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Old 01-03-2011, 07:42 AM   #1
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Converting 3 phase equipment to single phase /VFD?


Hello,
I am new to this forum and want to learn something about converting three phase machines to single phase. Specifically, can you convert let's say a three phase drill press to single phase by changing the motor? Can you use a VFD, variable frequency device? My home is wired for single phase and I have mostly 110 outlets but some 220v outlets. I am interested in some woodworking equipment that is used, but has three phase motors. Your help is appreciated. Thanks.

jp

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Old 01-03-2011, 07:57 AM   #2
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Converting 3 phase equipment to single phase /VFD?


Yes you could convert to single phase by exchanging the motor.

A small number of motors can be reconfigured for single phase, usually with a substantial reduction in maximum power, by changing around the wires on the motor terminals.

There are also transformer containing modules that will create three phase current from a single phase source. You plug the module into a single phase receptacle and plug your tool or machine into the module.

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Old 01-03-2011, 10:53 AM   #3
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Converting 3 phase equipment to single phase /VFD?


VFD's/Inverters are by far the best option to derive three phase from a single phase supply. Its perfect for the tools you mention as they have one motor. If the equipment has more than one motor and an integrated control system, the VFD is not the best way to go.

Single phase motors cost more than three phase motors. This is what makes the VFD so popular in this type of application. Derating may apply. Usually motors under 5 hp require no derating as per most every inverter manufacturer.

VFD's are for motors and nothing more. VFd's are smart so can take the place of the existing control scheme also. Rotary phase converters while the most expensive route can supply 3 phase power for most anything, unlike VFD's. If you have one motor, the VFD is the best bet. The most economical too.
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Old 01-03-2011, 05:08 PM   #4
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Converting 3 phase equipment to single phase /VFD?


Go with the phase converter, I got an old milling machine from work they were gonna toss and a friend made me a phase converter out of an old 3 ph motor, just needed an outlet and a capacitor I believe.
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Old 01-03-2011, 05:11 PM   #5
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Converting 3 phase equipment to single phase /VFD?


IMO simply replacing the motor with a single-phase is by far the easiest and cheapest thing to do most times.
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Old 01-04-2011, 02:22 AM   #6
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Converting 3 phase equipment to single phase /VFD?


Quote:
Originally Posted by Speedy Petey View Post
IMO simply replacing the motor with a single-phase is by far the easiest and cheapest thing to do most times.
As long it is a common motour frame size it is not a issue.

The only time you will run into if you have really oddball motour frame or design then it may justify to get the VSD in there { yeah they have single phase input and three phase output }

To OP what type of motour itself you will have to find the nameplate for frame size , HP rating , RPM , voltage.

That is the basic items we will able look it up and see what simauir size to single phase motor and normally if you have alot of room and adjustment area then single phase motour will work fine due the single phase motor useally slightly larger than triphase motour is.

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Old 01-04-2011, 10:49 AM   #7
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Converting 3 phase equipment to single phase /VFD?


Quote:
Originally Posted by SubSailor View Post
Go with the phase converter, I got an old milling machine from work they were gonna toss and a friend made me a phase converter out of an old 3 ph motor, just needed an outlet and a capacitor I believe.
Those home made converters, motor and capacitor will work but will not produce the torque required to operate the motor at full load. Its not a true 3 phase sign wave. Its manufactured from one leg to make two. This is old school and we can do much better today. I have see this done and did it myself until I found out I could get a cheap VFD that works much better for very little money.

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IMO simply replacing the motor with a single-phase is by far the easiest and cheapest thing to do most times.
Its not that easy. Just like Marc said. The new single phase motor may not be on the same frame. Single phase motors are expensive with several parts that can fail. The small VFD also allows the operator to use either 3 phase or single phase.
IMO the VFD would be the most economical in the long run if not up front.
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Old 01-04-2011, 03:14 PM   #8
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Converting 3 phase equipment to single phase /VFD?


One comment-

Using one machine at a time, you could wire the VFD to run all the machines. I doubt you'll use all the machines at once anyhow.

As for transformers, capacitors, and such, it's cheaper to buy a new motor- although you can wire the phase converter to run one at a time, as well.

Don't forget any motors you pull out are usable salvage, and worth more money than scrap. Those 3 phase motors almost never wear out, especially if they've been greased at the bearings (the only moving part, pretty much).

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