The function of the elevator forced deceleration switch and the failure cases caused by it.

Nowadays, elevators have a variety of safety protection devices when running up and down, and their functions and uses are different.
The main functions of the terminal deceleration control switch system are:
(1) When the elevator changes from fast to slow, the car enters this section, and the car hits the deceleration switch, cutting off the high speed and connecting to the low speed operation, so that the upper and lower terminals of the elevator are accurately leveled.
(2) When the elevator runs abnormally, it avoids sinking or hitting the top and ensures the safe use of the elevator.
The height and number of the deceleration switch installation position are generally determined according to the speed of the elevator. Low-speed elevators with a speed of v≤1m/s are generally equipped with an upward forced deceleration limit and a downward forced deceleration limit.

The installation position should be equal to (or slightly less than) the deceleration distance of the elevator. Fast and high-speed elevators with a speed of V≥1.5 m/s are generally equipped with two upward forced deceleration limiters and two downward forced deceleration limiters. Because fast and high-speed elevators are generally divided into single-layer running speed and multi-layer running speed, the deceleration distance is different at different speeds, so they are divided into multi-layer running deceleration limiters and single-layer running deceleration limiters.

Although the principle of the elevator upper and lower terminal deceleration switch system seems to be relatively general, in actual maintenance work, it is often difficult to detect after a fault occurs, and it is difficult to find the fault point, which affects the service quality and the life and work of the owner. The following case is a troubleshooting analysis of the control system of different types of elevator terminals. It is typical and is provided for peer discussion, discussion and reference.

The speed change switch is also called the shaft terminal switch. The upper and lower terminal signals are the forced speed change and floor position correction signals of the elevator. When the elevator speed is ≤1.75m/s, the elevator terminal needs an upper and lower terminal switch and a terminal bridge. The upper and lower terminal switches are installed in the shaft, and the terminal bridge is installed on the top of the car. The upper and lower terminal switches should be installed at the position where the switch is activated when the car sill is 2.5m away from the top (bottom) floor door sill (elevator speed ≤1.75m/s). Ultra-high-speed elevators with elevator speeds ≥2.0m/s should increase the number of terminal stations in order to implement safer protection measures. It is recommended to use non-contact induction switches, such as magnetic induction switches, for terminal switches. Forced speed change generally does not work when the elevator is running normally. Only when the elevator's active speed change does not work, the forced speed change will cause the elevator to slow down.

Incorrect installation positions of the upper and lower terminal stations will affect the leveling accuracy of the elevator at both ends. Taking the upper terminal station as an example, the steps for adjusting the terminal station position are as follows:
1. Install the terminal station switch at a position greater than the speed change distance;
2. The elevator runs quickly to the terminal station, and there will be uneven floors when it stops after the speed change; 3. Immediately set the system to maintenance mode;
4. Measure the distance between the elevator and the leveling floor. This distance is the distance that the upper terminal station needs to be adjusted upward. Similarly, the lower terminal station can be adjusted.

The speed switch also serves as the terminal signal for the elevator. The height of the position will also affect the comfort of the elevator operation.

1. Mitsubishi Elevator strong deceleration switch contact is poor

There is a Mitsubishi HOP elevator in a certain community. The community property reported that the elevator was broken. The maintenance worker rushed to the scene and found that the elevator stopped at a certain floor after inspection. The elevator car door was open and there was no floor display outside the hall. First, check the door machine panel on the top of the car and find that the elevator door is open and closed normally. Then go to the elevator machine room and open the control panel to check whether the light-emitting diodes on the P1 board are working normally. It is found that the 29 and 89 lights are on, indicating that the safety circuit is normal.

