Table saw motor keeps tripping - Woodworking Talk - Woodworkers Forum
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General Woodworking Discussion > Table saw motor keeps tripping
Danno6102 10:50 PM 08-12-2010
Just got a used Jet 10" contractor saw (JWTS-10JF) off craigslist & I'm going through it right now aligning & tightening things. I have had some intermittent trouble with the motor tripping (the reset button on the motor itself) when I stop & then restart the saw right away. Was more of an annoyance. Last night I aligned the pulleys, looked like they were off to me. I go to start the saw to cut some test dado's with the new dado set I bought & the motor trips every stinking time now. It'll start to spin, then trip.

I can spin the pulley, belt & blade fairly easily. Is this a start cap that is going bad? Any easy tests I can do to figure out what's wrong with it?

Thanks,
Dan

knotscott 11:15 PM 08-12-2010
Have you tried the saw on a different circuit to rule out the breaker? I'd also try the motor with the belt off.
Itchy Brother's Avatar Itchy Brother 11:23 PM 08-12-2010
Do the tests mentioned.Is the power cord frayed?
rrbrown 03:07 AM 08-13-2010
Quote:
Originally Posted by Danno6102 View Post
Just got a used Jet 10" contractor saw (JWTS-10JF) off craigslist & I'm going through it right now aligning & tightening things. I have had some intermittent trouble with the motor tripping (the reset button on the motor itself) when I stop & then restart the saw right away. Was more of an annoyance. Last night I aligned the pulleys, looked like they were off to me. I go to start the saw to cut some test dado's with the new dado set I bought & the motor trips every stinking time now. It'll start to spin, then trip.

I can spin the pulley, belt & blade fairly easily. Is this a start cap that is going bad? Any easy tests I can do to figure out what's wrong with it?

Thanks,
Dan
Dan I'm not sure about that model or it's age but does it say made in china on the motor? It probably does. Does it trip a second or 2 after you try to start it? Probably. It could be straining because of misalignment which you said you just completed or a bad bearing or two but you said it spins fairly easy. Take the belt off so there is no load on the motor and try turning it on. If the motor trips it could be a bad overload switch or a bad centrifugal switch but more likely a short in the windings. You would have to take the motor partially apart to check for a short but A quick test would be smell the motor if it smells burnt it's shorted. However mine didn't smell but was shorted. If the motor says Made in China you probably will be looking for a new motor. Less likely is it says made in USA or maybe Taiwan which you may be able to have a electric motor shop rewind it. I know they will rewind for USA but not sure about Taiwan and definitely not China.

If the start capacitor was bad it wouldn't start or would drag. If the overload switch is bad it's tripping for no reason and if the start and run windings are making contact (shorted) then your getting power from the start capacitor when your not supposed to and it trips the overload switch.
rrbrown 03:11 AM 08-13-2010
Quote:
Originally Posted by knotscott View Post
Have you tried the saw on a different circuit to rule out the breaker? I'd also try the motor with the belt off.
Quote:
Originally Posted by Itchy Brother View Post
Do the tests mentioned.Is the power cord frayed?
If it was tripping the breaker in the service panel it could be either of the things you suggested but since its the overload switch on the motor its more likely a short in the windings or even a bad overload switch. I seen this before unfortunately.
Danno6102 07:19 AM 08-13-2010
never thought about trying it with the belt off. I'll try that tonight & see what happens. So if it trips, we've narrowed it to windings or overload switch & ruled out misalignment. Is the overload switch easily replaceable?

Power cord is good. It is the switch on the motor that pops. So far the breaker in the service panels has not tripped.

It's only 3 years old & the guy said he didn't use it much. He's a contractor & bought it to use on job sites. Needless to say this saw isn't very portable, so it just sat in his shop most of the time.
robertd 09:24 AM 08-13-2010
Sounds like to me the start capacitors are bad. If they do not hold a charge for the startup the motor will pull what it needs to start from the line voltage and the amount of amps will spike to way over the breaker limit. My work shop compressor was doing the same thing and it was drawing 60 amps on startup.

Bob D
rrbrown 12:39 PM 08-13-2010
Quote:
Originally Posted by Danno6102 View Post
never thought about trying it with the belt off. I'll try that tonight & see what happens. So if it trips, we've narrowed it to windings or overload switch & ruled out misalignment. Is the overload switch easily replaceable?

Power cord is good. It is the switch on the motor that pops. So far the breaker in the service panels has not tripped.

It's only 3 years old & the guy said he didn't use it much. He's a contractor & bought it to use on job sites.
Needless to say this saw isn't very portable, so it just sat in his shop most of the time.

