[Amps] Re: Shaded Pole Blower Motor

[Will Matney]

Hal,

I'm not sure but it could be the way that is designed. First, it's 
according to how thick the stack of lams is for the HP of the motor. 
Second, you mentioned them welding the lams together at six places. 
That's not good as this can set up eddy currents in the core. Eddy 
currents raise the reluctance in the steel like raising the resistance 
of a resistor. This in turn will make the core run hotter. Most all the 
shaded pole motors I've ever seen had one weld across the top of the 
core. The end bell bolts held the rest together as the bottom was held 
together by the bobbins tight fit. I cant see using six welds at all and 
I'm wondering if that was a manufacturing mistake of some sort. Maybe 
somebody ticked off at the company? It might pay to ask someone else 
about how their motor looks which uses a similar motor.

Will

Harold B. Mandel wrote:

>Dear Will,
>
>The Dayton 4C761 blower in the Commander 2500E amp
>has a coil DC resistance of 14 ohms. My Fluke 36 clamp
>a.c. ammeter does not register even one ampere draw
>when the motor is turning.
>
>The armature has a back-and-forth of around 0.050 inch
>and without a dial indicator and magnetic base I cannot
>determine if there is any run-out: I can't feel any, but there
>might be a couple of thou. I can see the oil film bulge when I
>rock the shaft left and right in the bronze sleeve.
>
>Grainger says that the motor can run in ambient temperature
>up to 104 F, and that's what the coil says. I thought it meant 
>the operating temperature of the motor, but after 20 minutes the frame
>of the motor is way, way hotter than 104 degrees.
>
>There are no ground-down wear spots on the armature or in the 
>shell. The copper pole windings look intact, and the laminations
>are welded on the periphery of the stack in six places that I can see.
>
>There's no discoloration of the nylon coil form and the armature spins
>freely when turned by hand, with no rough spots felt.
>
>In other words, the motor looks okay, feels okay, but just runs
>extremely hot.  Couple this with the fact of the motor failing to start
>when the amp is turned on, sometimes, not always, and it just seems to
>be a defective blower. Grainger wants about 40 bucks, shipped, for the
>whole shebang
>and I really don't feel like bothering Pat Stein at Commander Tech so
>I'll
>probably order up another one and scrap this piece.
>
>Thanks for the tips on S-P motors.
>
>Hal Mandel
>
>
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