author: Potensi- Ella
In the actual field maintenance encountered many elevator failures caused by encoders.  There are many kinds of encoder faults, which can be divided into two categories: first, encoder use problems (packaging manufacturing, transportation collision, non-standard operation in the installation process and non-standard follow-up maintenance); second, external interference to signal transmission.
The commonly used encoder is the Haidhan encoder, the following introduces several encoder failure cases:

Case analysis  

Case 1: an elevator, the flat layer is not accurate and there is a vibration phenomenon of "teng teng" in the running stroke.  The fault could not be eliminated on site. Later, after our inspection, we found that the connection line of the encoder was damaged, and the fault was eliminated after replacing the connection line. 

Case 2: An elevator appeared abnormal phenomenon after conducting the linkage test of empty car safety pliers and speed limiter. The elevator crawled about 50mm after starting the floor selection, and then stopped.  Through the investigation, the signal connection between the encoder and the frequency converter is unstable.  

Case 3: A variable frequency asynchronous elevator often stopped suddenly in operation.  The elevator can run normally again after automatic leveling.  It was checked that the fault was not caused by a faulty brake circuit.  It is not caused by the safety circuit and the door lock circuit.  But because the serious wear of the encoder leads to the sudden interruption of the signal in the operation of the elevator.  

Case 4:1 elevator car vibrated strongly during normal fast operation.  Elevators shake up and down regularly, especially when they run on multiple floors.  Examination of the elevator's main circuit and drive unit has not found the true cause.  After asking the owner, that is someone in the machine room to clear debris, the elevator began to appear above phenomenon.  After that, the outer parts of the tractor and control cabinet were inspected emphatically, and it was found that the distortion of PG grounding copper skin installed at the tail for speed feedback made the motor shaft and the shaft sleeve of the encoder out of sync during the operation of the elevator.  Then add one connecting copper sheet again. After the replacement, the fault is rectified  

break encoder  
The encoder code disk is damaged                             Encoder spindle wear


Encoder wire damage                                            The encoder is damaged due to collision on site   

Through the above cases, we found that no matter the encoder signal line is false connection, code disc wear, encoder shaft sleeve and motor shaft are not synchronized, etc., will cause the loss of encoder signal acquisition, and such faults will cause the abnormal operation of the elevator.  

In the case of no signal interference on site, the easiest way to judge the encoder failure is to turn the encoder forward and backward on site and observe whether the frequency converter has signal feedback. If there is signal feedback, the encoder is normal; if there is no feedback, the encoder is faulty