Yes that witch is pretty easy to replace but take a whiff and see if you smell a burnt smell first.

The age of the saw makes it very likely that its a China motor if your lucky a Taiwan made motor. Unfortunately it dont have to be used much to have a winding problem especially for China made motors. The don't use as good of an insulator on the wire when winding and it either wears off or has voids that cause problems.

Quote:
Originally Posted by robertd View Post
Sounds like to me the start capacitors are bad. If they do not hold a charge for the startup the motor will pull what it needs to start from the line voltage and the amount of amps will spike to way over the breaker limit. My work shop compressor was doing the same thing and it was drawing 60 amps on startup.

Bob D

I don't believe it's the start capacitor because if it was it would wind or slow start then trip. If it starts fast and immediately trips then the start capacitors are most likely good.

I could be wrong but I don't think so.

Danno6102 09:31 PM 08-13-2010
ok. here's what i found out tonight.

Motor = Taiwan

Both pulleys spin freely.

Belt off = no trip, runs fine

Belt on, no blade = no trip, runs fine

single normal blade = trip occassionally

3/4" dado blade = trip every time

I bypassed the button on the motor & everything was fine. it started every time. So my question is, what damage could come of bypassing this switch on the motor permanently?
woodnthings's Avatar woodnthings 09:48 PM 08-13-2010
Permanent Damage. Somethin ain't right here. Best to have it fixed, probaly just the thermal overload switch...could be loaded with dust, heats up and cuts out when hot. Blow it out first real good.
Switches are cheaper than motors. bill
rrbrown 10:53 PM 08-13-2010
Replace the switch probably just a couple bucks at most. The Taiwan motor is a good thing. You don't find USA motors anymore.
woody woodturner's Avatar woody woodturner 09:20 AM 08-14-2010
its triping under load sounds like the overload contactor is faulty
sjhanksaz 08:58 PM 01-18-2011
Quote:
Originally Posted by rrbrown View Post
Replace the switch probably just a couple bucks at most. The Taiwan motor is a good thing. You don't find USA motors anymore.
I have the same Taiwan motor on mine. My trouble is when I hit the start button on my jet saw. The motor hums and then the thermo breaker trips. I year or two ago I had a local shop check the motor and they put a new capacitor in it.

Well it still has the problem.

The only way to start the thing is to lift the motor up slightly then hit the on button and pray. Half the time (getting worse) it starts up. Then I lower the motor and the saw is just fine until I turn it off, then I have to do it all over again. My belt is not pinching anything. Blade and all spins nice, The motor just doesn't kick over.

If it's a new thermo button where can I buy a new one?

I am running 110 v right now. Will 220 solve my problems and make me want to use the saw instead of sell it.

Thanks
JohnK007's Avatar JohnK007 09:31 PM 01-18-2011
I'm thinking along the lines of Bob D. The capacitor. I'd start there.
knotscott 10:24 PM 01-18-2011
Quote:
Originally Posted by JohnK007 View Post
I'm thinking along the lines of Bob D. The capacitor. I'd start there.
I was thinking the same thing....if so, it should be < $10, and is a 5 minute installation.
mikkeeh 11:47 AM 01-22-2012
I just bought the same model saw. The first few times it ran fine....then would trip the breaker (on a separate 20A circuit). The thermal reset on the motor was damaged when i got it. Looks like something was dropped on it. I have not replaced it as of yet. I just changed the belt to a anti vibration link belt. Now it trips the breaker 1 out of six starts. Reset the breaker....and it starts ok for 2 or 3 or 4 time...then trips again.
johnnie52's Avatar johnnie52 12:51 PM 01-22-2012
I have to agree that its a bad capacitor. That will cause the kind problems you're having.
HowardAcheson 02:21 PM 01-22-2012
One thing to keep in mind is that it will draw more amperage on start-up with dado attached. The motor needs to overcome more inertia with heavier dado. It may easily run without a blade attached but have an intermittent overload with a blade and any immediate overload with a dado.
mikkeeh 12:31 PM 02-22-2012
FWIW: I found that my Jet saw would trip the breaker in the circuit box almost every time when the saw sat overnight in an unheated shop. I replaced the motor...Same problem. I replaced the breaker with a different brand. Was using Homeline by Square D......switched to Seimens.....problem solved. I also had another circuit that would periodically nuisance trip. Changed that breaker..problem solved. Seems Homeline breaker are prone to nuisance tripping when used for motors........interesting
Cliff's Avatar Cliff 03:34 PM 02-22-2012
Quote:
I have to agree that its a bad capacitor. That will cause the kind problems you're having.
Why? Because it's causing too much inrush?
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