Starter for Shaded Pole motor?

[JohnGeddes]

I have what I think is a mains-voltage shaded-pole motor (which looks a pig to remove and replace), which is sometimes not developing enough starting torque to get started. It sits and hums.

I've read that shaded-pole motors are simple but low-torque. Could I add a starter of some sort give a tiny extra "kick" that would provide the extra torque to get it started. I've done all the lubrication I can manage, and it does sometimes manage to start, so I don't think that I need to boost things by much.

The motor turns a 30cm long x 8cm diameter cylindrical fan in a "Kickspace" plinth heater in the kitchen (blows air over central heating pipes with fins).

 

[Diver300]

In a word, no. The core will be near saturation, so you can't increase the magnetic flux, which would increase the torque.

As the motor is driving a fan, it needs very little start torque, which is why they can get away with a shaded pole motor. If it had been designed with more start torque, it would be less efficient.

The very small start torque means that very little friction will prevent it from starting.

 

[BobW]

I've done all the lubrication I can manage, and it does sometimes manage to start...

This is fairly typical of shaded pole motors. Their torque doesn't decrease with age, but friction increases to the point where the motor will no longer start. The best solution is complete disassembly, cleaning and re-lubrication of the motor and fan. If the bearings are worn, then they need to be replaced. In other words, it's a mechanical problem, not an electrical one.

 

[crutschow]

Have you tried squirting some thin oil into the bearings such as WD-40 (available in the US, don't know where you live)? It's a very thin lubricant (almost like water) and it penetrates well to loosen up bearings with old oxidized oil. Such old oil can become almost like grease which adds a lot of start-up friction to the bearing.

 

[JohnGeddes]

Thanks to all. Have just applied WD-40 to everything I could get at, and it has done the job - for now at least.

John Geddes

 

[crutschow]

Glad the WD-40 worked for you (it's multi-purpose, also works well to remove store label adhesive).

A little later on, you might want to try adding some light motor oil (5-10w) to the bearings to provide a more long lasting lubrication.

 

[MikeMl]

Get some TriFlow at a bike shop. That stuff will not dry out like mineral oils.