Slip in Shaded Pole Motors

[George7941]

T1-R617 – ALLTEMP

www.alltemp.ca

The linked motor is a two pole motor, so its synchronous speed is 3600 rpm, yet its rated speed is 1900 rpm. That is a lot of slip with the rated speed at 53% of synchronous speed. Does this not lead to some inefficiency? Is this an instance where the motor designer had to have the 1900 rpm and could not get it with a 4 pole motor whose synchronous speed is 1600 rpm, so he went with a lot of slip?

 

[Dave9]

Being 208/230V rated, I'd wonder if also rated for 50Hz RPM but yes to me that seems like a lot of slip.

I could be wrong but doubt the inefficiency mattered as much to the (product it's embedded in) manufacturer as the low (to them in bulk, not the $45 as sold separately) cost, since shaded pole are as inefficient as it gets in the first place.

Does it matter? I mean if your heater-whatever needs a new motor and this is the drop in replacement, the inefficiency is turned into heat and (if) it's a heater, is contributing to the cause.

If you're considering this motor for a new project rather than a repair, I suspect you can find something similar elsewhere at lower cost as a *generic* (multi-application) motor rather than in the appliance repair parts seller genre.

 

[George7941]

You are right about the inefficiency not mattering in this application ( 240V wall mounted convection heater)

 

[Dave9]

Besides the inefficiency (in non-heater applications) my other gripe with average grade shaded pole motors is the typical, low lifespan of the bearings.

However long it took yours to wear out, in about 70% of that time on the new motor, I'd pull it and lube the bearings, should have a felt lined cavity to fill at both ends, may require taking the bolted on bearing caps off to get to them. I might even top off lube before installing the new one, just not enough for it to run out and make a mess.

 

[George7941]

I did this for a customer, so I do not have access to the motor for reoiling. When it wears out, he will call me and I will replace the motor with a new one.

Would have been nice if these small motors came with sealed ball bearings but they don't.

 

[Dave9]

^ There are exceptions but often the next most cost effective solution to longer life is move to a PSC type motor with larger bearings, even if still sleeve they tend to have larger bearings/bushings and oil reservoir cavities in addition to being more efficient. It's harder to make a clear cost:benefit comparison in today's market where things from China have floored the cost and made quality highly variable.

All I can say for sure is that free time to maintain and a few drops of oil are often less painful than the other alternatives.