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How do you convert or rewire a 5hp 3 phase motor to a single phase motor?

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2010-08-22 10:19:23
2010-08-22 10:19:23

Three-phase motors will run on single-phase power. What they WON'T do is start. There is no easy way to re-wire such a large motor to run on a single phase.

Properly sized capacitors and a special relay is sometimes used on sewage lift stations (poopie stations is what we call them) to run the 3-phase pumps on single phase.

I've seen 10 hp motors used. Sometimes a lift station is needed where 3-phase power is not available The motor will not develop it's full horsepower, only about 2 thirds. A push-button can be used in place of the relay, but you will have to push the button until the motor starts then let go. If the motor stops you will need to push the button again. Usually expect several hundred micro-farads to be needed.

I have used old A/C motor-run capacitors in parallel to experimentally determine the actual size (capacitance) needed. Be sure to use correct working voltage capacitors. DANGER!!! Electricity can EASILY kill you and capacitors can blow up in your face!!!

I've seen crazy people attempt to rope-start three-phase motors (it works), connect phase converters, all sorts of weird stuff. In reality, single-phase 5hp motors are available, so the a good recommendation is to trade-in the 3-phase motor for a 1-phase motor of the size you need.

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To run a three phase equipment from a single phase source, you will need something called a "phase converter".

Before you go out and buy one, find out if a single phase motor is available to match your requirements. It will probably be an easier solution for you if you can do that.

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Depending on your application, another option with such a large motor is to get a "Variable Frequency Drive". These are somewhat expensive but will take in a single-phase input and output 3-phase.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

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The winding design of the motor will not economically allow this to work. You would have to drive a 3 phase generator to supply it.

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Many electric motors have a single phase connection available. If not, there are a few choices but I would suggest hiring an electrician to do the work.

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I assume that by two-phase, you really are talking about a supply with two hot wires and a neutral, such as 120/240 volt. This is single phase power, it just has power taps on both ends of the transformer winding, the neutral is the center tap. I don't think it is possible to convert or rewire your motor. A large 3 phase motor must be run on a 3 phase electrical supply. It will not run and will overheat if you try to connect it to a single phase supply. The only way to make a 3 phase supply from a single phase supply is to use a converter like a motor-generator set. That would be way more expensive than getting a new motor.

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As far as I know you cannot . You can however get a phase converter which takes 220 volt single phase input and converts it to 3 phase output.

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you dont you have to buy a step down transformer or a new motor


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