The DZ light is also on, indicating that the leveling sensor is working normally. The PP light is also on, indicating that the 380-volt power supply voltage is normal, there is no missing phase, and other points are also normal, such as (41DG, 22, 21, MNT, CWD, DWD, etc.). When adjusting the MON knob to check the fault, the fault code is found to be (D0), indicating that the elevator cannot be restarted and the elevator is "frozen". So the maintenance worker cut off the 380-volt power supply in the machine room. After the power is cut off and reset, the machine room first drives up and down slowly, and everything is normal. After it returned to normal, I flipped the UPC up on the P1 board in the machine room, and the express train moved up one floor. Everything was normal. I flipped the DNC down, and the elevator moved down one floor. Everything was normal. So I let the elevator run normally, and at the same time observed whether the elevator would have this fault in the machine room. The elevator ran for a day and no abnormality was found.

A week later, the maintenance worker received another repair report from the property company, saying that the elevator had no display and the button light was not on. After checking on site, it was found that it was still the same as last time, that the elevator "froze". After cutting off the main power supply, it returned to normal. So we checked all the wiring posts of all the switches in the shaft to see if there was any looseness, and at the same time swapped the P1 board and W1 board with another elevator of the same model and the same floor next to it. After all these were completed, the elevator was restored to operation, and then continued to observe in the machine room. The situation on that day was the same as last time.

But two days later, the same problem appeared again on a different floor. It should be said that all the work of replacement and inspection was done, but the cause of the fault was still not found. The only thing we could do was to check the fault phenomenon and fault code on site. We found that all the indicators on the P1 board were normal, and the W1 board was also normal, just like the previous situation. So we compared the elevator electrical drawings and first measured the voltage of all terminals: 79-00 is DC125V, 420-400 is DC45V, C10-C20 is AC200V, H10-H20 is 105V. After measurement, we found that the voltage of 420-400 was low. According to the reference data, its voltage should be between DC48-54V, but it was only 45V on site. We also checked its power transformer. The output voltage of the transformer was within the technical range. After comparing the drawings, we found that the power it supplied was used by the shaft deceleration switch. After measurement, we determined that the strong deceleration switch at the lower station was not good. Go to the top of the car and drive slowly. Check and find that the deceleration switch contacts occasionally have poor contact, causing the voltage drop. Since the deceleration switch is sometimes good and sometimes bad, and sometimes has poor contact, it will occur once every few days of operation. When the elevator moves out from the first floor and leaves the deceleration switch, the P1 board detects that its voltage is lower than its technical range. The computer board thinks it is faulty and sends a stop signal. When the power is cut off and then supplied, under no load, the voltage it presents appears normal. So based on this analysis, after replacing this strong deceleration switch, the elevator runs normally and no similar faults occur again.

2. The installation position of the deceleration switch of Guangzhou Hitachi Elevator has moved by as much as 10cm

There is a Guangzhou Hitachi (VVVF) elevator. The owner reported that the elevator was locked when it reached the first floor. The community management office immediately sent security to the scene to check and called the elevator company for repair. When the security arrived at the scene, he found that there was no one in the elevator, so he immediately reported the matter to the management office through the Intercom. After receiving the report, the management office thought it was a false report by the residents, and immediately called the elevator company to cancel the report. At the same time, the security guard was arranged to take the elevator up and down. Everything was normal, and the security guard left the scene.
A few days later, the management office received another call from the owner, and it was still said that the elevator was locked. The management office immediately arranged security to the scene and called the elevator maintenance worker. After the security guard arrived at the scene, he found that the elevator was still good. After running up and down, no abnormalities were found. At this time, the elevator maintenance worker had already arrived at the scene. The security guard explained the situation to the maintenance worker. The maintenance worker also took the elevator up and down with the security guard and found no abnormalities. At this time, the security guard reminded the maintenance worker that residents had reported the situation of people being locked up twice in the past few days, so please check carefully. After hearing these situations, the maintenance worker thought that there might be some loose control electrical poles, causing the elevator to stop and shut down, and then automatically reset after the emergency stop. So the maintenance worker started from the machine room, checked and tightened all the wiring poles of the contactor in the machine room control panel, checked and tightened the wiring poles of the safety circuit switches in the well, and checked the hall door locks, but found no suspicious points. After the inspection, the maintenance worker drove the car up and down in the car for more than an hour, and there was no malfunction. After reporting to the management office, he left the scene.

