Electric fans

[Bluenoser]

Does a multi-speed fan use less current (cheaper)when it is run on the slower speeds or is it the same usage regardless of speed? Cheers.

[stanleyman]

It is cheaper to use the slower speeds, but not by much if it is a domestic fan.

[xrayspecs]

Isn't the power input the same, and gearing within the fan that determines the speed?

[stanleyman]

I've never seen a gearbox on a fan, it's cheaper to do it electricaly.

[Pete1956]

Yes it will be cheaper. The mechanical input power for a fan blade is proportional to the cube of fan speed, but the motor power will not change in the same relationship because it will still draw some current when completely off load.

If for arguments sake you had a geared system with a constant speed motor (unusual, not seen one myself) and changed gear to a lower speed, the torque required from the motor would drop and therefore so would the motor input power, same as above.

[rancid]

I agree with stanleyman.....cheaper to produce.....and run without gears.

[fluffybet]

will it be long till we see invertor / thyrister control on fans?

[xrayspecs]

I'm a big fan of over engineering!