Patent ID: 7303241

Claim:
A pump drive motor control apparatus for controlling a motor for driving a pump, comprising: control means for controlling rotational speed of the motor through on-off control performed such that supply of electricity to the motor is resumed on the basis of a result of comparison between a predetermined threshold and a voltage which the motor generates in a state in which supply of electricity to the motor is stopped and such that the supply of electricity is stopped after the supply of electricity is continued for a predetermined period of time; decreasing-speed-index obtaining means for obtaining a voltage-decreasing-speed index value indicative of a rate of decrease of the voltage which the motor generates in the state in which the electricity supply is stopped; and average-rotational-speed changing means for changing a parameter which affects an average rotational speed of the motor in accordance with a rate of decrease of the voltage represented by the obtained voltage-decreasing-speed index value, wherein the decreasing-speed-index obtaining means obtains, as the voltage-decreasing-speed index value, a time which, after having reached a first voltage greater than the predetermined threshold, the voltage requires to reach a second voltage which is greater than the predetermined threshold but lower than the first voltage.