Powermatic 75 blower motor issues - looking for motor advice.

[Phillip Mitchell]

My blower motor popped a 30 amp breaker on Friday afternoon and I noticed a suspicious electrical burning smell. Reset the breaker and tried the switch again and it was pretty weak / not moving air to start then sounded like it was “running away” going way over the normal speed. Killed the switch and pulled the motor out and this is what I found.

Im not a motor / electrical tech so maybe someone can tell me what I’m looking at. Windings look “crispy” and were extremely dusty. Also the end of the silver (aluminum) round part (rotor?) just outside the shaft had what looks like some broken tabs, but not totally sure.

I’m planning to call the motor shop in the morning and see what they say and likely take it to them if there’s a chance that they could repair.

What am I looking at and what are the chances of repair from a proper motor shop? Or would I be better off to ask them if they have any suitable replacements that could fit (fat chance?) as far as cost comparisons. If so, Is there any reason or logic in going with a bigger (5HP?) motor and keeping the same impeller or is that pointless / asking for trouble. The impeller is steel and 14” in diameter. I’ve been pretty happy with the performance of this setup and really am not in a place to want to replace the DC as I have a good bit invested into it as well at the location of the plumbing.

Not sure if this motor is proprietary or what, but most of my shop is down now because of this and time is of the essence to get back up and running ASAP to minimize lost production.

Early 90s era Powermatic 75 dust collector (I have it modified with 2 Wynn canister filters and a SDD XL before this machine.) 3 hp, 220V single phase.

Any thoughts? Thanks in advance.

[Kevin Jenness]

I'd let the motor shop diagnose it. With that much dust in the windings it's not surprising they look fried. Increasing the hp with the same impeller will be of no benefit.

[Jim Becker]

^^ This.

And once you have a solution for the motor, try to ascertain if you can reassemble things to avoid that kind of build-up. Was that an open motor? I would think that a sealed motor would be a better choice for this application.

[Bill Dufour]

Regarding the "fan" blades. I bet those were removed at the factory to balance the rotor once it was wound.
Bill D

[Russell Hayes]

I have the same blower. My OE motor is TEFC as should any DC motor. Should not have dust in it.

[Phillip Mitchell]

Thanks for the replies.

I took it in to the motor shop this morning and they took it apart on the bench while I was there and found shorted start and run windings on the other end of the motor than what pictured in the OP. One of the bearings is in poor shape. They quoted ~$500 to rewind, replace bearings, caps etc.

The mount as well as the shaft that connects to the impeller seems to be specific enough that I can’t just make an off the shelf motor work. I told them to go ahead and start working on it as it’s apparently a ~3 day process to rewind a motor. Aside from a 3 phase version for a PM 1900 (present day rough equivalent of this model) on an unfamiliar website for $600 plus shipping, I found no real options online for factory replacement motors. The motor shop will likely be using better bearings, caps, and the winding job will be higher quality than the factory job I would imagine, so hopefully that will work in my favor in terms of longevity and reliability.

The thought more than crossed my mind to use this as the opportunity to buy the ClearVue cyclone I was wanting when this Powermatic collector came along for next to nothing last year on the local C list, but that would be 6 times the price of the motor rewind and not get me up and running any quicker. Ceiling height limitations are also at play and I will save the cyclone upgrade for when I move out of this shop and there’s more height to work with.

The biggest pain with this type of issue is the shop downtime. A similar challenge was posed last summer when my rotary phase converter motor needed to come out and be repaired and most of the shop was basically dead for almost a week.

[Phillip Mitchell]

Regarding the dust, I was surprised as well as this is definitely a TEFC motor. The motor shop said they would do what they could upon reassembly (silicone certain seems, etc) to try and prevent that in the future but that they’ve seen that often even in sealed motors.

[Tom Bender]

Holy dust mites Batman, that's a lot of dust! Now I'm not sure anymore just what TEFC means. If I had that model motor in my shop I'd take it apart as a precaution.

You should send those pictures to Powermatic and ask how this might have happened and are their newer motors any better.

[Bill Dufour]

TEFC Means totally enclosed fan cooled. It does not mean air tight, water tite or rainproof. It also does not mean explosion proof.
Enclosed means closed off. It does not mean sealed. There are no gaskets on the endbells. May be one under the wiring box or not.
Bill D

[Phillip Mitchell]

Just to update - I got the motor back on Friday. Rewind, new bearings and capacitors for right at $500 and 3 days after I dropped it off. I re-installed it and it sounds great so far. I did mention about the dust; the tech said it wasn’t that uncommon to see dust like that especially in a dust collector motor and that he would do what he could to seal any connections with silicone when reassembling.