burnt up motor?

[keith ouellette]

Hi;
It has been about a year since my last post and I have not been in my shop since due to illness and have not really finished setting things up. I have just recently felt well enough to start working again and started building some shelves and things for the shop. Everything has sat idle for about a full year.

Now to the important part: I noticed a burnt ozone smell and found my dust collector was not working. it was a 1 1/2 hp jet with the paper filter and I had it hooked up to run 220. I started to take the motor apart and found that the large coil of coper wire around the armature was burnt and some of the strands were melted. I had the motor and fan housing mounted on a shelf above the collection bag and filter and had 4" duct run around the shop ceiling (about 10' high) and then down to the machines.

Any idea how this could have happened? I didn't have that many hours on it.

[David Romano]

It's possible that the motor was wired for 220 and that you have the right breaker for it but that you accidently wired the receptical wrong. If you used 1 hot and 2 neutral, it is effectively 110 volt and the high current draw would overheat the motor.

David

[Rod Sheridan]

Hi Keith, assuming that you had the motor correctly wired for 240 Volts, and the motor wasn't overloaded, you may have experienced a random motor failure.

The insulation on the magnet wire may have had a pinhole, the wire could have rubbed on a lamination etc.

The start switch could have stuck closed and burned out the start winding, or the switch could have stuck open and burned out the run winding.

Regards, Rod.

[Mike Henderson]

If the motor was not enclosed in such a way that air couldn't get to it, which would cause it to overheat, or overloaded, I agree with Rod that it was probably a random failure.

This assumes the motor was correctly wired for 240V and 240V was properly supplied.

Mike

[keith ouellette]

I only have one hot and one neutral at the receptical and both of them attach to the breaker.

Is a 220 breaker supposed to be attached to both poles? thats the way mine is. The 220 breaker is shifted down one slot so it can connect to the left and right pole at the same time. is that correct?

[keith ouellette]

If the motor was not enclosed in such a way that air couldn't get to it, which would cause it to overheat, or overloaded, I agree with Rod that it was probably a random failure.

This assumes the motor was correctly wired for 240V and 240V was properly supplied.

Mike

The motor is in a closet of sorts. its about 4x4 and has at least 8' of ceiling. would being in an enclosure of that size cause it to over heat?

[keith ouellette]

Hi Keith, assuming that you had the motor correctly wired for 240 Volts, and the motor wasn't overloaded, you may have experienced a random motor failure.

The insulation on the magnet wire may have had a pinhole, the wire could have rubbed on a lamination etc.

The start switch could have stuck closed and burned out the start winding, or the switch could have stuck open and burned out the run winding.

Regards, Rod.

What could have over loaded the motor? It is attached to 4" duct and the motor and fan is at about 8' high and the ducts run at the ceiling and down to the machines. there is a blast gate at each machine. is pulling the chips/dust up to the ceiling causing the motor to be overloaded?

[David Romano]

I only have one hot and one neutral at the receptical and both of them attach to the breaker.

Is a 220 breaker supposed to be attached to both poles? thats the way mine is. The 220 breaker is shifted down one slot so it can connect to the left and right pole at the same time. is that correct?

The 220 should have 2 hots (110 x 2) and 1 ground. Sometimes 220 circuits have 2 hots, 1 neutral and 1 ground, but usually not. The plug will tell you. If it has 3 prongs, it is 2 hots, 1 ground. So you probably have 12/2 Romex, which icludes the ground wire. The black and white are both connected to the hots at the breaker, the ground to the ground. If you have 12/3 Romex and have a 3 prong plug, terminate the white on both ends and use the red and black for hots.


David

[keith ouellette]

The 220 should have 2 hots (110 x 2) and 1 ground. Sometimes 220 circuits have 2 hots, 1 neutral and 1 ground, but usually not. The plug will tell you. If it has 3 prongs, it is 2 hots, 1 ground. So you probably have 12/2 Romex, which icludes the ground wire. The black and white are both connected to the hots at the breaker, the ground to the ground. If you have 12/3 Romex and have a 3 prong plug, terminate the white on both ends and use the red and black for hots.


David

Thats the way its hooked up so it wasn't an electrical problem from the receptical end. Could it be a problem from the breaker box. both the white and black were hooked up to the breaker. could the breaker be positioned wrong so it was only delivering 120?

[David Romano]

Thats the way its hooked up so it wasn't an electrical problem from the receptical end. Could it be a problem from the breaker box. both the white and black were hooked up to the breaker. could the breaker be positioned wrong so it was only delivering 120?

