Expert elevator repairmen are those who can analyze the causes of malfunctions based on their symptoms and quickly determine the true cause or the specific location of the malfunction . Therefore, repairing elevators requires not only constantly summarizing and accumulating experience in troubleshooting, but also mastering techniques for confirming malfunctions.
Confirmation of elevator rotary encoder malfunction
Example 1: An elevator was not leveling accurately and exhibited a "jumping" phenomenon during its travel . After much effort and many detours during repair, it was finally discovered that the problem was caused by dust clogging several photoelectric sensor holes in the rotary encoder. Cleaning resolved the issue .
Example 2: An elevator exhibited an abnormal phenomenon after undergoing an empty car safety gear-speed governor linkage test. After selecting a floor and starting, the elevator crawled for about 50mm before stopping . After much thought , since the elevator had the necessary operating conditions and there were no other obvious abnormalities, the problem must have been with the rotary encoder . The cause was indeed found to be a loose connection between the rotary encoder and the microcomputer .
Example 3: A VVVF elevator frequently stops suddenly during operation , then automatically levels and resumes normal operation . Inspection revealed that the fault was not caused by a faulty braking circuit, nor by momentary interruptions in the safety circuit or door lock circuit. Instead, it was caused by severe wear of the rotary encoder, resulting in sudden signal interruptions during elevator operation .
Example 4: An elevator was operating normally during maintenance, but the car vibrated strongly during high-speed operation, and the elevator shook rhythmically up and down, especially noticeable when running on multiple floors . After inspecting the elevator's main circuit printed circuit board and drive unit, the root cause could not be found . Upon questioning the owner, it was learned that the elevator began exhibiting these symptoms after someone cleared debris from the machine room . Further inspection of the traction machine and the control cabinet revealed that the PG grounding copper sheet at the motor's tail end, used for speed feedback, was twisted and deformed, causing misalignment between the motor shaft and the Pc bushing during operation . After re-machined and replacing the connecting copper sheet, the fault was eliminated .
Elevator malfunctions caused by rotary encoders are not uncommon, and troubleshooting them is quite time-consuming. Sometimes, even after troubleshooting, concerns remain . Therefore, this article introduces a simple method to confirm rotary encoder faults. It is the rotary encoder that creates a closed-loop speed control system between the microcomputer, frequency converter, and motor. Therefore, if the rotary encoder malfunctions and the feedback signal is abnormal, it will inevitably affect the normal operation of the motor . If we simply disconnect the rotary encoder feedback—turning to open-loop control—and the motor still runs normally at high speed, then we can confirm that the elevator fault is indeed in the rotary encoder. Otherwise, the fault should be sought elsewhere . This is the theory behind confirming rotary encoder faults.
