electric motor problem

watchbill

"I recently bought an old table saw at an estate sale with a 3450 rpm 3/4 HP Atlas 110/220 motor with a 220 plug-in. I got it home, plugged it into my 220 air compressor outlet, and turned it on. It seems to run fine although taking a few seconds to get up to speed. Trying it out, the blade bogged down to a stop and I thought the belt was slipping, but then noticed the motor had stopped, although it seems fine without a load. I'm not at all familiar with electric motor wiring, but looking into it found an orange wire, brown wire, and black w/orange stripe wire connected together, then another black with orange stripe wire and a black wire connected and continuing to one side of the switch. There is also a green wire from the motor to the other side of the switch. Both black and green wires are switched and continue from the switch to the three prong plug-in. A white wire is grounded to the motor, then grounded to the saw at the switch box. The green wire goes from the switch to the left prong on the plug-in, the black wire goes from the switch to the lower center (frown shaped) prong, and the white wire goes to the prong on the right side of the plug-in. You'll immediately notice that I don't have a clue when it comes to drawing an electrical diagram, but hope someone can tell what I've got and what needs to be done. Thanks, Bill

Yoyizit

Measure the voltage across and the current through the motor under no load and under full load. It could be running on 1/4th power.

a7ecorsair

The first thing I see is the white wire which is connected to the motor frame is not connected to the ground pin on the plug. The U shaped pin is ground. Since it is a double pole switch, it will be switching the two hot leads and not the ground. Are you sure your diagram is correct?

humberguy

Yea, measure the current with load and no load. Also take off the belt from the motor and try to turn the shaft of the motor by hand. Check if you have difficulty trying to turn the shaft by hand. Maybe the motor is ceasing up, the bearing is going bad.

forresth

My thoughts too.

If your diagram is correct, the saw will shourd out if it touches a ground, you it will zap you if you touch it and a ground.

you'd also be only getting 1/2 voltage to the motor.

but you also said its a 120/240 motor. it might be hooked up on the motor side for 120, just wired in a messed up fasion to a 240 plug

watchbill

Yes, it's correct, and when I originally found the white wire bypassing the switch and not going to the ground pin on the plug as I thought it should, I figured I had better start asking some questions before making any changes, especially since I'm not familiar with this type of motor. So... would it be correct to remove the green wire from the switch, running the green directly to the plug and connecting it to the side opposite the black wire where the white wire was, then running the white wire through the switch and connecting it to the U shaped ground pin on the plug?
The motor spins freely by hand with the belt removed.

frenchelectrican

STOP AND DO NOT USE THIS UNTIL FIX FIRST!!

I am suprised that you did not get any serious electric shock from this one the way it conneted the white wire from the motor and that grounded to the table saw frame and I am suprised the breaker did not kick out on this if that is legit 240 volt circuit.

However can you get the motor manufacter nameplate I may have a chart for this one and normally green is used for ground purpose only but need to see the photo or get the motor model and wiring connection diagram to be on safe side.

The way you have drawen now if that motor is true 240 volt connection then you are running on 120 volts that why you don't have any toqure to get the motor running.

I will add more info along the way as soon I get the model number from you myself or one of the other members here will steer you in correct way with legit connections.

Merci,Marc

watchbill

Thanks Marc,

Well, I did get this awfully cheap at an estate sale, and they didn't tell me how the previous owner had died.... hopefully it wasn't while using the saw, but it does look like it's been this way for quite awhile. As soon as I looked into the wiring I had a feeling something wasn't right and won't be using it until it's sorted out. I'm at home right now and the saw is at a cabin we have about thirty miles from here, but I hope to go there within the next few days and I'll get the information from the motor and let you know.

Bill

frenchelectrican

That is wise move not to use it until it sorted out first for safety sake.

As soon you give us the model number we will go from there and one of us will make a correct drawing to hook up in safe manner.

