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Safety circuit
Function: To ensure the safe operation of the elevator, many safety components are installed on the elevator. The elevator can only operate when every safety component is in normal condition, 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, connecting all safety switches in series to control a safety relay. Only when all safety switches are turned on and the safety relay is engaged, can the elevator be powered on and run.
Common safety circuit switches include:
Computer room: control screen emergency stop switch, phase sequence relay, thermal relay, speed limiter switch
Shaft: upper limit switch, 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: control box emergency stop switch
Car roof: safety window switch, safety clamp 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. The first suspicion is a safety circuit malfunction. 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 of the input power supply is incorrect or there is a missing phase, causing the phase sequence relay to operate.
2. The elevator has been operating at overload or stuck for a long time, causing the thermal relay to activate.
3. The overspeed of the speed limiter may cause the speed limiter switch to operate.
4. The elevator's top or bottom impact causes the limit switch to operate.
5. The pit rope switch is activated. It may be due to the speed limiter rope jumping out or being too long.
6. Action of safety pliers. The cause should be identified. It may be due to overspeed action of the speed limiter, misoperation of the speed limiter due to oil loss, oil loss of the pit pulley, foreign objects (such as mice) being caught in the pit pulley, or too small a gap between the 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.
If all switches are normal, check whether their contacts are in good contact and whether the wiring is loose.
In addition, although the safety circuit of many elevators is normal and the safety relay is also closed, a normally open contact is 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 fault in the safety circuit.
Door lock circuit:
effect:
To ensure that the elevator can only operate after all doors are closed, door electrical interlock switches are installed on each hall door and car door. Only when all the electrical interlocking switches of the doors are fully connected, can the door lock relay of the control screen be activated and the elevator operate.
Fault status:
When all doors are closed, observe the status of the door lock relay on the control screen. If the door lock relay is in the released state, it should be judged that the door lock circuit is disconnected.
Repair method:
Due to the fact that most elevators currently cannot operate both fast and slow trains when the door lock is disconnected, although it is easy to determine the door lock fault, it is difficult to identify which door is faulty.
My repair suggestion:
Firstly, it is important to suspect whether the door lock on the elevator stop floor is faulty.
2. Ask if there is a triangular key to open the landing door, and use the triangular key outside the hall to reopen and close the hall door.
3. Ensure that during maintenance, short-circuit the hall door lock and hall door lock separately on the control screen, and distinguish whether the fault is in the hall door or the car door.
4. If there is a malfunction in the hall door, ensure that the hall door lock circuit is short circuited during maintenance, and operate the elevator at maintenance speed. Check the interlocking contact of each hall door layer by layer (don't forget the passive door).
Attention: After repairing the door lock circuit fault, it is necessary to first remove the door lock short-circuit wire in order to restore the elevator to express mode.
In addition, although the door lock circuit of many elevators is normal and the door lock relay is also engaged, a normally open contact is usually taken from the door lock relay and sent to the microcomputer (or PC) for testing. If the door lock relay itself has poor contact, it can also cause a fault in the door lock circuit.
Safety touch panel (door photoelectric, door light curtain)
effect:
In order to prevent elevator doors from trapping passengers during the closing process, safety touch panels (or photoelectric or light curtains) are generally installed on elevator car doors
Safety contact plate: It is a mechanical anti pinch device. When a person touches the safety contact plate during the elevator door closing process, the safety contact plate will retract inward, driving a micro switch at the lower part. The safety contact plate switch will act, controlling the door to rotate in the direction of opening.
Optoelectronics: Some elevators are equipped with door photoelectric devices (at least two points are required), with one side as the transmitting end and the other side as the receiving end. When the elevator door is closed, if there is an object blocking the light and the receiving end cannot receive the light source from the transmitting end, the photoelectric relay will be immediately activated to control the door to open in the opposite direction.
Light curtain: Similar to the principle of optoelectronics, it only has many emission and reception points.
Fault status:
The elevator door cannot be closed
Phenomenon: The elevator cannot be closed when in automatic mode, or it opens in reverse before being fully closed. It can be closed during maintenance.
