What's new
What's new

Motor problem

wawoodman

Hot Rolled
Joined
Jun 23, 2006
Location
Seattle, WA
Greetings, all.
I have a Delta Unisaw, 3 HP single phase 220v, magnetic switch. Yesterday, I tried to start the saw, but the motor wouldn't come up to speed. It seemed to "shudder" for about 5 seconds, and then tripped the breaker.
I have 220 at the receptacle. I plugged the saw into another 220 line, and it did the same thing. The 220 shaper runs fine.
Does this sound like a motor issue, or a switch? I'm thinking it's a relay in the mag switch, but as an electrician, I'm a damn good plumber, so I'm out of my depth here. Who should I call? Is this the sort of thing that an electricial would handle, or do I need a machine specialist?
Thanks,
Mike
 
You need to check first what kind of motor it is, if it is capacitor start (large capacitor mounted to the outside) then you may have either start winding problems or open centrifugal switch in the motor, if the motor is very high RPM, and you can see brushes then it is most likely a Universal motor, that fact that it is 1 phase, I would say you have a bad motor. Especially as usually there is nothing else connected to a saw except the blade!
Presumably its free to turn by hand?
M.
 
Before you go farther, verify that the blade will turn easily if you move it by hand. Normally, there should be almost no torque load on a circular saw motor when it starts up.

If the blade turns easily, I would look for a problem inside the motor, like a bad centrifugal switch or capacitor. You can remove the motor and take it to a motor repair shop. It might be cheaper to find a new motor on eBay than to hire an electrician.

Larry
 
Unisaw motor.

My guess is that saw dust has fouled the centrifugal starter winding switch or the starter cap has failed. Try blowing out the area at the rear of the shaft/motor. Grainger, Surplus Center or any motor supply house will have the needed capacitor. If you can't find one capacitor that is large enough you can wire two or more in parallel if needed. Remember to short across the capacitor contacts before handling them.

Larry on Lake Superior
 
If single phase, almost certaily a capacitor. Centrifugal switch a distant second. Easy to fix. R & R the capacitor. You can get a replacement if you take the existing dead cap and the motor name plate ratings to a local motor shop. Should cost $9 to $15 depending on mark-up.

If three phase, chances are there is an open phase. Check the magnetic starter and depress the "reset" button if there is one. There maybe a loose wire either in the starter or the motor's junction box.

Older Unisaws had repulsion induction motors but they are a rare beast now. This is an AC motor that operates as a series wound motor when starting (has brushes, commutator, and a wound armature). When up to pull-in speed, a shorting mechanism shorts the comm and it runs as an induction motor thereafter. Normally these motors are very reliable but when trouble hits, it's usually the comm shorting mechanism. R/I motors are a job for an ancient gray haired motor mechanic. Young farts haven;t the know-how.
 
I have a Delta Unisaw, 3 HP single phase 220v, magnetic switch. Yesterday, I tried to start the saw, but the motor wouldn't come up to speed. It seemed to "shudder" for about 5 seconds, and then tripped the breaker.
I have 220 at the receptacle. I plugged the saw into another 220 line, and it did the same thing. The 220 shaper runs fine.

Is your Unisaw a low voltage starter (LVC)? If so, I have the instruction sheet that came with mine along with the wiring diagram, if that will help you.
You can use the wiring diagram to check out the system.
It has been my experience that not all electricians understand a machine's starter, but the better ones do. Good luck........pg

UnisawLowVoltageStarterInfo001.jpg


UniSaw3phwiringdiagram.jpg





 
L Vanice[URL="http://cgi.ebay.com/NEW-Leeson-3-HP-Delta-UNISAW-Motor-3450-RPM-230V_W0QQitemZ230248507177QQihZ013QQcategoryZ26226QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247" said:
NameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247[/url]

Note that the Unisaw needs a custom motor with mounts welded to the housing, so you don't get to buy a cheap standard motor.

Larry
Larry is correct! The Unisaw uses a motor that is unique to a Rockwell/Delta Unisaw. There is no such thing as getting a standard NEMA frame motor as a replacement. If you need a motor, you have to purchase a Unisaw motor. Very expensive goes without saying..........pg
 
update

I pulled the capacitors and took them to the motor shop. They checked out fine. The fellow there said that starter windings (?) would be the next most likely culprits. So I'll drop the motor, and take it down to him. Damn. Those things are heavy.
 
Sorry i saw this post late. First and easy check would have been to remove cover on starter switch then use a piece of dry wood to close switch contacts. This will eliminate the coil etc as possible causes. While that box is open vacumn out the sawdust and look and the contacts. that siad most likely is the stater witch insid ethe motor or the start capacitor as people already said.
You can use a nema frame motor on the unisaw. I mounted one to fit. Simple enough. Mine is bolted to a to an iron plate about 3/16 thick roughly 6" square. Then some 2x2 or so angle is bolted to the plate with holes and slots cyt to match the unisaw mount.
Bill D.
Ps as long as it is open check the arbor bearings and drive belts. When I have to work on a motor and take the wiring off I like to put aplug on the mootr and a outlet off the box so I never again have to stand on my head when I replace/remove that motor.
 








 
Back
Top