Merci,Marc

watchbill

There is no wiring diagram on the motor, but it is an Atlas Super Power, and the ID plate shows it to be catalog # 2750, frame 1216B, serial number 4466HH04470. There is a scratch through the fourth number in the serial number, but as best I can tell, it is a 6.

Thanks again for your help, Bill

watchbill

Originally Posted by watchbill
"I recently bought an old table saw at an estate sale with a 3450 rpm 3/4 HP Atlas 110/220 motor with a 220 plug-in. I got it home, plugged it into my 220 air compressor outlet, and turned it on. It seems to run fine although taking a few seconds to get up to speed. Trying it out, the blade bogged down to a stop and I thought the belt was slipping, but then noticed the motor had stopped, although it seems fine without a load. I'm not at all familiar with electric motor wiring, but looking into it found an orange wire, brown wire, and black w/orange stripe wire connected together, then another black with orange stripe wire and a black wire connected and continuing to one side of the switch. There is also a green wire from the motor to the other side of the switch. Both black and green wires are switched and continue from the switch to the three prong plug-in. A white wire is grounded to the motor, then grounded to the saw at the switch box. The green wire goes from the switch to the left prong on the plug-in, the black wire goes from the switch to the lower center (frown shaped) prong, and the white wire goes to the prong on the right side of the plug-in. You'll immediately notice that I don't have a clue when it comes to drawing an electrical diagram, but hope someone can tell what I've got and what needs to be done. Thanks, Bill

STOP AND DO NOT USE THIS UNTIL FIX FIRST!!

I am suprised that you did not get any serious electric shock from this one the way it conneted the white wire from the motor and that grounded to the table saw frame and I am suprised the breaker did not kick out on this if that is legit 240 volt circuit.

However can you get the motor manufacter nameplate I may have a chart for this one and normally green is used for ground purpose only but need to see the photo or get the motor model and wiring connection diagram to be on safe side.

The way you have drawen now if that motor is true 240 volt connection then you are running on 120 volts that why you don't have any toqure to get the motor running.

I will add more info along the way as soon I get the model number from you myself or one of the other members here will steer you in correct way with legit connections.

Merci,Marc

Looking the wiring over again, It occurred to me that the plug is a standard hardware store replacement type, and whoever put this 'new' plug on the cord probably couldn't remember how the wires were originally attached and reversed the positions of the black wire and the white ground wire, so I disconnected these two wires from the plug, put the black wire where it belonged and the white wire on the ground terminal. I'm still a little leery about touching the saw, and won't until I'm sure everything is correct, but plugged it in, hit the switch, and it immediately started at full speed rather than taking a few seconds to build up speed as before.
So the white wire is still grounded to both the motor frame and the saw itself, but now continuing to the ground terminal of the plug, and the black and green wires still go through the double pole switch. Can I use this now or does something else need to be done?

frenchelectrican

The white wire on the motor where you see it grounded that should be insluating up due that white wire is allready a hot conductor due you say 240 volt set up.

Check the green wire at the motor junction box and you may have to get the DVM and read on ohm scale { with power off and unplugged of course } and read the ground pin { it should be green wire and the metal table saw frame or the motor frame itself you should have pretty low ohms reading { near zero } then check the white conductor as well do repeat the test to make sure it not crossed connection or grounding issue.

that should be proper once you test the green conductor to the frame it will read right but if open then you need to do little more checking on that.

Merci.
Marc

forresth

white can be used as a neutral, but Green should always be used as a ground.

of course this motor is probably older than those standards.

watchbill

Exactly what I found out! I finally decided to take this thing to a local electric motor shop and they thought the motor was from the early 1940's as none of their reference materials covered it, although a little detective work showed everything to be OK and they said basically the same thing about the green wire... there were no such standards when the motor was made.
Now I'm wondering.... could a non-contact voltage detector have shown me if the metal saw table was 'electrified' ?

Bill

a7ecorsair

A volt meter would work too - saw motor case to earth ground.
So, when you get it cleaned up and the blade sharpened, are you going to show us a picture?