ROTATING SPEED MEASURING APPARATUS FOR SHAFT OF PERMANENT MAGNET ELECTRIC MOTOR

摘要

PURPOSE: To measure r.p.m. of the shaft of a permanent magnet electric motor without requiring any sensor by providing means for integrating the counter electromotive force generated from a motor during an interval when the motor is connected with a power supply and operating. CONSTITUTION: A capacitor C is connected in parallel with a switch 10 which is controlled to be turned on during same interval as power supply to a motor. The switch 10 is opened only when a voltage V is fed to the electric motor. A predetermined electric signal is delivered from an integration unit 3 and passed, without varying the amplitude, through a disconnector unit 4 to the output terminal 12 of an apparatus 1. The disconnector unit 4 basically comprises an operational amplifier 11 connected in the form of a 'voltage follower'. The apparatus 1 selects values R2 and C appropriately and the electric signal being delivered to the terminal 12 accurately corresponds to the total r.p.m. N of the motor during the time when the voltage V is fed.