摘要 |
PURPOSE:To detect the disconnection of a speed detector rapidly by conducting the operation of counting each time in response to the presence of a speed- detecting signal and outputting a disconnection-detecting signal when the counting value of a counter reaches a predetermined value. CONSTITUTION:A speed detecting circuit 6 outputs a speed signal S5 obtained by F/V converting a digital speed-detecting signal S4 corresponding to the rotational speed of an induction motor 3. A speed-command value arithmetic circuit 9 transmits a deviation signal between a speed-setting signal S8 and the speed signal S5 over an inverter 10. A disconnection detecting circuit 11 starts its operation after the speed-setting signal S8 is inputted and a fixed time passes, and conducts the operation of counting at every input of a speed detecting signal S4. A disconnection-detecting signal S11 is transmitted over the inverter 10 when a counting value reaches a prescribed value. |