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I just ran my Unisaw w/220v....motor was wired for 120!!! What now?!!!

5K views 17 replies 7 participants last post by  MrUnix 
#1 · (Edited by Moderator)
Well I said it all in the title. I am losing my mind. I rebuilt the motor, bearings, brushes, spring. Wired back up the way it was before, but with a new paddle style magnetic switch. (1956 Unisaw w/ bullet style motor, 3450 RPM repulsion induction) I ran it with the new switch for a few cuts. Then….nothing. Checked the power at plug, there is juice. Just stumbled across a wiring diagram on this forum for a saw of the same vintage as mine and….ug. I ran 220 through my motor while wired for low voltage. How do I check motor? Nothing is working.
 
#4 ·
Yeah, I am making this confusing.

Full story.
Saw worked great at last shop. Moved it. Plugged it in and ran great for 30 seconds. Blew a double 30amp breaker. Thought it was a motor draw at start up. Went to a double 50 amp. ( 10 guage wire). Saw ran great for 30 seconds then the contactor connections started smoking. OK. Rewired motor, switch and contactor. Ran for a minute, smoked.

Pulled motor and put in new brushes, spring, turned. Put motor back in, and now with a new simple paddle switch. Ran great, did around 6 decent 3/4 ply cuts…went for 1 more. Nothing.

Saw a pic of wiring at motor on this forum and, smacked hand against forehead. Doh!
Motor has no tag, I was told by Electrician at last shop it was 220 wired.

Figured I fryed the switch so put the original contactor on. Switched wire connections at motor for high voltage. Plugged into 220 outlet, hit "Start" button…..nothing.
 
#6 ·
Well, that doesn't help much :)

Verify you are getting voltage to the motor. If you are, then you probably toasted the windings. A dual voltage motor (120/240v) is designed to use 120v across the windings (even when wired for 240v operation), so pushing 240v through them isn't really a good thing. I don't think this will help, but here is a video of running a 120v motor on 240v - it didn't last too long:

Running a 120V motor on 240V

Cheers,
Brad
 
#7 ·
Years ago there was an infomercial for one of those hand-held cup blenders, the ones that kind of look like a milkshake mixer blade on the bottom, and have a rounded body that you hold in your hand. Hamilton Beach is big into them, I think. Very handy, portable, rinse the blend end off in the sink and you are done.

Well, this one off brand, they started getting returned a lot, and finally, one of the two people on the commercial, (the guy, I think), admitted that they were running the units on the set at 220VAC to get more punch out of them. They won't turn any faster since it is all 60HZ, but the torque is way up there and the motor overheats quickly. They would use it for maybe 20-25 seconds, finish the blend, and put that one below the counter. Unbeknownst to the audience, they would pull up a brand new one for the next mix, again hooked into 220VAC. He said they went through quite a few in one shoot.

My guess is you've toasted your windings. I rewound a lot of motors when on active duty in the US Navy, and saw my fair share of overvoltage motors where the windings shorted out and that was that…
 
#10 ·
OK, next question. I now have a 3phase bullet motor with 9 black leads. It is wired for 440 and I want it wired for 220. Any steps to follow before I start searching YouTube? I just checked owwm.org and can't find the info.
 
#13 · (Edited by Moderator)
Are any of the wires labeled and does the motor have the data plate with wiring diagram… pictures would help. If the wires are not labeled, then you could start by trying to figure out the winding pairs with a meter, which would give you a hint. You might also want to post this query (instead of just searching) over at OWWM as I'm sure there are a bunch of folks there with the same motor and might have faced the same problem. At any rate, here is something that may help a bit:



Cheers,
Brad
 
#15 ·
Brad you are the man. Your info has helped me with every post. I was having issues with creating an account on owwm. Got terribly annoyed with it. Would love to join in. Thanks again Brad. I have printed out the graphic you provided.
 
#16 · (Edited by Moderator)
No problem.. glad I could help. It may take a bit for them to approve you over at OWWM, but they are a wealth of info for old machinery and the Unisaw in particular. In addition to the old woodworking and old metalworking forums, there are several other forums that can only be accessed by members, such as the BYOD (bring out your dead, which is the buy/sell/trade/swap forum) and one specifically dealing with electrical issues on these old machines. Give 'em a bit of time and eventually you will get approved. Another good resource for old machines, if you haven't already discovered, is the VintageMachinery site, which is considered the 'mothership' for OWWM, and where you will find manual reprints and other documentation, a wiki knowledge base, info on manufacturers and machines produced, etc… and no membership is required to browse there.

Cheers,
Brad

PS: That diagram I posted is not specific to your motor (it's kind of generic), so I doubt the numbers will match with with what you have - just be aware as I would hat to see you burn up another motor!
 
#17 ·
Are you sure the bullet motor was 3450rpm? The bullet motors I've seen on Unisaws previously were all ~1725rpm with a drive pulley about twice the diameter of the driven pulley. Those windings do look a little crispy.
 
#18 · (Edited by Moderator)
Are you sure the bullet motor was 3450rpm? The bullet motors I ve seen on Unisaws previously were all ~1725rpm with a drive pulley about twice the diameter of the driven pulley. Those windings do look a little crispy.

- bigblockyeti
AFAIK, there was both 3450 and 1725 rpm bullet motors (as well as single and three phase), and you can tell the speed by how many brushes were used - 1725 rpm used four brushes, 3450 rpm ones used only two. Belt and pulley sizes were different depending on what was being used.

Unisaw Bullet Motor Repair
Unisaw Replacement Belts

Cheers,
Brad
 
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