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Forum topic by 6288 posted 07-05-2009 06:33 AM 922 views 0 times favorited 6 replies Add to Favorites Watch
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6288

4 posts in 2712 days


07-05-2009 06:33 AM

i just inherited an older table saw. Motor is missing plate. How do I tell if it is a single or 3 phase motor? Plug is three pronged 250/125. Thanks for any help you can offer.


6 replies so far

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TopamaxSurvivor

17671 posts in 3140 days


#1 posted 07-05-2009 09:58 AM

One of the prongs on the plug should be a ground. probably single phase. A 3 pahse motor will have a connection box on the side that will usually have 9 wires in it. could be only 3 or as many as 12, but usually 9. They will be connected together to 3 leads coming out. If its single phase the cord will usually go to a small connectioin box that is flush on the end of the motor.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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6288

4 posts in 2712 days


#2 posted 07-05-2009 08:34 PM

thanks. the motor has 6 wired coming out if it. it is wired to a three wired (B,W, G) 250 plug. The wired coming in is grounded green to the motor. the on off switch has three termanils and says on the side

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TopamaxSurvivor

17671 posts in 3140 days


#3 posted 07-05-2009 10:57 PM

It should be a single phase motor. The green should be the ground. I can’t of a reason for a 3 phase motor to bring out 6, you couldn’t change the voltage for the motor.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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TopamaxSurvivor

17671 posts in 3140 days


#4 posted 07-05-2009 11:33 PM

Suppose I’d better correct that statement ;-)) The new drive rated motors do bring out 6 wires on 3 phase motors, but the old ones don’t.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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6288

4 posts in 2712 days


#5 posted 07-06-2009 02:00 AM

so a single phase you can change voltage, 3 phase you can’t?

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TopamaxSurvivor

17671 posts in 3140 days


#6 posted 07-06-2009 02:23 AM

You need 9 wires to change a 3 phase from high to low or vice versa. I don’t remember exactly what the connections are for single phase. Never did enough of them. Some are dual voltage and some are reversible when the proper wires are brought out to the connection box.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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