I have acquired certain pieces of equipment that had come out of a factory or school enviroment. Note:I will be adding pictures of them to web site at a future date. They had been running on 3-Phase power 220 volts AC. So out of necessity I needed to build a couple of 3-phase converts. In a single family house all we have coming into the home is 220 volts single phase AC. Years ago I had traded a old machinist friend of mine out of a old South Bend Lathe. It was pretty much in shambles. I cleaned it up and painted it. The machine turned out pretty good. I then needed to get it running so my machinist friend said that I could put a starting capacitor with a running capacitor across the third wire and that would run the motor. So I made a box and put a monetary push switch to switch the starting capacitor in the circuit. It worked and I used the lathe in that configuration for a long time. When I took the family to New York I had not used it in along time. Mostly because of my career and my family was pretty young. I decided that we could use money so I sold that old lathe.
Well I recently got interested in doing machine work again and had a chance to buy a Chinese lathe. I need to make some collets for a weather station that I was building. You just can not find those types of parts in a store or catalog. That is what I told my wife anyway. That was the justification for the new machine. So that is how I got started in buying all of this used equipment and the requirements for the phase converters.
I had attended a auction and they had two 9" South Bend Lathes that had come out of a school. So I started biding on one and got it. I knew that it had a 3-phase motor but I thought worst case I would buy a new motor for it. I started looking on the internet and I found some good information on building a converter. I had a friend of mine that has a brother in-law working for a heating and air-conditioning business. He got me some use capacitors and a potential relay. The capacitors that I tried to find were close to 70 MF. The general rule is 70 MF to 1 HP. The Potential relays are normally used in air-conditioners. The contact is normally closed. If you have any old air-conditioners do not throw them away until you stripped out the parts. I then got my first 3-phase converter to work. The following is a picture of the circuit: Note: I used the top circuit.
If you look at the schematic you will notice that the neutral is hook to the relay. The relay is normally closed. This connects the starting capacitor to the 3rd phase. As the motor comes up to speed there is a potential or voltage on the 3rd phase and that entergizes the relay and removes the capacitor from the circuit. I built two of this type and went a little further with the project. I had a friend of mine that was running in to the same problem that I had, getting equipment with 3-phase motors and he bought a commercial unit. Not to be out done. I build an automated one, but I can not give out the design because it was not mine orginally. Here is a picture of it being assembled:
This is a home made box. I will talk about making boxes in one of the other sections on machines. I get the metal free from my friends brother in-law that works at the heating and air-conditioning business. I used mostly used components, built the box and etch my own circuit board to build these units. This project really turned out well.
I have one lathe, milling machine and a surface grinder running with these converters. I have also made a couple of extra ones for any new machines that I acquire.
Hope you enjoyed the projects.