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Re: Light Dimmer to Adjust Spark Gap Fan?
Tesla List wrote:
> Original Poster: "Steve Young" <youngs-at-konnections-dot-com>
>
> Adam,
>
> In general, lamp dimmers will only work properly with "universal" or AC/DC
> type motors. Typically, these have brushes and are used in electric
> drills, vacuum cleaners, electric lawn edgers, etc. Your fan motor likely
> is an induction motor which is best controlled by a small variac, tapped
> transformer, rheostat, series light bulbs, etc. which do not mess up the
> sinusoidal waveform.
Actually SCR controllers designed for inductive loads work quite well for fan
controls. The only minor problem is that since most fans are square-law
devices, most of the speed control will be at the end of the dial but that
would be true with any control. The "dimmers" designed for ceiling fan speed
control work quite well. Some Lutron commercial light dimmers work well, some
don't. I've had great success in the past with the Lutron units but the last
one I bought a couple of days ago controls very poorly working into an
inductive load. I have not looked inside to see if the circuit is different
or if this one is just a fluke. I hope it's a fluke because the Lutrons can
be had at Home Depot in capacities up to 2 kw at a very reasonable price.
Another type device is the dimmer labeled suitable for fluorescent lamp
dimming service. Lastly, there are available fairly inexpensive neon sign
dimmer modules that work fine with motors. I get mine from West Coast Custom
Design (602 820 9517) A small in-line unit is about $12 and a higher capacity
unit that looks like a wall-wart with a knob on the side is about $20.
Those little shaded pole motors in small fans don't seem to care too much
about wave form. They growl a bit at low speed on phase angle control but
they don't overheat. Ditto when run on square wave inverters.
john
--
John De Armond
johngd-at-bellsouth-dot-net
Neon John's Custom Neon
"Bendin' Glass 'n Passin' Gas"