Thread: 3 phase converter HELP !!!

Tweet

Anyone use a 3 phase converter, if so what type ? I got a 3 phase air compresser for a very good price but no 3 phase in the shop. I can replace the motor with a single phase.
Brad

How big a motor is it? you probably are better off/cheaper to change the motor out versus getting a phase converter. I have a friend that runs one because he has a machine shop but the units aren't cheap from what I remember him telling me.

Red

Phase converters are available in static and rotary style. Static converters are cheaper but also do not result in full motor power. Static converters only run wye motors, not delta motors as I remember. Depending upon your motor size, a rotary phase converter starts at somewhere in the $400 range for a 1 or 2 hp unit. The static converters are cheaper but much less efficient. Like Denny said, a motor change may be the easy way out. A 5 hp single phase motor draws 22.5 amps if my memory serves me....you would have to put it on a 30amp breaker with the correct size wiring. If the motor is bigger than a 5, the motor gets pricey.....this is why 3 phase stuff sells only to industrial power hookups.....

I ran two seperate Static converters to run my crank grinders for years. Not one problem ever. I would have preferred rotories but the statics were affordable and by rolling the dice, I got 17 yrs use out of them while grinding every day 12 hrs a day (still have the converters and they still work). It can be done watch your horsepower ratings and amp loads the thing is rated at. Good luck.

As all above have said you might want to check into just changing the motor.

Static converters have come a long ways in the last 20 years. The old ones were nothing more than a passive phase shift network to improve starting torque. Once rotating the motor was in a single phase mode for all intents.

Modern static converters are completely different animals, and are more properly termed VFD's (Variable Frequency Drives). They rectify (convert to DC) the incoming single or three phase voltage, then chop it back up to form the required AC supplied to the motor. They are/can be programmed for a soft start along with a speed that would limit the actual draw on your single phase power.

Not cheap, $250-500 (new from Graingers) for a 1-3hp single phase to three phase drive, but if the compressor you bought is of decent quality this may be the best approach.

Several are on ebay, just be careful in matching the horsepower and voltage requirements.

Cheers, Mark

I use this static converter to run a 3 hp spindle on the CNC 10-12 years old now. I had a rotary converter on the 3 phase South Bend lathe I had many years ago. I didn't have a bit of trouble with either.

Thanks guys, I think I will change out the motors, found a shop that will trade my 2 15hp 3 phase for 2 15hp single phase plus $500.
Brad