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question about dimmer

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EN0

Member
does ceiling fan dimmers (triac based speed controllers) reduce fan motor's lifetime?
The dimmers in fans are actually potentiometers. Every motor has a maximum currrent it can handle. If you limit the current, providing less and less current, the fan will go slower but the lifetime will go up. If you go over the current level, the lifetime shortens. It's just like an LED. On LED specs, you'll find something like 20,000 hours or 30,000 hours based on a specified current which is usually 20-30mA.
 

aruna1

Member
The dimmers in fans are actually potentiometers. Every motor has a maximum currrent it can handle. If you limit the current, providing less and less current, the fan will go slower but the lifetime will go up. If you go over the current level, the lifetime shortens. It's just like an LED. On LED specs, you'll find something like 20,000 hours or 30,000 hours based on a specified current which is usually 20-30mA.
well what i meant is triac or SCR based phase control dimmers
 
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bountyhunter

Well-Known Member
maybe they changed AC motors recently, but a rheostate (pot) "dimmer" to an AC induction motor won't work. Take the control guts down out of a three speed fan and you will find a selector switch and two capacitors:

speed 1 = cap 1

speed 2 = cap 2

speed 3 = cap 1+2

There is no pot. I did buy a fan a long time ago with a "solid state" speed controller with a pot and the motor failed along with the controller. If you starve the current going to an AC fan, the motor will eventually stall at a very abrupt point. That's how I have seen fan motors work. Running the motor slower (near stall) actually makes it get hotter.
 
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vsmGuy

New Member
TRIAC based dimmers do not regulate current. They change the "duty cycle".

Yes aruna1, poorly designed, minimal parts dimmers DO reduce the life significantly - mainly via overheating of the fan coils as well as no "soft start".
 
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