Took a look inside a controller today, they have 1.8UF and 3.6UF (at
50hz) capacitors (motor was labelled 65w)
Another thing you could to, if you have access to someone who is reasonably accurate in metal folding, is to fold the fan blades down a little bit more to change the pitch. (alternately you might try packing washers between the blade and the motor under the mounting screws to tilt it slightly more - dont know if it would work but worth a try)
A friend found that out the hard way years back when unknowingly put 4 blades meant for a 3 blade fan onto a 4 blade fan body and nearly drove himself mad trying to work out why he couldnt get it to go fast enough. He had picked up several fans and a box of blades free from a place that was being renovated and just picked out 4 blades that looked the same.
It was a very small difference in blade angle, but knocked off an enormous amount of speed
definitely would, but whether or not it damages the motor is another matter. as long as there is enough airflow around it to not let it overheat it should be ok ?.
First off, remove the light dimmer from the circuit. Dimmers are known to cause hum/buzzing in ceiling fan induction motors. Ceiling fan induction motors like sine waves. If the fan still buzzes on pure sine wave AC current, the motor has loose/separated stator laminations or loose winding coils on the stator; this is usually not repairable, although a good lacquer bath could theoretically tighten it up.
The older spinner fans (especially ones that do not have a pull chain switch to proivde the lower speeds) used a multiple tapped transformer to provide the lower voltages. It was often too large to fit within a standard wall switch box and was designed for surface mounting on the wall.
There are controls made specifically for ceiling fans that are incremental (not continuously variable) that provide reduced voltages for the lower speeds but keep the sine wave intact. Transformers are no longer used.
Using a capacitor inline with the power to provide the lower speeds is the preferred method in fan manufacturing today. Today's fans and fan controls use a dual stage capacitor - paired together in parallel for Medium and one stage for Low Speed. For 120VAC 60Hz, the capacitor's rated voltage should be at least 240VAC for the speed control capacitors. Speed capacitor values range from 1.5µF to 12µF, with the most common falling between 3µ and 5µ. There should be a running capacitor wired to one end of one motor winding, probably mounted above the motor. The µF value of this capacitor is a good starting point for low speed from speed control capacitors.
Many "universal" ceiling fan controls use 5µF + 5µF or 5µF + 6µF dual capacitors. This is around 2.5µF for Medium and 5µF or 6µF for Low Speed. Slowing the motor beyond the natural Low Speed range, to a "crawl" as it were, with a large capacitor value will likely produce some harmonic noise anyway, but should not buzz.
The numbering sequence for fan controls always starts at 1 for High Speed because fans should always be started on High Speed then lowered to the desired speed. (At a dead stop, the motor is an effective, coupled inductor, add the speed capacitors and running capacitor, and it can create voltages in the circuit higher than component ratings.)
Thank you very much for the explanation Scott. That explains a great many things. My speed controls on these fans are the large tapped transformers exactly as you described. But now what about the current flowing through the capacitor? Is this a concern when selecting a capacitor for the application? Lenny
Thank you very much for the explanation Scott. That explains a great many things. My speed controls on these fans are the large tapped transformers exactly as you described. But now what about the current flowing through the capacitor? Is this a concern when selecting a capacitor for the application? Lenny
Klem,
Typically ceiling fan motors pull less than 1 amp current at 120V and the capacitors used in ceiling fans are large, metallized poly film type AC capacitors. We've never had to consider the current with these capacitors.
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