On 5/25/2012 1:33 PM, Peter C. Wallace wrote: > On Fri, 25 May 2012, andy pugh wrote: > > >> Date: Fri, 25 May 2012 18:19:39 +0100 >> From: andy pugh<bodge...@gmail.com> >> Reply-To: "Enhanced Machine Controller (EMC)" >> <emc-users@lists.sourceforge.net> >> To: "Enhanced Machine Controller (EMC)"<emc-users@lists.sourceforge.net> >> Subject: Re: [Emc-users] Commutating Reactor >> >> On 25 May 2012 18:00, Dave<e...@dc9.tzo.com> wrote: >> >> >>> For only generating 1 phase (the missing leg) they are charging some >>> serious money for those inverters. >>> >> They are doing rather more than a typical inverter drive does. They >> create a smooth 3-phase waveform regardless of load. >> > > > I wonder if a VFD (with suitably tweaked parameters) and 3 inductors would > do. I suspect VFDs have fairly low switching frequencies (say 4-10 KHz) so > would need a fair amount of filtering > > Peter Wallace > Mesa Electronics > > >
Many 3 phase input VFDs will run if only two of the phases are connected - in other words they will run on single phase power. Usually the control voltage comes off of only two of the phases. I saw a web article a few months ago where a guy had connected a VFD to single phase and in order to fake out the VFD so it would function, he connected the third input leg to one of the other input legs via a power capacitor (metal can - continuous duty, etc) . I didn't save that link. If you put a filter choke (line reactor) after the VFD it would smooth the power output substantially. When I was with Siemens we had who did this and the standard recommendation was to oversize the VFD by 30-40%. But this was for smaller motor applications back then - 3-5 hp etc. This was before cheap single phase input VFDs were available for 5-7.5 hp motors. Automation Direct has a 20 hp 230 volt input VFD for about $1100. Add a line reactor for another $160 and give it a shot. They have a 30 day return policy. Plenty of time to figure out whether or not you can jury rig it into working. and a lot cheaper than a PhasePerfect. http://www.automationdirect.com/adc/Shopping/Catalog/Drives/DURApulse_-_GS3_%28230_-z-_460_VAC_Sensorless_Vector_Control%29/DURApulse_-_GS3_Drive_Units_%28230_-z-_460_VAC_SLV%29 We'd all cheer you on if you want to try this. :-) Dave ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
