Phase converter question.

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Thann37

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Location
North America
Occupation
Electrician
My daughter bought a used embroidery machine without realizing it needs a 20 amp, 3 phase 240 V power source. The garage has a standard 120/240V 100 amp panel. Every phase converter I have found requires a 240V single wire supply, this cannot be done with a residential 120/240V system without a transformer.

Is there a simple and relatively inexpensive solution?
 
Can the motor or any components be changed to single phase? I guess you could use a VFD. But you can use a phase converter. You feed the phase converter with 240 single phase and get 3 phase out of it.

The 208 volt machine may or may not be compatible with 240 volt 3 phase. Depends what the machine has for loads.
 
You would be better off with a VFD for just one machine. They are readily available and less expensive than a RPC.

Welcome to the Forum!
 
A normal phase converter should work just fine with ordinary residential 120/240V.

Find an electrician who can figure out the machine internals and advise you on the best options for running on single phase
 
Thann37 said:
Every phase converter I have found requires a 240V single wire supply, this cannot be done with a residential 120/240V system without a transformer.
Click to expand...
Welcome to the forum.

There is no such thing as a single-wire supply. Phase converters accept two-wire single-phase supplies.

As with any line-to-line load that doesn't require the neutral, it's wired like a water heater or A/C unit.

A phase converter creates the third phase, fairly well resembling a real three-phase power source.

As the guys said above, a VFD is a better choice for a single, known, relatively-small load like yours.
 
ActionDave said:
While you can use a rotary phase converter or a VFD I would look into changing the motor. All you need to do is match the frame and horsepower. Oftentimes it's easier than the phase conversion options.
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if the machine uses a general purpose type motor it is easy to replace with a single phase motor. Some OEM motors are not so simple to do this with or may cost more to get an OEM motor to replace with than general purpose motor would cost.

This also sounds like a kind of machine that possibly could already have a vfd in it. I could see the need to change speed or even reverse it during operation on this kind of a machine. If so and they oversized the drive enough it may even be possible to direct feed it with just single phase supply.
 
Sewing machines for hand use generally have a wide range variable speed motor.
An embroidery machine with computer or mechanical control can usually run full speed all the time.
 
Eddie702 said:
Can the motor or any components be changed to single phase? I guess you could use a VFD. But you can use a phase converter. You feed the phase converter with 240 single phase and get 3 phase out of it.

The 208 volt machine may or may not be compatible with 240 volt 3 phase. Depends what the machine has for loads.
Click to expand...
So then a transformer to step up the 120V to 240V is needed? Every phase converter I have come across only has L1 and N connections.
 
LarryFine said:
Welcome to the forum.

There is no such thing as a single-wire supply. Phase converters accept two-wire single-phase supplies.

As with any line-to-line load that doesn't require the neutral, it's wired like a water heater or A/C unit.

A phase converter creates the third phase, fairly well resembling a real three-phase power source.

As the guys said above, a VFD is a better choice for a single, known, relatively-small load like yours.
Click to expand...
The machine has it's own speed control built in. Everything I have read states that a VFD might mess with the speed control.
Every phase converter I have come across only has L1 and N connections.
So then a transformer to step up the 120V to 240V is needed?
 
kwired said:
if the machine uses a general purpose type motor it is easy to replace with a single phase motor. Some OEM motors are not so simple to do this with or may cost more to get an OEM motor to replace with than general purpose motor would cost.

This also sounds like a kind of machine that possibly could already have a vfd in it. I could see the need to change speed or even reverse it during operation on this kind of a machine. If so and they oversized the drive enough it may even be possible to direct feed it with just single phase supply.
Click to expand...
The machine has it's own speed control built in.
 
Thann37 said:
The machine has it's own speed control built in.
Click to expand...
If the speed can be controlled over a wide range, chances are the motor is DC rather than AC or uses a commutator (universal) to make the speed independent of drive frequency with AC, and the speed control is just a resistor.
A series resistance with an AC-only (induction) motor simply cannot produce a 30:1 speed range.
And if the motor is DC or universal, the VFD has no control over the motor speed except by varying the voltage. It is not designed for that.

josepheoff.github.io

A sewing machine motor speed control - Musings on motor speed control for universal motors

Ideas for closed loop control of small universal motors.
josepheoff.github.io
 
Thann37 said:
Every phase converter I have come across only has L1 and N connections.
Click to expand...
You're looking in the wrong places then. Every RPC I have ever hooked up had L-L connections.
Try these folks: https://www.americanrotary.com/

They have a place to enter your required needs and you can select the RPC. Or, you can call them for help picking out what you need.
 
Last edited:
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USED Tajima TME-DC906

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Below are the two pictures I have right now. The first is the cord end that came with it. A phase converter was suppose to be part of the sales.
a20240314_110005.jpga20240314_112152.jpg
 
At this point, I think you need to contact the seller or the US distributor for support (it's a Japanese machine). That machine appears to be all electronic servo drives, so a VFD or static phase converter is certainly of of the question, and a rotary phase converter (RPC) may not help, either (depends on the rotary). My guess is that there are electronic power supplies connected between all three phase leads so running on single phase would required some internal reconfiguration.

A real motor-generator phase converter would work, but AFAIK many RPCs only derive the 3rd.

(I wasn't able to find much in the way of specs online, but did see some parts manuals and close-up photos.)
 
In the factory I worked in, we the electricians/technicians had to work on some of the equipment. We had those Tajima machines. I didn't know what kind of machine the OP had when I posted earlier, but I think an RPC would work. The motors are DC and are step motors. The machine is computer ran. You put a programmed disc in and set the parameters and it takes off. I never took the time to see what the 3ph was doing. My guess is just to divide/balance the load.
 
zbang said:
At this point, I think you need to contact the seller or the US distributor for support (it's a Japanese machine). That machine appears to be all electronic servo drives, so a VFD or static phase converter is certainly of of the question, and a rotary phase converter (RPC) may not help, either (depends on the rotary). My guess is that there are electronic power supplies connected between all three phase leads so running on single phase would required some internal reconfiguration.

A real motor-generator phase converter would work, but AFAIK many RPCs only derive the 3rd.

(I wasn't able to find much in the way of specs online, but did see some parts manuals and close-up photos.)
Click to expand...
I have a friend, with multiple machine tools, that has been using electronic Phase Perfect converters on his large table and rotary converters on his other machines.
 
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