Why does the power consumed is always constant even if a fan
speed is altered?

Answer Posted / 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

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