I haven't encountered any such things until you get to 50-100HP or more. Smaller ones just have ordinary dumb diode bridges and no clue whether the input is missing a phase. If there is any form phase loss protection, it is likely based on looking at the cap bank ripple voltage because that doesn't require any extra sensors. Again, the derate helps. Running a 10HP drive at 10HP on single phase will cause a lot of cap ripple voltage, and the drive might well detect that and trip to save the caps. Running that same drive at 2HP on single phase is likely to have less ripple than running at 10HP on three phase. The detection algorithm won't have a clue. > > https://www.inverterdrive.com/group/AC-Inverter-Drives-230V/?filter=Input%7c230Vac+1ph > Does actually list some, I admit. But I am fairly sure that there > weren't any over 2.2kW last time I looked a couple of years ago. > > -- > atp > If you can't fix it, you don't own it. > http://www.ifixit.com/Manifesto > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- John Kasunich jmkasun...@fastmail.fm ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
