Elevator rescue apparatus during stoppage of power supply

Claim 1

An elevator having a rescue apparatus during a stoppage of power supply, the apparatus operating the elevator with an emergency power source while the A.C. power source is abnormal; comprising: (a) a converter which converts alternating current of the A.C. power source into direct current, (b) an inverter which is connected to said converter and which inverts the direct current into alternating current, said inverter being constructed of a bridge circuit in which a plurality of arms are connected in parallel, said each arm being composed of a pair of transistors connected in series and a pair of diodes inserted between said pair of transistors and connected in series in the same polarity as that of the series transistor circuit, nodes of the pairs of diodes being respectively connected to a motor for driving a cage of the elevator, to feed the motor with the alternating current of variable voltage and variable frequency, (c) the emergency D.C. power source which is connected across D.C. side input parts of said inverter, (d) first switching means inserted between said emergency D.C. power source and said inverter, said means being held in an open state while said A.C. power source is normal and being brought into a closed state to electrically connect said emergency D.C. power source to said inverter when said A.C. power source has become abnormal, and (e) second switching means connected in parallel with said pair of diodes of said each arm, said means being held in an open state to keep said pair of diodes effective while said A.C. power source is normal and being brought into a closed state to form a circuit bypassing said pair of diodes and to keep a voltage polarity of a D.C. side of said inverter unchanged when said A.C. power source has become abnormal.