Phase converter

Farmer Phil said:
Hi friends,

Although I don't need this at the moment, http://honolulu.craigslist.org/oah/tls/1057416140.html, it looks like it would be good for me to pick this up if I can. Any thoughts???

Thanks, Phil
Click to expand...

Phil,

My understanding (self taught, not job related) is you would lose 1/3 of the hp/torque using a phase convertor. A phase convertor will start a 3-ph. motor (3 power legs) on two legs but can only run it on two legs.

I've a good friend who runs his home-shop, a 9" Clausing, #1 Bridgeport, Hardinge Precision Lathe, and a small surface grinder on phase convertors. The surface grinder motor over heats but not seriously, the Hardinge (2spd. gear box and infinite variable speed) bogs at the lower end of the lower gear (not the end of the world) and the Bridgeport mill & Clausing late run fine.

I think, if you can slightly over-motor for your use, a phase convertor will work OK. A VFD is the elegant solution... full power and variable speed. A rotary phase converter would get full power. VFD's are cheaper and cheaper. Might be a bad economy would get a person a VFD deal-of-a-life-time.

Mike
 
Hi Phil,
I acquired a Bridgeport with a 5 hp 3 phase on it several years ago and decided to build my own static phase converter....after much study and some educated guessing I was successful in building it! The thing I descovered was that the capacitors used have to be the right amount of mfd's to balance the three phases...the third leg of the three phase is produced by the capacitors so different size motors require different combinations to balance all three legs of the motor circuits for optimum performance....not hard but does require some tweekin! The ready made ones work with in certain motor sizes and yes ya only get about 5/8's the rated power output of the given motor....hope that helps!
 
Thanks Guys,

I thought this is a rotary phase converter. No? And that would mean "full power." In other words, it would power a motor up to 3 HP (in this case) and get 3 HP. No?

Thanks, Phil
 
Farmer Phil said:
Thanks Guys,

I thought this is a rotary phase converter. No? And that would mean "full power." In other words, it would power a motor up to 3 HP (in this case) and get 3 HP. No?

Thanks, Phil
Click to expand...

Phil, I'm a dumbass... I only looked at the second picture, saw "Phase-a-Matic" and assumed it was a static phase converter... the ones that lose hp rating because they don't truely run three equal legs... because that company has made billions of them.

In the realm of rotary phase converters, I think I've read there are variations (better and less better) in design. I don't know anything useful about them beyond that. There are some electric motor forums as helpful as this one but I don't have links to give you.

Mike
 
Farmer Phil said:
Thanks Guys,

I thought this is a rotary phase converter. No? And that would mean "full power." In other words, it would power a motor up to 3 HP (in this case) and get 3 HP. No?

Thanks, Phil
Click to expand...

Hello Phil,

Yes, a rotary phase converter will allow you to run full rated HP power. I have a 7.5HP rotary phase converter to run a 7.5HP 3 phase motor at full power. Static phase converters run about 2/3 the rated power. Here is a cool link if you want to make a rotary phase converter out of an old 3 phase motor --> http://www.metalwebnews.com/howto/phase-converter/3-phase.pdf

Eric
 
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