My simple phase converter

[twowheelinjim]

Here's a picture of my electrical fire hazard waiting to happen...
It's a simple 5 HP 3 PH motor that is started by a 220 single phase motor via a lawn mower belt. It cost abot $300 in parts and has been in use for over one year.

 

[Rbeckett]

Two Wheelin,
do you have a diagram of that? Also the top motor is driving the bottom motor, right? I'm still learning phase conversion, so I am an idiot with the questions.
Bob

 

[twowheelinjim]

I'm probably the least capable person to expain this converter. 220 power is fed into the square D junctiuon box where it powers the 220 single phase motor. the switch in the middle turns on the single phase motor and it starts to spin the three phase motor. Once the three phase motor is running the switch is turned off thereby shutting the power to the 220 single phase motor. I had read about these contraptions on the internet so I started collecting the necessary parts with hopes of building one. As I got to collecting, I found an ad on CL for a phase converter. The man came over and installed what you see in the picture and took what parts I had since I probably didn't need them. All in all, I have my machines running, I didn't get electrocuted, and 75 year old man got the satisfaction of making me feel like a jackass for not figuring this thing out myself. Then he tried to take my old Harley since he figured I don't ever ride it.

 

[7HC]

220 power is fed into the square D junctiuon box where it powers the 220 single phase motor. the switch in the middle turns on the single phase motor and it starts to spin the three phase motor. Once the three phase motor is running the switch is turned off thereby shutting the power to the 220 single phase motor.

So what keeps the three phase motor running once the single phase motor is no longer turning it?
I'm probably at the same level as Bob.

M

 

[burnrider]

No, you two are doing all the work for the rest of us.
I don't understand shutting down the single phase slave motor while still getting continuous 3 phase machinery power.

 

[ScrapMetal]

As I understand this kind of setup (going out on a limb here ) you appy single phase power to both of the motors. You apply it first to the "starter" motor to get the 3-phase motor up to speed. Once the 3-phase motor is up to speed you can apply the single phase power to it and it will run on the single phase but also out put 3-phase power. Once the "big" motor is running on its own you power off the starter motor and ideally disconnect it/loosen the belt so that it is no longer turning.

Then he tried to take my old Harley since he figured I don't ever ride it.

I hope you ran him off waving a jiffy stand towards his head! :thumbzup:



-Ron

 

[twowheelinjim]

Sorry, I forgot to mention the sequence of events to start the power. First I flip on the toggle switch to get the smaller motor going (220 volt, single phase). Once it has achieved full RPM, I throw the switch lever on the Square D box. This sends power to the 5 Hp 3 phase motor, getting it spinning. Once the three phase motor is is running at full RPM, I switch off the smaller motor via the toggle switch. In the past I have accidentally switched on the three phase motor without first getting it spinning and it makes an awful sound like a whale farting or something. It can't be good for the motor, nothing that makes that sound usually is....:nono:

The guy who put the converter together makes them as a way to keep busy while retired. I didn't know there was such a need for these things in woodworking...My next big project is to rewire my entire shop utilizing conduit and adding airlines. Last year I hauled off 8 or 9 hundred pounds of scrap conduit that I could of used but I was not thinking ahead-now I'll have to pay for the stuff.:angry:

 

[twowheelinjim]

I forgot to mention he's still after my bike. He offered me a plunge EDM machine with all the bells and whistles including a planetary head for burning in threads in hard material. I just can't think how often I would need an EDM. I did mention to him that I wouldn't mind trading for a CNC mill...

I just remembered, I think 220 single phase is wired into two of the three legs on the 3 PH motor and when the motor starts to spin, it creates the third leg. I could be wrong though..

 

[8ntsane]

If your interested there is a better way to start your single phase motor with one switch. Also you can get a one way bearing the will spin in one direction. If you shut down the start motor the pulley will continue to spin and not the motor. BTW your start motor is probably generating power. I built one with the one way bearing and adjusted pulley size to just below the RPM of the pony motor so that when a load was put on the RPC motor the pony maintained speed and kept the output constant.

Frank

Frank

The bearing you are speaking of, is that what is referred to as a sprag?

 

[Philco]

At one point I was Like many of you that don't understand a rotary phase converter & how to start it. My fear of the unkown kept me using a static phase converter to power my milling machine for several years. When I bought my lathe,I decided that I needed to learn how to make a RFC so that I could power the mill, the lathe,& a Baldor tool bit grinder that I had purchased. I searched the net & found several wiring diagrams. After taking the wiring diagrams & breaking them down into smaller sections & studying them I realized how simple it really is. My advice to anyone that wants to build a RFC is to start with finding a3phase motor first. This will probably be your most expensive item. Forget about all of the details that you don't understand right now because what you don't understand will be the very thing that keeps you from ever getting started. Once you find a 3 phase motor let us know & we will help you make the next step. Froneck & others seemed to have quite a bit of knowledge about RFC & I'm sure they would be glad to share their knowledge with any one that's trying to build one. Your first step is to find a 3phase motor that's at least 1.5 times larger than the largest motor on the machine your trying to run. Example= lathe motor is 5 HP.
5 HP lathe motor multiplied by1.5= 7.5 HP phase converter motor or larger. Also make sure the motor can be wired for high or low voltage. Some 3phase motors are wired for 440 volts only. I had a friend that had a10 HP motor that I got for free & the rest of the stuff came from the scrap yard. I have it mounted next to the lathe. I walk up to it, turn on one switch, press the start button & within 2 seconds I'm on 3phase. I hope this gives others Some encouragement to build a rotary phase converter.
Phil.