DRIVER OF AIR BLOWER, ETC., ROTATING SPEED DETECTOR OF AIR BLOWER, ETC., MOTOR, AND AIR BLOWER

摘要

PURPOSE:To make stable control of a rotating speed of a motor by comparing the detected rotating speed of the induction motor with a set desired rotating speed and by determining a conduction ratio of a bidirectional conduction element so that there may be no difference between the detected rotating speed and the set one. CONSTITUTION:A rotating speed sensor 5 detects the rotating speed of an induction motor 1. A signal generator 6 generates a pulse signal which has a frequency corresponding to the rotating speed detected by the rotating speed sensor 5. An arithmetic means 7 calculates the optimum conduction ratio of a TRIAC (a bidirectional conduction element) 2 based on the pulse signal from the signal generator 6. A gate drive circuit 8 gives a gate signal to the TRIAC 2. In other words, the rotating speed of the induction motor 1 detected by the rotating speed sensor 5 and the set desired rotating speed are compared with each other and the conduction ratio of the TRIAC 2 can be so determined that there may be no difference between the two rotating speeds. By this method, a stable control of a rotating speed of the induction motor 1 is available.