Four wire motor To phase or three???

Thread Starter

Acmechanic9

Joined Jun 24, 2020
6
I have recently bought some older equipment and Motors Say three phase but there are four wires coming out of them. The first I need it running immediately so I took the motor in to A Motor specialist Because I was unable to find any information on how to wire it. The nameplate wiring schematic showed six tabs yet there were only four wires. The guy in the shop rewire the motor for three phase and said that it was a single phase motor conversion back sometime ago. I had never heard of two phase before looking in the control box of one of these machines And they mentioned two phase wiring. I don’t believe Motor I took in was single phase I believe it was two phase. Are these motors wired hot1, neutral2, hot3, neutral4??? Or do you believe they are three phase that requires a neutral ? Sorry if it seems like a stupid question but All four pieces of equipment have motors with four taps coming out I really don’t wanna spend $1000 a piece to have them all rewound can someone help me???
Thank you
 

Thread Starter

Acmechanic9

Joined Jun 24, 2020
6
This particular item is hey Shear there were several items similar Motors With four wires All metal working equipment. The plate shows nine wires on each motor again there are only four. Here’s a couple photos I opened up the mag starter just to follow back the wires maybe you can help me out. The guy at the place I have to repair motors said they had been rewired for single phase which is fine because I have a rotary converter feeding all my three-phase machines much easier for me if it was single phase. I thank you for Any suggestions.
 

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Thread Starter

Acmechanic9

Joined Jun 24, 2020
6
Thank you for the literature, I read page 20 not seeing any info on wiring a motor with 4 leads, and shouldn't this motor have nine coming out or at least a place to tie lugs together for high and low voltage? Not following
 

GetDeviceInfo

Joined Jun 7, 2009
1,732
The best clue would be how it was wired through the starter. Ohm your leads, looking for two windings, indicating a split phase rewind. Does it just use a single contactor? Two contactors may indicate soft start.
 
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nsaspook

Joined Aug 27, 2009
7,482
Thank you for the literature, I read page 20 not seeing any info on wiring a motor with 4 leads, and shouldn't this motor have nine coming out or at least a place to tie lugs together for high and low voltage? Not following
We can only use the plate for what was originally the motor configuration. With a motor internal rewire those 4 wires could be 3-phase with neutral or a single-phase hack.
http://www.gohz.com/3-phase-motor-running-on-single-phase-power-supply
 

Thread Starter

Acmechanic9

Joined Jun 24, 2020
6
The best clue would be how it was wired through the starter. Ohm your leads, looking for two windings, indicating a split phase rewind. Does it just use a single contactor? Two contactors may indicate soft start.

Was controlled with a mag starter, There is continuity between wires 1 and 3 also between 2 and 4. My ohm meter was damaged going to go replace it in about an hour.
 

GetDeviceInfo

Joined Jun 7, 2009
1,732
Was controlled with a mag starter, There is continuity between wires 1 and 3 also between 2 and 4. My ohm meter was damaged going to go replace it in about an hour.
Are the two winding then connected in parallel on the contactor? If so, then likely a split phase winding. I’ve seen this come about on rewinds when the wire to wire voltage can’t be maintained as in the original winding, or if a soft start option is utilized in a two step, no load start.
 
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Thread Starter

Acmechanic9

Joined Jun 24, 2020
6
Are the two winding then connected in parallel on the contactor? If so, then likely a split phase winding. I’ve seen this come about on rewinds when the wire to wire voltage can’t be maintained as in the original winding, or if a soft start option is utilized in a two step, no load start.
Here is how the mag starter is wired
 

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Reloadron

Joined Jan 15, 2015
5,612
Based on your images you have a 3 phase motor. The 4th lead is ground and the six terminals are for configuring the motor for 220 or 440 volt operation. You can tell it's an older motor as most industrial 3 phase today is 480 which your motor will run fine on or 220 will also do fine. I assume you have 3 phase 220 or 480 volts available and if so is your power a WYE or Delta configuration? You also posted a picture of a Square D motor starter/contactor. I have no idea who your motor specialist is but I suggest you find a new one. Finally if you wire and power the motor and it turns the wrong direction for your needs just reverse the wiring of any two phases.

Ron
 
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