Tips for confirming elevator failures - Solutions - Huaqiang

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1. Example of Diagnosing a Faulty Rotary Encoder Example 1: A GPS-‖ elevator was experiencing inaccurate leveling, with a "Teng Yi Teng" (jittery) sensation during operation. After extensive troubleshooting, it was found that the encoder had 9 photoelectric sensing holes blocked by dust. Cleaning the encoder resolved the issue. Example 2: An P90-50 elevator would crawl about 50mm after starting and then stop. Since no other abnormalities were evident, the problem was suspected to be with the rotary encoder. Further inspection revealed a loose connection between the encoder and the microcomputer. Example 3: A VVVF elevator would suddenly stop during operation, then restart after leveling. After ruling out brake circuit issues and safety circuit problems, the cause was identified as sudden wear on the encoder, leading to signal interruption. Example 4: A GPS-CR elevator experienced strong oscillations during high-speed operation, especially in multi-floor scenarios. After checking the main board and drive unit without success, it was discovered that debris had been removed from the machine room, causing grounding issues. Replacing the connecting copper piece fixed the problem. Faults caused by faulty encoders are common and often difficult to diagnose. Sometimes even after checking, the issue remains unclear. A simple method is to disconnect the encoder’s feedback and run the motor in open-loop mode. If the motor runs normally, the problem likely lies with the encoder. Otherwise, the issue may be elsewhere. However, always ensure the elevator is not operated at the top or bottom floors when the feedback is disconnected for safety. 2. Quick Diagnosis of Door Lock Faults Door lock faults make up a significant portion of elevator issues. In most cases, you can check the control panel or fault codes to identify the problem. For low-rise buildings, it's easy to check each floor one by one. But for high-rise buildings with 40 or more floors, a more efficient approach is needed. When the elevator won't operate due to a door lock fault, first locate the car door and hall door switches on the terminal block. Check if both are closed and functioning properly. If the car door switch is on but the hall door switch is off, use a segmentation method to narrow down the issue. Start by shorting lines 01 and 11 on the door lock circuit so the elevator can move. Then, go to the car top and check lines 01 and 10. For a 40-floor building, go to the middle floor, say the 20th, and open the doors at the 10th floor while keeping others closed. Use a multimeter to test the connections. If the meter shows continuity, the issue is likely in the upper half; otherwise, it's in the lower half. Repeat this process to quickly locate the faulty floor. 3. Diagnosing Door Knife Touching the Roller Fault Sudden elevator stops can be caused by various factors, such as a momentary door lock circuit failure, a tension device touching the rope, or the door knife contacting the roller. To determine if the door knife is touching the roller, especially in PLC-controlled elevators, insert a program snippet between OUT (M21) and OUT (M111), where M21 is the running relay and X14 is the door lock contact. After a fault occurs, check the counter C224 in the PLC. If the K value increases by one, it confirms that the door knife has touched the roller. As a technician, you'll face many unusual situations. By carefully analyzing each case and summarizing your findings, you can develop effective shortcuts that will help you solve similar issues faster in the future.