3 phase converter

Mar 18, 1999
I just acquired a Solberga Mekaniska drill press (model SEnr7). It of course if 3 phase and I need to get a converter. Any suggestions?

Surplus Center? Better source you may have?


What I did was build my own rotary converter, and if I can do it anybody can. Just do a little research online and perhaps visit your local library. Then go to the local scrap yard and get a 3 phase that is the same size or larger than the one you want to run. Scrap yards near industrial centers often have piles of motors that run fine that they sell by the pound at scrap prices. I picked up my 7.5 horse, which still had the factory tags on the leads (yes-it had never been used) for $22 :D

Two of the three windings in such a motor can run (unloaded) off 220 single phase, it just needs help getting started. On a converter unit this is accomplished with a start capacitor that is disengaged as soon as the motor comes up to speed. Now you will have two windings running the motor and the third will be picking up energy from the rotor and generating an out of phase leg. Tap into this and run it to the motors you want to run.

My rotary phase converter is one of the coolest things that I have built for my shop; this is because I know nothing about electricity, so I am in awe of it. I routinely run a 3 horse motor and a five horse motor off it while simultaneously running various fractional single phase motors and an arc welder -all on a 50 amp circuit! So the thing has to be pretty efficient as well.

There is one catch however; I cannot remember which is which, so perhaps somebody here can help out. There are two types of windings; there are delta type motors and "Y" type. One can be used for a converter and the other cannot. I think the "Y" type is what you want, but I cannot remember :confused: Either way it will have a symbol on the plate that tells you this. It will be a triangle for delta and "Y" with little circles on the ends of the arms for the other.
Yep you want a "Y" connected motor most American motors are "Y" connected. I think that most European motors are delta. but I believe that you can run a delta motor off of a rotary converter but not a static converter. A static converter is used to simply start a 3-phase motor and reduces the H.P. by around 35%. a Rotary actually supplies the third phase so no loss in H.P. it is not exact, but close. Best bet would be to buy a V.F.C controlfor motors up to 3 hp. (no welders allowed) All of the advantages of a phase converter with variable speed to boot.

I have some plans that i bought a while back. Email me and I will send them to you. It is pretty darn simple.