http://maxelectrical.tradeindia.com/fan-regulator-1133953.html a fan regulator is a device put in series with fan to alter its speed.it can provide different value of resistance through a rotatory switch numbered 1 ,2,3,4,5.At position 5 the speed of fan is max.at 1 its min.as resistance of regulator is max.at that position.[PLAIN]http://maxelectrical.tradeindia.com/fan-regulator-1133953.html[/QUOTE]
This is unlikely to insert varying resistances in series with the fan. This probably electronically switches just a portion of each AC cycle through the fan, thus reducing the average voltage and hence reducing the fan's speed. The part of the voltage that isn't used by the fan represents saved power, rather than wasted power (generating heat) that you would see with added resistance.