| 摘要 |
PURPOSE:To prevent spread of abnormal state by feeding an abnormality signal when the difference between an actual rotary speed of an AC motor and a commanded rotary speed enters a preset abnormality judging zone and switching the AC motor to a backup motor. CONSTITUTION:A variable-voltage variable-frequency power source 3 feeds a voltage, at a frequency corresponding to a speed set signal fed from a commander 7, to an induction motor 8 through an output transformer 4 and an output switchgear 5, thus rotating the motor 8 with a command speed. The motor speed is detected through a rotation detector 10 and fed through a P/I converter 11 to an abnormality judging unit 12. The abnormality judging unit 12 compares the actual speed of the induction motor 8 with the speed command, and when a judgement is made that the difference is within the abnormality region to be defined by an abnormality judging region setter 13, an abnormality detection signal is produced. Then the output switchgear 5 and a backup power source switchgear 16 are opened and closed, respectively, to operate an alarm 14 thus informing occurrence of abnormality to an operator. |
