Growly, slow three phase motor, but resistance of windings is consistent

[Just a Sparky]

OP has access to commercial three phase power. That will be a far more definitive test than anything else. It will either run, hum or throw sparks.

 

[JST]

Yep, that will tell.

 

[JasonPAtkins]

Ok all, I appreciate your feedback. You're right that I don't care about the RPC, lol.

I tested the machine on grid three phase, and my results are (to my way of thinking) inconclusive.

Here's the machine in question, a Boyce-Crane 8" jointer (fencing and knives removed):

Observations arguing in favor of a good motor:
-It does get up to speed relatively quickly, considering the inertia of the integral cutterhead
-It is a 1.5hp motor whose dataplate says 2A draw at high voltage. After the initial inrush, the amperage of all three legs settled in around 1.3A. This seems reasonable considering it wasn't cutting anything, but was still spinning a heavy-ish head.
-I ran it for a total of less than 4 minutes, but the bearings are not warm.
-Upon turning it off and disconnecting, I felt inside the back of the motor and touched the back of the windings all around. None of them were warm.

Observations arguing for something being wrong with the motor:
-I feel like I can see smoke coming out of it, but I suppose it could just be dust from sitting
-One specific side of the motor housing is getting pretty warm much faster than the rest of the motor. It's this side:

Another observation, although I can't categorize this because it may be normal. I've never been around a motor with no rear bearing, so I've never had occasion to observe this. The spinning part (is that called the armature?) is by far the hottest part of the motor. Is that the part that should be getting hottest? It's the part my finger is touching in the below pic.

Furthermore, I recorded video of the motor starting up twice so everyone can chime in. Does this sound and seem normal, can I trust my equal and reasonable amp readings on the three legs, and start using the tool? Or does some information here make you think I should be sending the pulleys to ditch this integral motor and convert the machine to a pulley drive that can use any spare motor I have lying around?

Startup #1: https://photos.app.goo.gl/XrAgv4dTrtYjFFQq6
Startup #2 (note what smelled like smoke, not sawdust, coming out of the back at the beginning: https://photos.app.goo.gl/kWKzAEiZ3CiUEAaF6

What say you?

 

[JasonPAtkins]

As I think this over, I'm wondering if the armature isn't rubbing a little against the core on that one side that's warming up. The motor bolts to the frame of the machine with three bolts and two alignment roll pins. They're in correctly, but if there is somehow some other misalignment between the two bearings, one inside the motor housing, and the other at the other end of the cutterhead in the frame of the machine, that would explain a lot. Perhaps some smoke, definitely the spinning part getting hot, and also the heat on the motor housing, on the side where it's rubbing.

 

[sfriedberg]

It doesn't sound very happy, but I can't point a finger and say "that's the specific cause". Can your guys in Africa do the conversion if the current motor craps out? If so, I'd leave the current motor as-is, but send the pulleys anyway.

 

[johansen]

Is it 1.3 amps on all 3 phases?

If not, there is your problem. It does not sound happy. Could it be saturated and connected in a zig zag pattern? If so half the windings are shifted and it would rather run on 277v instead of 480.

However, in contrast to my speciation I will say I intentionally reconnected a 2hp 3500rpm motor for 138v double delta instead of 240v Y (so I could get more hp and torque from a 240v vfd)

Running on 208v 3 phase it drew 17 amps no load (I was surprised it was saturated that bad).. however it had zero shortage of starting torque and seemed to start and reach 3500rpm in well under 1 second.

Yours doesn't come close. But the low line amps are telling. I like to use a watt meter for these kinds of trouble shooting problems.

 

[Just a Sparky]

Looks like a 40's or 50's Century motor.

Did you measure current on all three phases? Would be interested in seeing the locked rotor currents on all three.

Motor should not be emitting smoke. The fact that it emits smoke during startup, yet the windings remain cool to the touch does not add up. We are missing information.

Also, your images failed to embed. Try again please.

 

[JasonPAtkins]

Yes, current measures the same on all three phases.

 

[swarfless]

Standard check for poling (rotor rubbing on stator) is take rotor out & paint cylindrical surface with mark-up stain. Reassemble motor & run briefly. Remove rotor & inspect for bright metal patch/patches, & inspect stator for transferred blue (or whatever colour mark-up stain you use). Painting the rotor in such a way used to be standard post-rewind practice where I come from, as an aid to future diagnosis.

 

[rons]

If it is rubbing the surfaces would already be shinny.

 

[MwTech Inc]

Start up is about right compared to my Yates 12" jointer. witch has the same style of motor setup
You do have bearing whine....
With current the same I'd say you are good.
Was not smoke..lol dust.

 

[JasonPAtkins]

Excellent info, thanks all. I'll send a new set of bearings and then once it's in Africa pull it apart to see if it's rubbing. I suppose rubbing could be caused by sloppy bearings, or could be that the keying between the motor and jointer is somehow bent. Thanks!

 

[MwTech Inc]

Jason
hop over to owwm.org and pose the question about bearing changing......don't want any surprises once it leaves usa