Thyssen Elevator Electrical Fault Diagnosis Techniques
Safety circuit
Function: To ensure the safe operation of the elevator, many safety components are installed on the elevator. Only when each safety component is in normal condition can the elevator operate, otherwise the elevator will immediately stop running.
The so-called safety circuit refers to the installation of a safety switch in each safety component of the elevator, which connects all safety switches in series to control a safety relay. Only when all safety switches are turned on and the safety relay is activated can the elevator be powered on for operation.
Common safety circuit switches include:
Machine room: control panel emergency stop switch, phase sequence relay, thermal relay, speed limiter switch
Hoistway: Upper limit switch and lower limit switch (some elevators place these two switches in the safety circuit, while others use these two switches to directly control the power supply)
Pit: rope break protection switch, pit maintenance box emergency stop switch, buffer switch
Inside the car: Emergency stop switch of the control box
Car roof: safety window switch, safety gear switch, car roof maintenance box emergency stop switch
Fault status:
When the elevator is in a stopped state, all signals cannot be registered, and both fast and slow trains cannot run, it is suspected that the safety circuit is faulty. You should go to the control screen in the computer room to observe the status of the safety relay. If the safety relay is in the released state, it should be judged as a safety circuit fault.
Possible causes of malfunction:
1. The phase sequence error or missing phase of the input power supply causes the phase sequence relay to operate.
2. The elevator is operating under overload or locked for a long time, causing the thermal relay to act.
3. It is possible that the overspeed of the speed limiter may cause the speed limiter switch to act.
4. The limit switch action is caused by the elevator hitting the top or sinking to the bottom.
5. The pit rope break switch operates. It may be due to the governor rope jumping out or being too long.
6. Safety gear action. The cause should be identified. It may be due to the overspeed action of the speed governor, incorrect operation of the speed governor due to loss of oil, loss of oil on the pit rope pulley, foreign objects (such as mice) getting entangled in the pit rope pulley, and too small clearance between safety blocks.
7. The safety window is lifted by someone, causing the safety window switch to operate.
8. Some emergency stop switches may have been pressed by someone.
9. If all switches are normal, check if their contact points are in good condition and if the wiring is loose.
In addition, although the safety circuit of many elevators is normal and the safety relay is also engaged, a pair of normally open contacts are usually taken from the safety relay and sent to a microcomputer (or PC) for testing. If the safety relay itself has poor contact, it can also cause a malfunction in the safety circuit.
