John, I would like to know more about the way you have engineered your phase converters. I am in the process of adding this capability in my shop.
Thanks, John R. Crane On Thu, Mar 17, 2011 at 5:53 AM, John Thornton <[email protected]> wrote: > 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 > ------------------------------------------------------------------------------ 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
