Author Topic: Single to 3 phase converter  (Read 6388 times)

mike90045

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Single to 3 phase converter
« on: October 27, 2009, 11:23:52 PM »
I hope this is useful to someone.  Mike


http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
archive:
http://web.archive.org/web/20080705071429/http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

BUILDING A PHASE CONVERTER
Includes Self Starting
By Jim Hanrahan
  Excerpt:
Many quality used industrial machines are available at attractive prices that have 3 phase electric motors. Most residential homes do not have access to 3 phase electric power at a reasonable price. If the home shop builder decides to use these machines they must either replace the 3 phase motors with single phase motors or find a way to use the single phase power at their house to run them. This article explains how to build a rotary phase converter that will convert your single phase 220 VAC electric power to 3 phase 220 VAC to power your industrial machines.

Safety should be your first concern and any electrical wiring should follow your local electrical code. That being said, some typical wire sizes, overload, and short circuit protection methods will be described to get you started. Also, the metal frame of the motors and your machines should be grounded. This safety ground normally does not conduct any electricity. It is present in case a current carrying conductor accidentally touches the metal frame. This provides a low resistance path for the electricity to flow instead of going through your body to earth ground.

There are two basic types of phase converters on the market which will allow 3 phase motors to run using single phase input to the converter. These types are referred to as static and rotary. The static converter is basically only a start circuit that once the motor starts, disengages and lets the motor run on single phase power. The disadvantage of this method is that the motor winding currents will be very unbalanced and the motor will not be able to run above about two-thirds its rated horsepower. The rotary converter provides current in all 3 phases and although not perfect, will allow a motor to provide all or nearly all its rated horsepower. If the motor has a service factor of 1.15 to 1.25 then you should be able to use full rated horsepower. The service factor can be found on the motor nameplate and is usually abbreviated S.F. The reasons that the electric power is not perfect are very technical and can include small amounts of voltage and current imbalance as well as the phase angles between phases not being perfect. The voltage and current balancing is straight forward if you have access to a voltmeter or preferably a clamp-on type ammeter. But even if you don't have these meters, using the approximate values of run capacitors specified in this article the currents should be close and you will be able to get nearly full horsepower from your 3 phase motors.

Doug

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Re: Single to 3 phase converter
« Reply #1 on: October 27, 2009, 11:38:20 PM »
Just a brief scan of the document but ity looks like this author read a book by Dave Jackson called Rotating Machines Drives and Power Systems.
Infact I think much of this document was lifted from Mr. Jackson early 1970s text book
It's a Good Life, If You Don't Weaken

gpkull

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Re: Single to 3 phase converter
« Reply #2 on: October 30, 2009, 11:25:32 PM »
vfd with single in 3 phase out is another option. vfd = variable freq. drive. practical machinist.com has a section devoted to making 3 phase from single and all different ways to do it. rpc is easy and cheap, there is a way iwth transformers, phase perfect (pricey i hear), i would stay away from static once the smoke comes out it wont go back in

jzeeff

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Re: Single to 3 phase converter
« Reply #3 on: January 15, 2010, 02:48:36 AM »
I second that - just buy a VFD and pick up variable speed too.