At 8 o'clock the next morning, the elevator company received another repair report from the management office saying: "This elevator has an old problem again." This time, the owner went directly to the management office for maintenance. After receiving the call, the elevator company immediately sent a maintenance worker to the scene, and at the same time conveyed the management office on the phone, asking the resident who reported the repair to wait a moment so as to understand the situation when the elevator malfunctioned. Ten minutes later, the maintenance worker arrived at the management office. The resident immediately said that he took the elevator down from the 8th floor. Before he reached the 1st floor, the elevator suddenly stopped. After a moment, the elevator went up again. After reaching the 2nd floor, it stopped for a while. Without opening the door, it went down to the 1st floor to open the door. He quickly got out of the elevator. After listening to the resident's description, he greeted the resident and went to the scene immediately. According to the fault phenomenon reported by the resident, he first checked the door knife from the second floor, and checked the gap between the door knife and the door ball on the second floor at a slow speed. It was found that the gap between the door knife and the door ball was normal, so he checked the lower strong deceleration switch and found that the screws fixing the lower strong deceleration switch were a little loose. No one paid attention to it at that time. Because every time the owner reported the problem, he said that the fault came from the top to the first floor, so we drove the car from the first floor up to the fourth floor, and then down to the first floor, and ran it up and down repeatedly, while checking the points on the PLC in the machine room to determine the phenomenon when the fault occurred. It did not appear for a whole half day, so we continued in the afternoon. The hard work paid off. Finally, at about 3 pm, we encountered the same fault as reported by the residents. When we saw the change between the PLC points and the contactor in the machine room when the fault occurred, it turned out that it was caused by a defect in the safety circuit. We immediately checked the drawings and all the safety circuit switches in the shaft and the machine room. We found that all the switches were fine, and the contactor and relay wiring were normal. Then we checked it carefully against the electrical drawings and found that a switch was missing, that is, there was a contact in the frequency converter. What caused the frequency converter failure? Suddenly I remembered that when I checked the strong deceleration switch, I found that the position of the deceleration switch had changed, so I went down to check it in time and found that the switch moved downward. The elevator moved as much as 10cm, and then I understood why the elevator always ran to the first floor and then automatically reset after closing the door.

It turned out that because the switch position dropped, the signal detected by the encoder during operation was different from the original setting. It began to protect after the accumulated error reached a certain data. After the safety circuit was powered off, the running contactor was cut off, so the inverter was also powered off, and the fault in the inverter was automatically reset. Since the inverter automatically reset and the safety circuit was normal, the elevator resumed normal operation after arriving at the scene. So the switch was restored to its original position, and then the elevator was re-learned in the machine room, so that the elevator could run at high speed. After repeated speculation, careful investigation, and repeated operation by the repairman, the elevator finally worked healthily and safely, ensuring the normal life of the owner.

3. Otis Elevator 5LS multi-layer strong deceleration switch function failure

A certain residential area has a Hangzhou Xizi Otis 300VF elevator with 18 floors and 18 stations. A resident reported that "when he was taking the elevator home today, the elevator suddenly stopped at the top floor. After opening the door, he found that the elevator was about 10cm higher than the flat area. He was scared and quickly escaped and called the management office to report the repair."

