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Floor fan won't run?

Hi all,

I've been given one of those big chrome floor standing 3 speed fans to look at because it doesn't run. It was given to my mate (not running) so I don't have any information beyond that.

When you power it up you can hear/ feel the thing 'humming' slightly, suggesting it is receiving power yet the fan doesn't spin on any of the speeds, even when the fan blade is given a little push (either way). The fan blades are very free to move and the fan looks pretty new (so I'm not ruling out a d.o.a.).

I think it's wired up like this:

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(except it's not a 'start' cap / winding but 'run' on these motors isn't it)?

Measuring ohms from neutral (basically across the L/N on the mains plug) I get:

219 Ohms on speed 3, 375 on speed 2, 393 on speed 1 (slowest) and infinity with it off (of course). ;-)

Measuring between the 3 wires coming out of the motor to the switch I get: N-S3 = 219, S3-S2 = 157 and S2-S1 = 46 ohms (so doesn't quite add up correctly (422 v 393)?

There is also a run (?) cap of 2uF that tests out on my DMM (as 2uF) (and open circuit on the ohms test) and a run winding that measures

375 ohm. Measuring the voltage across the cap with it on speed 1 gives 206V (does that sound right)?

I can't see any thermal trips so apart from the cap breaking down under load (I have one on order just in case) or it being wired up incorrectly (within the motor, can't get at much in there without cutting it open) I can't see what the cause of it not running is?

Any thoughts or ideas please?

Cheers, T i m

Reply to
T i m
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Normally these things use a squirrel cage motor plus 2 series caps for speed reduction.

NT

Reply to
tabbypurr

Very sure this is stock and deffo only one cap.

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

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Cheers, T i m

Reply to
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.

Reply to
Roger Hayter

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.

Reply to
Fredxxx

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.

Reply to
Capitol

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.

Reply to
Fredxxx

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

Reply to
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

Reply to
tabbypurr

I think I would call them shaded pole induction motor:

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

Reply to
Fredxxx

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

Reply to
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

Reply to
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

Reply to
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!

Reply to
Fredxxx

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

Reply to
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

Reply to
Brian Gaff

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

Reply to
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

Reply to
T i m

Have you stripped the fan and oiled the sintered bearings?

Reply to
Capitol

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

Cheers, T i m

Reply to
T i m

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