I have a ceiling fan fitted in my bedroom - an Encon 78376 from TLC. It came with a four speed controller, but only the slowest speed is usable. On the fastest speed it sounds like a helicopter taking off and I don't even want to be in the same room.
On the slowest speed the motor is virtually inaudible, but there is a bit of noise from the fan blades, and I would like to slow all the speeds down a bit. Last year I tried a different fan controller which reduced the speed but it made the motor very noisy.
Is it possible to put a resistance in the circuit to slow it down? If so what do I need?
I had a look in the CPC catalogue and am very confused.
Tough one to call. Chances are the existing speed controller is an electronic PWM device. If you stick another PWM controller in front of that, you will at best get erratic running with lots of noise, or more likely, get nothing at all or a damaged speed controller.
You could try dropping the voltage supply to the controller, this would hopefully maintain smooth quiet running. However drop it too much and the PWM circuit will begin to misbehave. The simplest way to do this would be a step down transformer.
Finally you could attempt to attenuate the output of the exiting PWM controller. This saves any problems with interfering with its operation due to reduced input voltage, but adds complexities of its own. A transformer on the output would probably not be a good idea because many PWMs will not like an inductive load of that type (all the "edges" and HF content of the PWM waveform can generate some nasty back EMF from the transformer). You may be able to implement some form of shunt or voltage divider, however you will need to use components that are capable of dissipating the same sort of power as you would expect the motor itself to handle.
I think I would try the second option myself. If you have access to a variac you could work out the sort of voltage you want to drop to, and hence the turns ratio required on the transformer.
How does the existing controller work? does it select windings on the motor or is it an electronic (Triac PWM) device? If it's electronic you will probably find that the switch selects resistors to control the charging time of a capacitor, try increasing the value of the "slow running" resistor. By looking at the existing values you should be able to select a suitable replacement - or, if there's space, you could replace it with a pot.
If the controller was made specifically for that model of fan, it is most likely just switched capacitors. There is no reason to use higher cost control electronics, those would only need to be present if it was designed to control a range of different fans.
If so, all you need do is replace the caps with smaller ones to get whatever speed you want - down to a point. The motor will only start reliably at so low a speed, go any lower and you risk frying the motor by it stalling. The good news is that since load on a fan is proportional to motor speed cubed, you can go quite a long way down. But... it sounds like you already have. Its always possible that regardless of what you do controlwise, the motor might not start reliably any slower.
If so, a more complex controller would be needed, one that applies full power momentarily, and senses a stalled motor.
BTW if its switched caps, keep the order of speeds the same, as these controllers typically switch on at full then go down thru the power levels as a means to ensure reliable starting. Failing to do this can mean a small risk that after 20 years one day it doesnt start up, and gets fried.
If your fan has a thermal cutout, as the better ones do, you can not worry about the stall issue, since if it does it will just trip the thermal cutout. There are many fans on controllers with no startup surge and no thermal cutout, so it can be done, and is, its just a slight risk to the motor.
ha. To the op, if speed control is going to be a hassle, is it buzzing, rattling, cyclic shaking, creaking, sub-20Hz or wind noise? Each has its own cure.
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