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Steve Steven
12-03-2005, 06:15 PM
I have a problem with the motor on my Van Norman mill. I bought the mill without a motor, and fitted a 1HP Rockwell 1750RPM motor from a drill press to it. The motor is a 110/220 capacitor start motor, and leads correspond to the system in Grant Erwins piece http://www.metalwebnews.com/howto/elec-mtr/elec-mtr.html on electric motors.

It died on me, just did a "bump" and thats it, no hum, no noise at all. When energised, nothing.

I disassembled the wiring, and cannot get any good readings on ohmage of either the start or run windings. Using a Simpson 77 meter, I get 0.00 ohms on both, using a cheap analog meter I get 0 also. I do not have any leaks to ground, the capacitor looks OK, and there is no burned smell on anything. I have checked and I have power to the electrical box when the start switch is pushed (manual starter).

I am stumped, should I get a new motor, or is there somthing I am overlooking?

Steve

Mike Gibson
12-03-2005, 08:24 PM
Steve,
I know there are knowledgeable people on the subject of your question on this board.
I am not one of them. I wish I could help.

Maybe my posting this reply will cause those who are able to help to read this to see what I told you. Good luck

darryl
12-03-2005, 09:29 PM
You say you get 0 ohms on each winding- that says they're good. They do have some resistance, but very low, so a 0 reading, while not accurate, is a good enough indication that the windings aren't burnt out. I'd say there's a thermal breaker in there somewhere that is shot. If you get no hum whatsoever, and the voltage is coming to the motor, and the windings are good, you'll get some noise. Hum, rather. If no hum, the juice isn't making it past a certain point. Either winding if energized will hum, so even if say a start cap is shot, you should still get a hum from the run winding. If the start switch is shot, same deal, the run winding should hum. If no hum at all, there's a break in the flow somewhere. Back to the thermal breaker, or the overload breaker if it has one. This is the general idea, I don't know that particular motor.

Steve Steven
12-03-2005, 11:24 PM
Dayrrl,
There is no overload in this motor, and the circuit breaker is not popped. I was expecting a small resistanc, say 1 to 3 ohms, but am not finding it. On the other hand, if the windings are really 0 resistance, wouldn't it overload the breaker and pop it? I just don't know what is going on.

Steve

J Tiers
12-04-2005, 12:05 AM
It seems that the voltage cannot be making it to and through the motor.

Ad Darryl said, the windings seem to be good from the readings.

As you surmised, if the windings were truly shorted (both!) you would trip an overload breaker somewhere.

So, there is almost surely a bad switch, loose wire, etc, etc. somewhere. I am afraid its up to you to find it.

My first move would be to pull the plug, get my ohmmeter, and read across the hot and neutral pins on teh plug. Flip the power switch, and see if there is any conduction.

Since you almost certainly have contactors etc, there may not be, depending on whether it has transformer isolated control circuits or not. If you get some conduction either with switch off or on, assume power is getting into the unit, which you already said you believe you have....

Then, determine if your control box has a contactor or is a direct switch.

You can determine a lot by opening the box, and watching to see if the contactor closes when you "start" the motor...

if not, the coil is a supect, and you need to determine if power is reaching the coil.

If that is OK measure the contactor coil resistance, and see if it is open. If so, there's your problem.

If contactor closes, it must be open in the power wires thru the contactor, before it, or on the motor side. Some voltage measurements can determine what is up.

If you have a simple switch, its easy to check, (but I'd consider changing that to a contactor, as it isn't safe if power goes off.)

Since I don't know your wiring in detail, the above is pretty much an example. You'll have to figure out any differences.

Yes, you'll have to have the control box open and poke the voltmeter leads in and among the "hot stuff". If you don't feel comfortable doing that, get an electrically savvy person to help you, possibly an electrician familiar with motor controls. Better paying for that than messing up and getting a shock etc.

[This message has been edited by J Tiers (edited 12-03-2005).]

darryl
12-04-2005, 12:26 AM
Steve, you said 0 ohms, I'm going with that. I hope you didn't mean infinite ohms, as in open circuit.

You said the start switch is separate from the motor. If you read ac voltage to the start switch, and to the run winding, and the windings are good, then the break in the circuit could be in the neutral return lead from the motor to the electrical box where the switch or switches are located, and where line power comes in.

