To immediately stop rotation of a motor so as to insure safety of an operator, when frequency of alternating current power output from an inverter device is detected and the frequency becomes higher than a reference value, namely when an elevator begins to run away by a trouble of the inverter device and the like.
When low speed elevating operation of an escalator is carried out, by pushing an elevating operation switch O.UP, the charge coil UPC of an elevation contact UP is excited, usually opened preliminary contacts UPa1-UPa4 are closed, and an inverter device 21 receiving an operation direction command of elevating direction reconverts three-phase current power from a three-phase current power source 4 and outputs. The output current is detected by a current detector 221, converted to an inverter current periodic signal CINV of H by positive half period by a current periodic signal generating circuit 2221, the period Ta is compared with the period Tb of a reference periodic signal CSTD output from a reference period generating circuit 2222 by a speed increase judging circuit 2223, and at Ta≤Tb, an abnormality stop signal EST for stopping the output of the inverter device 21 is output.
ANDO TAKEYOSHI
CHIBA TADAAKI
NISHIKAWA SHIZUO
WAKABAYASHI NOBORU
