Floor fan won't run?

Normally these things use a squirrel cage motor plus 2 series caps for speed reduction.

NT

Very sure this is stock and deffo only one cap.

It's one of these (not Clarke particularly).

Cheers, T i m

Assuming it doesn't have brushes, and your continuity tests included the switch, about the only thing you haven't excluded is shorted turns. And possibly capacitor breakdown at mains voltage, so it's worth trying the new one.

What's the voltage across the winding? Higher the better. If its nominally (230 - 206) then it suggests the winding is a resistor indicating a shorted turn somewhere. I'd like to see 100V or more.

These normally use a shaded pole motor. The rule of thumb for feed current via a capacitor is 80mA per uF. So you should have a maximum current below this. measure the current with a moving coli meter.IME if after stripping the motor and soaking the sintered bushes in an oil/parafin mix then reassembling, you are looking for a duff connection somewhere as your resistance reading seem reasonable. Good luck.

The OP has already measured the capacitor value to be 2uF. With 206V on speed '1' I would expect around 150mA and I guess would confirm that side is working.

There aren't many AC moving coil ammeters still around! I think we're talking clamp meter which is a lot less intrusive.

It doesn't Roger, an AC 'synchronous motor' I think they call them.

They did, and without (just in case). I also forgot to mention there was a sort circuit between neutral and one side of the run winding.

And I think that would be difficult without knowing the original resistance of the windings.

Check. It should be here on Monday. ;-)

Cheers, T i m

I don't think it can be. Sychronous motors lock to the mains frequency. Fan motors have slip.

someone needs a junkbox.

NT

I think I would call them shaded pole induction motor:

But who knows the economics of motors and control gear these days.

Now that's weird ... I just put the meter on it again to read the voltage across the run coil, powered it up and it started working!

However, it then slowed down again (below that of speed 1) so is it looking more like a bad run cap (given that the thing looks new and all the coils are a nice clean copper colour and seem to read reasonably)?

Cheers, T i m

Fan motors have slip.

Sure, I was probably just differentiating between a brushed and non-brushed motor. ;-(

'Someone' has more than enough 'junkboxes' but just none that holds that sort of component (more likely low voltage / digital stuff) or that I can find (hence my question about a box database a bit back). ;-(

Cheers, T i m

And you would probably be right. I forgot the key term I was thinking of was 'induction'.

In this case I'm sure it's a pretty cheap and simple induction motor (or some sort) and as you may have seen me mention elsewhere, just span up for a few seconds! Now, it was either the cap having another death spasm or there is an intermittent joint in the wiring somewhere (although it all seems pretty neat, clean and undisturbed).

If when I try the replacement cap and assuming it works, I'll give all the wiring a wiggle to make sure.

Cheers, T i m

Do measure the winding voltage too. It will give a clue to the inductance.

Just thought, since you measured capacitance can you also measure inductance? Though I doubt at 50Hz!

As I mentioned, I went to and it span up!

;-)

I need to make the connections safe again and run it up when I'm awake and if it doesn't actually work (or turn out to be a dry joint or some such), I'll see what the voltage is across the run winding. At one point I thought I saw ~12-14V (when it was ~206 across the cap) but when I went to recheck, it was working.

Cheers, T i m

These fans have always seemed a bit of a black art. I have one and it seems to be taking longer than it used to to get to any particular speed nowadays, though does not get very warm. I guess eventually things just tend to wear out but not looked inside while it still goes around. Brian

There does seem to be a fair selection of configurations that's for sure.

We have one on the wall in the kitchen and I think airborne grease gets into the bearings and makes them drag till the motor (and / or bearings) warm up.

I replaced the blade on mine (plastic went brittle and broke whilst being cleaned so replaced it with an ally one) but am due to try washing the bearings out and re-lubing them to see if that helps it start up quicker.

Cheers, T i m

Well, after a bit of a faff (cap didn't arrive) I ordered another from elsewhere, put it on and nothing. ;-(

The fan still 'hums' slightly when power is applied, like a coil is getting power but the motor not spinning?

The strange thing is previously, if the fan left (for say a couple of days) and you turned it back on again it would actually spin up ... but then slowly slow down and stop again.

Strange ...

Cheers, T i m

Have you stripped the fan and oiled the sintered bearings?

No, no need, the fan blade spins very freely and the whole thing looks like new?

Cheers, T i m