I might be missing something- do you have a main switch, plus a momentary start switch- wired in the same box?

Where are you putting the leads from the meter when measuring volts? If you put the black lead to the metal case of the electrical box, and the other lead checks voltages going to the start switch and probably the run switch or run winding, then you could see voltage there and not have the motor run. According to the wiring diagram that you posted a link to, there's two ways to hook it up to run. Are you using 110 or 220? You should be able to read ac voltage at the line 1 and line 2 terminals at the motor, with the main power switch on. Forget the start winding for now. If you have voltage across those two wires, then you're likely missing the connection between wires 2,5, and 3, as in fig 1- wires 2,8, and 3 if wired as in fig 2- wires 2,5 and 3 if fig 3- and 2,8, and 3 if wired as in fig 4. In each of these cases, those wires must be connected together, even though they may or may not be connected to line 2 wire coming in from the electrical box.

It happens often enough that wires don't get connected, even if a marette is twisted on. You can have a firmly attached marette and have a third wire which just doesn't get the connection inside it. If you pulled that wire, it might just come right out, or it might just make the connection and things will work again.

Steve Steven
12-04-2005, 02:40 AM
Guys,
I'm sorry, I didn't give a full description of the system. I am wired for 220V operation, using a three-wire connection (two hots and a ground) to a separate 220V circuit. The starter is a MANUAL SWITCH rated for 3HP at 220V, motor is 1HP. There is a manual reversing switch mounted on the cover to the motor junction box, it is a DPDT with center off. I don't know the rating for it, but it isn't switched under load and should be good.

I just replaced the motor start switch with a spare, when the problem first happened I thought it was the start switch since it has not been working normaly for the last few years. (mushy action, no snap to it) The motor has been working for ten years, with VERY low usage, there are times when it isn't turned on for weeks at a time.

After replacing the start switch and finding it still didn't work, I opened up the motor junction box. I pushed the start button, and read 120V to ground from both hot leads. I didn't check across both hots to check for 220V, tho.

I then made a sketch of the wiring connections, and took everything apart except for the wiring to the reversing switch. Thats when I measured the 1-2, 3-4, & 5-8 resistance (I had to go to the wire on the capacitor to get a good reading).

J Tiers, your statement "My first move would be to pull the plug, get my ohmmeter, and read across the hot and neutral pins on teh plug. Flip the power switch, and see if there is any conduction." sound like a good idea, I'll try it. Since I have manual switch, I should be able to get a good reading of the motor. I'll have to wire everything back up first.

Darryl, you asked "I might be missing something- do you have a main switch, plus a momentary start switch- wired in the same box?" The answer is I have a manual switch (on - off) on the side of the machine, and then a three conductor wire goes to the motor junction box, two hots and a ground, no neutral. Thats where the reversing switch is located.

You also asked "Are you using 110 or 220? You should be able to read ac voltage at the line 1 and line 2 terminals at the motor, with the main power switch on. Forget the start winding for now. If you have voltage across those two wires, then you're likely missing the connection between wires 2,5, and 3, as in fig 1- wires 2,8, and 3 if wired as in fig 2- wires 2,5 and 3 if fig 3- and 2,8, and 3 if wired as in fig 4. In each of these cases, those wires must be connected together, even though they may or may not be connected to line 2 wire coming in from the electrical box. " I think that might be the problem, I havent checked the reversing switch and thats where the 3,5 &8 wires all converge. I looks OK, however. I'll take it out of the circuit and wire it up without the reversing switch and try it again.

Thanks for all your help, It sure helps to discuss this with someone else.

Steve

Steve Steven
12-04-2005, 02:47 PM
Problem Solved!

Turned out to be a "people problem", I had not hooked up a wire in the start switch when I installed it.

I found out a lot of things, tho. My FLUKE 77 Meter (not simpson as I stated erronously) turns out to not be auto-ranging, you have to push the button in the switch to get it to switch from one range to the next, it was set for megohms when I was using it, thats why I was getting 0.00 ohms.

I found the problem when I tried J Tiers' suggestion to check from the plug thru the motor, no continuity. Opened up the switch box to check from there, found a wire dangling un-hooked up. DUH!

Thanks for the help, Guys, it is much appreciated.

Steve