Sorry to ask a really dumb question, but 3 phase 60 Hz AC synchronous motors seem to start and run just fine on fixd 60 Hz frequency, why does one need to ramp up and have precise feeback of rotator postion therefore frequency and phase to make a D C controller? Of course, the anwer is efficiency, precise engine control and so forth, plus to preserve starting torque Which is of course HUGE in an AC compressor motor.
But ignoring all these must haves,... if one just hit an unloaded 3 phase motor with DC derived 3 phase sinusoids, would it not just run? So is it just the need for starting torque that is the big reason why one needs the complexity of rotoro feedback? No, challenging anything, just looking for a simply layman's overview of the need. Thanks Bob -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of Bill Dube via EV Sent: Thursday, June 11, 2015 5:08 PM To: Joe; Electric Vehicle Discussion List Subject: Re: [EVDL] DIY EV air conditioning? Did realize the Prius was permanent magnet. The TECO VFD might not work at all driving a PM. :-( Other OEM EV compressors might not be PM. Residential HVAC compressors are definitely not PM, but they tend to be rather bulky. Bill D. On 6/11/2015 11:54 AM, Joe via EV wrote: > Regarding an off-the-shelf VFD for a prius compressor, it would have > to be one that can control permanent magnet synchronous motors with > interior magnets. The TECO drive linked appears to only work in > sensorless mode for induction motors. Open loop V/f would probably > make a prius compressor spin, but probably not very efficiently or effectively at high power. > > Also, I've measured up to 1500W (2 HP) drawn by the prius compressor > on a 100F day with the fan on high, so the drive would have to be > sized accordingly. Looks like the 2 and 3 HP versions of the TECO > drive aren't much more expensive, though. One of those drives might > work with a residential hvac compressor. > > Also, I forgot about masterflux drives and compressors. They're > expensive, but I think they work well based on some posts on diyelectriccar. > > On Thu, Jun 11, 2015 at 7:03 AM, Bill Dube via EV <[email protected]> wrote: > >> "Hacking" some OEM EV air conditionaing, like from a Prius, is likely >> the best option. There are also inverter driven (VFD) home >> compressors that would likely work as well, but aren't as rugged as >> the OEM EV air conditioning compressors. >> >> I would investigate small, single phase input, three phase output, >> variable frequency drives (VFD) instead of building my own inverter >> from scratch. Like a TECO: >> >> http://www.surpluscenter.com/Electric-Motors/3-Phase-Motors/Variable- >> Frequency-Drives/1-HP-TECO-VFD-115-VAC-1PH-INPUT-3PH-OUTPUT-11-3424.a >> xd Likely will run nicely from DC. Certainly cheap to try. >> > -------------- next part -------------- An HTML attachment was > scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150611/fa > cd19a7/attachment.htm> _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA > (http://groups.yahoo.com/group/NEDRA) > > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
