Answer / vishwanath r

we are controling fan speed by regulator so if we controle
the fan speed there is a voltage drop on regulator
resistance so there is a no changes in power consumption.

Answer / rk

Here our purpose is to control fan speed. By varying the
voltage applied across the fan motor ,we are changing the
speed i.e. Voltage-speed control.The Balance voltage should
apply across the resistnce of the regulator,in that the
power is wasted in the form of heat energy. So overall
Power consumption is same whatever be the speed of the fan.
Power=(Voltage across Motor + Voltage across regulator)* I

Answer / sangeetha

No, at low speeds total power consumed by the fan
(including the power consumed by the regulator) is lower
than that at high speeds.
Refer :http://www.indianfan.org/faq.html

Answer / rakesh

it must be clearly mentioned here that a fan always uses a
single phase capacitor run induction motor , where there
are two windings to provide the two phae supply to generate
the revolving magnetic field , the torque developed is
proportional to the prdct of starting current , main
current and the sine of the angle btwn them , nw whe we
increase the resistance betwn the main wndng and voltage
supply , the voltage remainds the same while the current
decreases , the electrical equivalent of the mech power
developed i.e eicos# decreases , thus power dusnt remain
constant

Answer / elias zard

Nope, wrong.

When you increase the R (resistance to decrease speed of
fan), less current is flowing in the circuit.

Recall basic formula of V = R.I ?

If R increases, I decreases.

Now, the power consumption formula being P = V.I =
R.Isquared, then if I decreases (as proved earlier) and V
stays the same, then P decreases.

There you go :)

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