After receiving the emergency repair report from the community management office, the repairman quickly rushed to the scene and found that the elevator was operating normally and did not stop at the top floor as reported by the residents. The repairman entered the car and tested it from the first floor to the top floor. He ran up and down several times and found no abnormality. So he went to the machine room again and retrieved all the fault records of the elevator that day through the Otis dedicated server. The fault codes recorded by the server were 2101, 2109, and 2700. 2101 was judged to be an error in the elevator position measured by the elevator detection system, 2109 was an error in the elevator's strong deceleration switch detected by the computer board, and 2700 was a DBSS fault or brake fault. After comprehensive analysis of the server's fault records, we first checked the brake circuit in the computer room and found that the contact points of each contactor were in good contact, the brake was flexible to open, and the gap met the requirements. We checked in the well and measured the resistance of 6LS (single-layer upward strong deceleration switch) and 5LS (multi-layer upward strong deceleration switch) with a multimeter. The former was normal, and the latter was that the 5LS resistance was slightly overvalued. We dealt with it and cleared the computer board fault in the computer room. We left the scene and reported the situation to the community management office.

A week later, the community management office called again and said that the elevator had broken down again. The last time it was reported by the owner of Room 1801. Today, the owner of Room 1803 called to report the problem, saying that "the elevator often stops suddenly after reaching the top floor when I take the elevator home these days. After opening the door, I found that the elevator was much higher and it seemed that there was no leveling."

After receiving the repair report, the maintenance personnel rushed to the scene immediately. We found that the elevator was still running. We took the elevator to the top floor, the 18th floor. Everything was normal. So I asked the owner of Room 1803 to talk about the recent malfunction of the elevator. The owner said that recently the residents on the 18th floor found that the elevator stopped suddenly many times when it came up, but the elevator automatically returned to normal after a while. He always came up from the 1st floor and stopped suddenly when he reached the 18th floor. Every time he came out, the elevator threshold was much higher than the floor. After listening to the residents' feedback, we went to the elevator room and used the server to call up the fault code. We found that it was the same as the last fault code. This time, two maintenance personnel divided the work. One person watched the fault phenomenon displayed on the server when the fault occurred in the machine room, and the other person went to the car and kept driving up and down, from the 1st floor to the 18th floor, without stopping in the middle floors, driving down and observing up, and finally observed the working conditions of 6LS and 5LS through the server. After more than 2 hours of continuous operation, we finally encountered the fault phenomenon as described by the residents. The Otis server showed LS-Fauit, which means "the up and down strong deceleration is not working properly". At the same time, we also saw on the server that 5LS did not work at that time. Everyone finally understood. Because 5LS is a multi-layer strong deceleration, it was found that its resistance value was slightly overvalued. Although it was processed, it was still not solved. When the elevator went directly from the 1st floor to the top floor, it was high-speed operation. Because the 5LS strong deceleration switch sometimes had poor contact, it could not decelerate in advance. When 6LS worked, it was too late to decelerate. The elevator hit the upper limit and stopped suddenly. Because we were in the flat area, the elevator opened the door after emergency stop, and no one was trapped. The elevator could not run upwards, but it could run normally downwards, so every time we passed by, the elevator was in normal use. After finding the fault point, we immediately replaced the 5LS strong deceleration switch. The elevator has been running for a long time without similar faults. The fault that had been bothering the maintenance unit and the property management office for a long time was eliminated.

With the rapid development of science and technology, as the main means of vertical transportation in buildings, the technological content of elevators is constantly improving, and the functional requirements of safety, comfort, energy saving and speed are becoming more and more perfect. At the same time, the technical requirements for installation, maintenance and management are becoming more and more stringent. The elevator terminal deceleration control system is only a small subsystem in the field of elevator machine and electrical system. It seems that the principle is relatively simple, but if a fault occurs, it is sometimes difficult to repair, which will also affect the overall situation. The above three elevator failure cases are enough to illustrate the problem. In order to ensure the normal operation of various types of elevators, the installation, maintenance and management of elevators must be meticulous, and each link must be closely linked. While ensuring the quality, management personnel and maintenance technicians must be familiar with the mechanical and electrical principles of the elevator and fully "digest" them. Only in this way can the elevator be guaranteed to operate healthily and safely for a long time.