Reason: The safety touch panel switch is broken, stuck, or improperly adjusted, and a slight movement of the safety touch panel can cause the switch to operate. The position of the door photoelectric (or light curtain) is offset or obstructed. There is no power supply for the door photoelectric (light curtain), or the photoelectric (light curtain) is broken.
The safety touch panel is not functioning
Reason: The safety touch panel switch is broken or the wire has been disconnected.
Repair: After identifying the cause, repair it.
Closing force limit switch
effect:
Some elevator doors are equipped with door force limit switches. If the door still cannot be closed due to certain resistance during the closing process, the switch will activate and the door will rotate in the direction of opening.
Although some variable frequency door machines do not have this switch, they still have similar functions. If there is a certain resistance when closing the door, and the current of the door motor exceeds a certain value calculated by the frequency converter and still cannot be closed, it will be opened in the opposite direction
Fault state: When the door closing force limit switch malfunctions, the door will never close.
Door opening and closing button
effect:
When in automatic mode, if the door opening button is pressed and held, the elevator door will remain open for a long time, making it convenient for passengers to enter and exit the car normally when there are many passengers.
Pressing the door close button will immediately close the door. During maintenance, it is used to control the opening and closing of elevator doors.
Fault phenomenon:
Sometimes the door opening and closing button gets stuck inside and cannot pop out after being pressed. If the door opening button gets stuck, it may cause the rear door of the elevator to remain open and unable to close. The door closing button getting stuck can cause the rear door to not open upon arrival.
Identify the cause and ensure that the button action is flexible and reliable.
Call button outside the hall
effect:
The call button outside the hall is used to register the elevator needs of passengers outside the hall. At the same time, it has the function of opening doors in the same direction on this floor. If the elevator is running upwards and the up call is held down, the elevator door will remain open for a long time. Some elevators are designed to forcibly close after a certain period of time.
Fault phenomenon:
Sometimes when the call button gets stuck, the elevator will stop on this floor without closing the door. Or after a certain period of time, it may be forced to close the door and then run towards that level for a period of time each time.
repair:
Identify the cause and ensure that the button action is flexible and reliable.
Door machine system
1. DC gantry crane system
Working principle analysis:
Opening the door: When JKM is engaged, the current flows through both the motor rotor DM and the door opening resistor RKM, from M2 to M3, causing the door machine to rotate in the direction of opening the door. At this time, the resistance value of RKM is relatively high, and the shunt through RKM is small. So the door opening speed is faster. When the elevator door is closed to 3/4 of its travel distance, the deceleration limit of the switch is set to 1KM, which short circuits most of the resistance of the RKM and increases the shunt through the RKM, thereby reducing the motor speed and achieving the deceleration function of opening the door. When the door opening is completed, cut off the door opening interruption limit, release the door opening relay, and stop the elevator from opening the door.
Closing the door: When JGM is closed, the current passes through both DM and the closing resistor RGM, from M3 to M2, causing the door machine to rotate in the direction of closing the door. Because the resistance value of the RGM is relatively high at this time, the shunt through the RGM is small, resulting in a faster closing speed. When the elevator is halfway closed, the first level deceleration limit of 1GM is connected to short-circuit a part of the resistance of RGM, increasing the shunt from RGM and achieving first level deceleration of the door machine. When the elevator door continues to close to 3/4 of the trip, connect the second level deceleration limit 2GM and short-circuit most of the RGM resistors to further increase the shunt from the RGM
The speed of the door machine is further reduced, achieving a two-stage deceleration for closing the door. When the door is closed, cut off the door closing terminal limit, release the door closing relay, and stop the elevator from closing the door.
By adjusting the total voltage resistor RMD in the switch gate circuit, the overall speed of the switch gate can be controlled.
Because when JY is engaged, the excitation winding DMO of the door machine is always energized, so when JKM or JGM is released, the motor can immediately enter energy consumption braking and the door machine will stop immediately. And when the elevator door is closed, it can provide a braking force to ensure that the elevator door cannot be easily opened inside the car.
Common faults in DC gantry crane systems:
Phenomenon 1: The elevator does not slow down when opening the door. There is a sound of impact.
reason:
When the door is opened, the deceleration limit cannot be reached.
