Method for controlling rescue operation of elevator car during power failure

A method for controlling a rescue operation of an elevator car during a power failure by using an elevator system including:

• a rope;
• an elevator car connected to one end portion of the rope, and transferring passengers or cargo;
• a balance weight connected to the other end portion of the rope, and keeping the balance with the elevator car;
• a traction pulley for moving the car in a vertical direction by winding or releasing the rope;
• a three-phase alternating current synchronous motor for providing a driving force rotating the traction pulley in a clockwise or counterclockwise direction during the normal operation, and provided with a permanent magnet generating electric power by rotating due to a weight difference between the balance weight and the car during the power failure;
• a three-phase alternating current power source for supplying an alternating current power;
• a converter for converting an alternating current from the three-phase alternating current power source into a direct current;
• an inverter having switching devices, each device provided with a gate for being controlled, for inverting a direct current from the converter into a three-phase alternating current, and outputting it to the motor;
• a condenser for charging, smoothing and outputting a direct current from the converter during the normal operation, and receiving an electricity generated from the motor through the inverter, and charging, smoothing and outputting it during the power failure;
• a power failure detector connected to the three-phase alternating current power source for detecting the power failure;
• a controller for receiving a power failure detection output from the power failure detector and for outputting a speed command signal and an excitation component current command signal to the motor;
• an encoder outputting a pulse signal corresponding to a rotation angle of the motor;
• a current detector for detecting and outputting each phase current of the three-phase alternating current outputted from the inverter to the motor;
• an inverter controller outputting voltage command signals of pulse width-modulated three phases on the basis of the speed command signal and the excitation component current command signal from the controller, each phase current from the current detector, and the pulse signal from the encoder;
• a gate driving unit for controller driving a gate of the inverter;
• and
• a direct current voltage detector for detecting a direct current voltage at both ends of the condenser and supplying it to the inverter controller,
• wherein, the inverter controller including;
• a speed detector for detecting a current speed of the car according to the pulse signal from the encoder, and outputting a detection speed signal;
• a speed controller for outputting a torque component current command signal compensating for a difference between a command speed according to the speed command signal from the controller and a detection speed according to the detection speed signal from the speed detector;
• a first coordinate converter for converting and outputting the current signals for each phase from the current detector into an excitation component current detection signal and a torque component current detection signal according to the pulse signal from the encoder;
• an excitation component current controller for outputting an excitation component voltage control signal compensating for a difference between an excitation component current command value according to the excitation component command signal from the controller and an excitation component current detection value according to the excitation component current detection signal from the first coordinate converter;
• a torque component current controller for outputting a torque voltage control signal to compensate a difference between a torque component current detection value according to the torque component current detection signal from the first coordinate converter and a torque component current command value according to the torque component current command signal from the speed controller;
• a second coordinate converter for converting and outputting the excitation component voltage control signal from the excitation component current controller and the torque voltage control signal from the torque component current controller into voltage control signals of three phases according to the pulse signal from the encoder;
• and
• a pulse width modulator for pulse width modulating and outputting the voltage control signals of three phases outputted from the second coordinate converter,
• the method comprising;
• a step for obtaining the electricity generated by rotating the synchronous motor due to the weight difference between the balance weight and the car during the power failure;
• a step for charging the electricity in the condenser;
• and
• a step for gradually increasing a rotation speed of the synchronous motor from a starting time thereof to a predetermined time for speed controlling matched with a charging voltage of the condenser at an initial stage of the power failure.