My fairly old ceiling fan needs a speed control switch replacement. It's a three-speed fan with a three wire switch. There are no capacitors; instead it appears to use some kind of smallish transformer looking device for speed control. My Googling to find what the circuit might look like has been fruitless. Can someone point me toward an educational source of speed control schemes for these fans or else explain to me how mine works?
I'd guess a tapped inductor.
You can buy a replacement at most larger hardware stores fairly cheap, probably for less that you could repair the bad one.. Usually, it is the switch contacts that fail. If the inductor fails, you'll smell burning shellac of Formvar insulation.
-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
if its runs at high speed only control is burned out or open, if it runs high speed on all settings control is short out or burned out. you can replace them with a capacitor 3 speed control, ive done this to some fans. goto a electrical store to get them, some have the circuits with them to follow.
ainstead
speed
Well, the change to a capacitor control has some appeal. I suspect that if I could find the right switch for this thing it would be as good as new. The replacement switches at the hardware store say they are for 3 or 4 wire applications; however, there is no drawing to show how to hook up the three wire system. All the combinations I've tried so far have yielded less than desirable results. It might be about time to trace all the wiring and try to figure out what makes it tick.
Thanks to all who have responded.
Update:
The fan is working just swell now. Figured out that it does indeed use some kind of inductance control. The transformer looking thing had only three wires. The middle lead went to the motor main and start windings. First speed was one of the inductor legs in series with the motor. The next speed was the other leg, and the final speed was produced with both legs in parallel. The legs were not equal in resistance, thus I assumed they had different inductance.
Could not find a speed control witch like the original three-wire one. Bought one of those two-layer 5 to 8 wire speed control switches and wired up all the contacts on the first layer and one of the contacts on the outer layer to get the equivalent contact sequence as the original switch.
Are variable inductance speed controls like the one for my fan very common? What is their advantage?
What else would you use?
During my research into the problem the most common technique mentioned involved switching different valued capacitors in and out of the circuit. Not once did I encounter a variable inductance circuit.
It's a cost/size trade-off. Until recently capacitors would have been too large or expensive or both. It seems this has changed.
Most table/floor fans and many other appliances have the inductors 'built in' as part of the motor.
capacitor droppers are a bit more energy efficient, due to the R in wound inductors.
NT
To reduce the noise of an extractor fan in the toilet, I've successfully slowed down by adding a series capacitor (rated at much more than mains voltage. I'm not sure what kind of fan it is, but it's probably an induction motor. However, the value of the capacitor is very critical. Too little, and it really slows down. Too much, and it runs up to full speed (as if the capacitor wasn't there). Any change of mains voltage is very apparent. The value of the capacitor has to be determined by trial and error. Ian.
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