Dimmer vs speed control

[mark32]

I was asked today what the difference is between an incandescent dimmer and a ceiling fan speed control was and all I could come up with was the fan will hum on a regular dimmer. I searched online for some technical info but couldn't find anything. Can anyone give a brief description about the differences between the two types of devices? Thanks

 

[480sparky]

Here's a normal sine wave:

A dimmer works by chopping off portions of that sine wave, in effect turning the power on and off really fast:

 

[LarryFine]

Mark, some dimmers will control some fans, and vice versa, but the design for a motor load is different, but I can't be more specific than that.

One thing I do know is that the dimmer-type of motor speed controller starts with 'hi' when you turn it on, and slows as you advance it, while the dimmer starts at 'lo' and brightens as you advance it.

That's to assure (well, increase the likelihood) that the motor will get up to speed from a stop faster, increasing motor life through less heating.

 

[B4T]

Fan speed controls start you at high speed, so you don't put a strain on the motor to get started. Lighting dimmers start you anywhere you like.. IMHO

 

[ce2two]

ce2two

ce2two

u ever think ,a dimmer ,typical dimmer is rated at 600 watts,resistive ,were not talking about starting a motor and having to over come inertia to get started ever wonder why it might hum.......... ,u don't use a 600 watt dimmer to contol flourescent lighting either ,kind of like doing away with across the starters and going with ADJ. freq. drives, soft start controllers ?