Old motor - single or three phase?

Thread Starter

ryanjg117

Joined Nov 3, 2017
35
Bought an old Powermatic sander from auction today and sadly noticed it was three-phase after the fact. (My shop only has single phase.) The connector is certainly three phase (twist lock with four prongs) but upon looking at the old motor label, I'm wondering if it could be rewired for single phase? The label reads "1" for "PH." I've tried to decode the model from Marathon's website, but it's a bit confusing. I'm not very knowledgeable about motors, but noticed there were a couple different wiring diagrams on the label. Any ideas if this can be wired for single phase? Pics attached.
 

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Thread Starter

ryanjg117

Joined Nov 3, 2017
35
Does this mean it can be wired for 220v single phase in addition to three phase?

Suprised to see the date code apparently denotes the motor made in October of last year as well.
 

nsaspook

Joined Aug 27, 2009
9,459
Does this mean it can be wired for 220v single phase in addition to three phase?

Suprised to see the date code apparently denotes the motor made in October of last year as well.
It's a single phase motor per the plate. You can tie the winding in the parallel configuration for 110vac single phase or in a series configuration for 220vac single phase.

 

Thread Starter

ryanjg117

Joined Nov 3, 2017
35
Odd, so maybe they just put the wrong plug on it. I'll check the conductor but another giveaway would be only three wires (rather than four). Correct?
 

MaxHeadRoom

Joined Jul 18, 2013
24,993
I think the thing that is confusing you is the connections where no power is applied, it plainly shows 110v/220 single phase as previous post show.
NOT 3phase!
There would normally be a capacitor mounted to the frame.
Max.
 

Tonyr1084

Joined Sep 24, 2015
6,866
Just looking at the wiring diagram, it clearly shows L1 & L2. Likely the reason for the four pin plug is for L1, L2, N (neutral) and G (ground). At least that's how I would take it. I'm not the expert on this so don't take what I say to the bank, but the mere fact that the diagram shows L1 & L2 suggests to me that this is how you would wire it for 220 VAC. Again, I'm not the expert here.
 

nsaspook

Joined Aug 27, 2009
9,459
Just looking at the wiring diagram, it clearly shows L1 & L2. Likely the reason for the four pin plug is for L1, L2, N (neutral) and G (ground). At least that's how I would take it. I'm not the expert on this so don't take what I say to the bank, but the mere fact that the diagram shows L1 & L2 suggests to me that this is how you would wire it for 220 VAC. Again, I'm not the expert here.
Correct, the no L3 is a big clue on the above motor. :D

This is a typical three-phase plate for dual voltage.
 

shortbus

Joined Sep 30, 2009
9,324
The connector is certainly three phase (twist lock with four prongs)
Just having a twistlock plug doesn't automatically make it 3PH. If this came from a private party he may have not wanted the expense of putting a new cord and plug on it when changing the motor. And since his shop only had 1PH he knew it would only ever be connected to his outlet.

Twistlock plugs are available for many different voltages, amperage's and types of power, some are even used on DC..
 

nsaspook

Joined Aug 27, 2009
9,459
Just having a twistlock plug doesn't automatically make it 3PH. If this came from a private party he may have not wanted the expense of putting a new cord and plug on it when changing the motor. And since his shop only had 1PH he knew it would only ever be connected to his outlet.

Twistlock plugs are available for many different voltages, amperage's and types of power, some are even used on DC..
Exactly. You need to know the exact type. We have a whole shelf of X Blades—Turn-Lock—Grounded types just for single phase connections.
https://www.mcmaster.com/catalog/125/843
 

Tonyr1084

Joined Sep 24, 2015
6,866
He could also have had a 230v 3ph and GND outlet handy, and just use two phases for 1ph. motor.
Max.
How would you use two (of three) phases? From what I can envision, L1 & L2 (in my home) make 240 VAC but they are in phase. L1 to L2 would be a single phase 240 VAC whereas L1 & Neutral (center tap) gives you 120 VAC. (same with L2 & Neutral, it's just a center tapped transformer) Wouldn't 2/3 phase be 120˚ out of phase?
 

nsaspook

Joined Aug 27, 2009
9,459
How would you use two (of three) phases? From what I can envision, L1 & L2 (in my home) make 240 VAC but they are in phase. L1 to L2 would be a single phase 240 VAC whereas L1 & Neutral (center tap) gives you 120 VAC. (same with L2 & Neutral, it's just a center tapped transformer) Wouldn't 2/3 phase be 120˚ out of phase?
No.

 

MaxHeadRoom

Joined Jul 18, 2013
24,993
As per nsapook's DWG, across any two phases is single phase, IOW any two are 180° apart as there is no other reference, same as your L1-L2.
Max.
 

Thread Starter

ryanjg117

Joined Nov 3, 2017
35
Thanks all - I pulled the plug off last night and indeed it's just only three-conductors in the cable, even though they attached a NEMA L15-30P twist-lock plug for 3-phase machines. I'm guessing they got lazy and just slapped a random plug on it before sending it to auction. Good news for me, though. I just need to get a single phase twist lock plug on it and (hopefully) it will fire right up.

Also, the motor definitely has the capacitor mount as well.
 

MaxHeadRoom

Joined Jul 18, 2013
24,993
22amps on 110v and 11amps on 230, if running off of 230, you can get the 230v 1ph 15a socket, for 120v you may get away with a 20a socket as the 22amps is not continuous in typical use.
30a Breaker to suit.
Max.
 
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