Method of controlling speed of rotation of motor

摘要

A method for controlling the speed of rotation of a motor by changing the resistance value of a resistor circuit connected in series to the motor and having discontinuous resistance values, including the steps of applying voltage across the motor. Detecting when the applied voltage is lower than a first applied voltage and the resistance value of the resistor circuit is a first resistance value and changing the resistance value of the resistor circuit over to a second resistance value lower than the first resistance value. Detecting when the applied voltage detected is higher than a second applied voltage higher than the first applied voltage and the resistance value of the resistor value is the second resistance value and changing the resistance value of the resistor circuit over to the first resistance value. The first applied voltage and the second voltage are set for permitting the current flowing through the motor by the first applied voltage to be higher than the current flowing through the motor by the second applied voltage.