I have three rotary phase converters. The are all using a potential relay for the start caps and a relay that pulls in the mains. So I don't have to hold the push button and if the power drops out for a few seconds the phase converter does not try and restart without the start caps. I've not had the fun of blowing anything up when building them. They are all balanced phase to phase within a couple of volts. However phase to phase the run caps are very different in order to get the voltage phase to phase to balance. I can post some details if anyone is interested...
John Dave wrote: > Back when I put my 10 hp phase converter together, I found some charts > on the web someplace about suggested capacitor sizing. I found a cheap > supply of capacitors at Mendelson's in Dayton, Ohio > and bought a small box of them. I ended up using I believe, 4 - 330 uf > 330 volt units as starting caps and 4- 135 uf run caps. I use a push > button to start the motor and as long as I hold the button > down the starting caps are wired into the circuit. When the motor spins > up I release the button. I tried to use a voltage sensitive relay, > like the ones used on refrigeration systems and AC systems, but > it was not reliable probably due to the high current from the large > number of caps. There is also a motor contactor that seals itself in > via the button push. That way if the line power drops, the contactor > drops out and the converter idler motor and he > attached slave motors are powered down. > > The math relating to how this works gets even more complicated when you > consider the effects of hooking a 3 phase motor that you are going to > start (a slave motor) across the the idling phase converter motor. > For a brief period of time, the idler motor becomes a generator. The > rotor slows slightly and the energy in the rotor pumps power into the > three phases and spins up > the slaved motor. It works very well. > > During experimentation, it is very obvious when more starting capacitors > are required as the motor will simply not spin up. > Adding more run caps helps balance the phases but they never really > fully balance. > > Safety glasses are very good idea when experimenting. Starting caps > go off like firecrackers if you overstress them. They are only > designed to be switched in for a few seconds. > > A source of cheap starting caps is a really good idea if you want to do > some phase converter experimentation. I blew up several of them. > > Dave > > On 3/14/2011 9:01 PM, Jon Elson wrote: > >> >> >>> On 14 March 2011 10:50, John Thornton<[email protected]> wrote: >>> >>> >>> >>>> Is it not amazing that the hillbillies from backwoods Missouri with a >>>> 3rd grade education can make a rotary phase converter without all the >>>> math... >>>> >>>> >>>> >>> >>> >> Of course! The trick is the windings in the motor do all the math for >> you, all you need to do is hook up the wires. >> >> Jon >> >> ------------------------------------------------------------------------------ >> Colocation vs. Managed Hosting >> A question and answer guide to determining the best fit >> for your organization - today and in the future. >> http://p.sf.net/sfu/internap-sfd2d >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users >> >> >> > > ------------------------------------------------------------------------------ > Colocation vs. Managed Hosting > A question and answer guide to determining the best fit > for your organization - today and in the future. > http://p.sf.net/sfu/internap-sfd2d > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
