PLC is a kind of electronic system designed for applications in the industrial design environment for digital operation, in the implementation of the logic operation PLC timer, sequence control PLC timer, timing, counting and arithmetic operations in its internal storage operation instructions elevator, and through digital or template of the input and output of machinery or production process control of various types.

PLC has been widely used in elevator industry because of its reliable operation elevator OMRON , simple programming elevator OMRON , convenient operation and short design and debugging cycle. According to incomplete statistics OMRON , Tianjin used 4100 elevators, elevators with PLC control, there are 562 units, of which AC double speed elevator using Japan OMRON company produced C series, PLC majority. According to the elevator part of site safety inspection of the AC contactor, the stator winding method on impedance switch contactor of acceleration and deceleration control, terminal safety protection by mechanical force speed switch, limit switch and limit switch. Although this design can satisfy the operation needs, but in use may appear adhesion, contactor, contact spring failure can not be reset, misoperation, switch electrical components such as mechanical damage failure will occur at the top or bottom squat "accident. To prevent the occurrence of such failure, in addition to improving the quality of construction quality and components, we can use not to make full use of PLC timer and a relay, with the fault diagnosis function of PLC, realize the end station protection program, solve these problems, so as to improve the safety and reliability of the elevator.

The following describes the application of PLC timers in end station protection.

When the elevator is directed upward, upward direction relay SFJ0015, express KF, train auxiliary contactor contactor KY0501, lock relay MSJ, contactor SX0502 are upward pull power, brake open, lift up. When the car hit forced speed switch SQH0016, PLC internal latch relay KRRP1001 pull power, the timer Tim10, Tim11 start timing, the timing of the length of time the visual layer from the end station and a ladder speed setting. Forced speed switch, by express elevator operation to train operation, under normal circumstances, the upstream layer lift should stop. If the car did not stop and continue upward, when the Tim10 value is reduced to zero, the normally closed contactor disconnect, slow MY0503 and ascending contactor SX0502 loss of electricity, the elevator stops running. In the car to meet the arrogant force speed modification after the switch SQH0016, for some reason the elevator failed to transfer for the traffic operation, and train contactor KY0501 failed to release, when the Tim11 value is reduced to zero, the normally closed off, running express contactor KY0501 and upstream contactor SX0502J are the loss of electricity, the elevator stops running. Therefore, whether it is idle or run express operation, as long as the forced switch SQH signal speed, regardless of whether the other end station protection switch action, with the help of Tim10 and Tim11 were able to make the elevator to stop running, so that the elevator terminal more reliable protection.

When the elevator down, as long as the selected instruction, downlink relay XFJ0014 electricity the normally open closed latch relay keep is reset, Tim10 and Tim11 were the loss of electricity, the normally closed closed ready for lift down to normal. The protection principle of the lower station is similar to the protection of the upper station, and is no longer repeated.

This method has no influence on the normal operation of the elevator and has been in good running condition. Since the instructions of different types of PLC systems are not exactly the same, the functions are different, depending on the specific circumstances, but the general meanings are basically the same.