The breaker should look like 2 regular breakers connected together with one throw switch. I imagine that it is a 20 amp breaker. I doubt that it could be installed on the bus incorrectly, but it's worth a look. Basically, it just takes up to slots on the bus, tough to do it wrong. Each half of the 220 breaker has it's own hot connection. Connect your black and white (hots) to these, and your ground to the ground bar. Notice that with most of the breakers, 110v, that the black is the hot and the white is connected to the ground bar, along with the bare ground wire. With 220v, the white is the second hot.

david

[Charles Lent]

I think your centrifical start switch (inside the motor) failed, keeping the current flowing to the start winding for too long. Whenever you haven't used a single phase induction motor for an extended period of time you should watch and listen to the motor and be prepared to shut it off if it makes any unusual sounds as it starts. A stuck centrifical switch or a defective capacitor will cause a loud sharp pitched whirring sound that's very distinctly different from the motor's normal running sound. If you can turn off the power to the motor within a few seconds of hearing this you will have saved the motor. Then you need to dis-assemble it and free up the centrifical switch mechanism and/or replace the capacitor, if it has one.

In your case, the motor was left on and the start winding toasted. Very large motors can be economically re-wound at local motor shops, but it's usually not economical to do common motors of less than 3 hp. If the motor has a special frame type they are usually hard to find and much more expensive to buy. These then become candidates for re-winding.

Take your motor to an electric motor shop and let them tell you what is the most economical route for you to follow from here. Estimates and a price quote for a new motor are usually free.

Charley

[Mike Henderson]

It's pretty unusual for a centrifugal switch to stick closed. My experience has been that they usually fail when dust gets into the motor and then the contacts won't close. In that case, the motor won't start. But I suppose it's possible to have a switch that won't open.

In most cases, it's much less expensive to buy a new motor than to get an old motor re-wound (especially small motors). Look on eBay - you can occasionally find really good deals there. I bought a new 2HP TEFC on eBay for about $125 shipped to me. I've been using it for a number of years now and it's going fine.

Re-winding is of most value when the motor has some special mounting and you can't find a replacement, or the replacement is extremely expensive. Your motor is probably a 56 frame (one of the most common).

Mike

[keith ouellette]

I think your centrifical start switch (inside the motor) failed, keeping the current flowing to the start winding for too long. Whenever you haven't used a single phase induction motor for an extended period of time you should watch and listen to the motor and be prepared to shut it off if it makes any unusual sounds as it starts. A stuck centrifical switch or a defective capacitor will cause a loud sharp pitched whirring sound that's very distinctly different from the motor's normal running sound. If you can turn off the power to the motor within a few seconds of hearing this you will have saved the motor. Then you need to dis-assemble it and free up the centrifical switch mechanism and/or replace the capacitor, if it has one.

In your case, the motor was left on and the start winding toasted. Very large motors can be economically re-wound at local motor shops, but it's usually not economical to do common motors of less than 3 hp. If the motor has a special frame type they are usually hard to find and much more expensive to buy. These then become candidates for re-winding.

Take your motor to an electric motor shop and let them tell you what is the most economical route for you to follow from here. Estimates and a price quote for a new motor are usually free.

Charley

I wish I would have posted this before I threw it out with the trash. I never knew they could be re wound.

[Tom Veatch]

... could the breaker be positioned wrong so it was only delivering 120?

Not if it's a double pole breaker and the circuit conductors are both connected to the breaker. There are some boxes that require the breakers to be in certain positions to provide 240v, but if putting them in the wrong position supplies zero voltage, not 120.

[Rod Sheridan]

What could have over loaded the motor? It is attached to 4" duct and the motor and fan is at about 8' high and the ducts run at the ceiling and down to the machines. there is a blast gate at each machine. is pulling the chips/dust up to the ceiling causing the motor to be overloaded?

No Keith, it could only be overloaded by having too much airflow through the collector, such as running it without bags or filters.

Enclosing the collector in a closet wouldn't cause it to overheat, since the collector would be exhausting hundreds of CFM of air flow from the closet. That's far more than a small motor would require for ventilation.

Your motor wasn't worth rewinding, unless the frame is something special. The last analysis I did on small motor rewind costs at work, was that less than 10 HP wasn't worth rewinding unless it was a premium or special frame motor.

Check your motor connections when you buy a replacement collector to make sure it's wired correctly, and measure the voltage at the receptacle to make sure it's correct.

When a motor fails due to overheating, normally the signs of damage are spread out over the entire winding, burned and discoloured insulation etc. It sounds like your motor had localised damage, which often indicates a fault to ground such as pinhole/abrasion etc.

Regards, Rod.