Starting Single Phase Electric Motors

[silentC]

I went to the tip yesterday and salvaged the motors out of two driers and a washing machine. Two of them seem to start OK with just the main winding connected to the 240 but one of them needs a manual spin to get it going. Does anyone know how to wire these up so that they are self-starting? If I connect one of the other windings, the motor turns at a low speed, so perhaps I need a momentary switch on one of these or something?

[q9]

Sounds like you need a capacitor. Been done in these forums before, last year sometime. Search on "capacitor".

[craigb]

Darryn,

If you can get hold of the Tools and Shops magazine that is in the newsagents now, you will find on Page 96 a comprehensive article on how induction motors work.

It does seem like you need a new capacitor BTW.

[journeyman Mick]

Silent C,
The one that needed a manual spin to get started would have had a capacitor start. They generally start up on one one set of windings with the capacitor giving a bit of a boost and then when they get up to speed there's a set of spring loaded weights that fly out under centrifigul force to switch the power over to the running windings. At least, that's my understanding of how they work. The capacitor is a cylinder sized somewhere between a fat texta pen and a beer can. No doubt others less technically challenged than myself will be able to cast more light on the subject.

Mick

[Sturdee]

Darren,


You picked up 3 motors. Does that mean a new sharpening area with 3 newly built grinders or are you going to build other machines like a disk sander and drum sander etc.

Peter.

[silentC]

Peter,

I picked up as many as I could be bothered removing, hoping that at least one would work. It was a hot day and the flies were thick! I was very surpised to find that they all worked. I'll probably go back and get some more. I have heaps of things I want to make:

Grinder (like yours)
Drum Sander
Stationary Belt Sander
Gingery Metal Lathe
Shaper
Miller

etc...

I also picked up a big 8" squirrel cage blower out of a commercial air conditioner. I wanted it for the fan but the motor works as well, which is a bonus. Not sure how to work out the power rating on it though. All the electronics were intact but I had to bypass the relay switch to get it working. That's probably why it was discarded. A new relay and it'll be fine for my Cyclone...

[Sturdee]

Darren,

I know what you mean. I needed two motors and one timer switch so I picked up four dryers and all four motors and switches work perfectly. One of them is an exact copy of ours so that one went into underhouse storage for spare parts.

When I find some time I am going to use one for a large drumsander. I have a set of plans for that. If you want a photocopy pm me your address.

Peter.