The deceleration limit for opening the door is broken and cannot be connected.
The door deceleration resistor has burned out or the middle clamp has poor contact with the resistance wire.
Phenomenon 2: The elevator does not slow down when closing the door, and there is a collision sound when closing the door quickly
reason:
When the door is closed, the deceleration limit cannot be reached.
The deceleration limit for closing the door is broken and cannot be connected.
The door closing deceleration resistor has burned out or the middle clamp has poor contact with the resistance wire.
Phenomenon 3: The speed of opening or closing the door is too slow.
Reason: The deceleration limit for opening or closing the door is broken and is in a normally connected state.
Phenomenon 4: The door cannot be closed but can only be opened (JKM and JGM operate normally)
Reason: It may be that the door closing terminal limit is broken and always in a disconnected state.
Phenomenon 5: The door cannot be opened and can only be closed (JKM and JGM operate normally)
Reason: It may be that the door opening terminal limit is broken and always in a disconnected state.
Phenomenon 6: The door cannot be opened or closed (JKM and JGM operate normally)
Reason: It may be that the total resistance of the door has burned out.
2. VVVF Variable Frequency Door Machine System
Most elevators produced now use VVVF variable frequency door system. In a typical variable frequency door system, the control panel provides a power supply, an opening signal, and a closing signal to the door system.
Variable frequency door machine systems also have deceleration switches and terminal switches, mostly using bistable magnetic switches. The door system has self-learning function. When the terminal switch of the door machine is activated, a terminal signal is returned to the control screen to control the opening and closing of the door relay.
Generally, variable frequency door machines can be set for door opening and closing speed, torque, deceleration point position, etc. Specific adjustments should refer to the door machine system manual or elevator debugging data provided by the manufacturer.
Some variable frequency door machines lose their open position signal after turning on the car door due to power failure. The door machine will no longer be controlled by the control screen's door opening and closing signals, and must self learn once after power failure before it can work normally.
Some variable frequency door machine systems, in addition to being controlled by the control screen's door opening and closing signal, have their own power limit calculation function. When the power limit exceeds the set value during the door closing process, it will open in the opposite direction. This force limit calculation only becomes invalid when the closing terminal switch is activated. For this type of door system, the position of the door closing terminal must be ahead of the car door lock. Otherwise, the elevator can run after the door lock is connected. If this force limit calculation is still valid, it may cause the elevator to open the door during operation, and attention should be paid. (I personally think this design is unreasonable. The door system must always be controlled by the control screen and cannot be self-contained.)
Limit of upper and lower terminals in the shaft
effect:
The upper terminal limit usually operates when the elevator reaches the highest floor and is 5-8CM above the ground level. After the action, both the fast and slow trains of the elevator cannot run upwards anymore.
On the contrary, the lower terminal limit usually operates when the elevator reaches the bottom floor and is 5-8CM below the level. After the action, both the fast and slow trains of the elevator cannot continue to run downwards.
Fault phenomenon 1: Both the fast and slow trains of the elevator cannot run upwards, but can run downwards.
Reason: It may be due to a faulty upper terminal limit, which is in a disconnected state.
Fault phenomenon 2: Both the fast and slow trains of the elevator cannot run downwards, but can run upwards.
Reason: It may be due to a faulty lower terminal limit, which is in a disconnected state.
Forced deceleration limit up and down the shaft:
Elevators with speeds below 1 meter per second are generally equipped with an upward forced deceleration limit and a downward forced deceleration limit. The installation location should be equal to (or slightly less than) the deceleration distance of the elevator. Elevators with a speed of 1.5 meters per second or higher are generally equipped with two upward forced deceleration limits and two downward forced deceleration limits. Because fast elevators are generally divided into two types: single-layer operating speed and multi-layer operating speed, and the deceleration distance varies at different speeds, they need to be divided into multi-layer operating deceleration limit and single-layer operating deceleration limit.
Function 1: Force the elevator to enter deceleration operation when it reaches the end station.
Function 2: Currently, many elevators use forced deceleration limit as a forced correction point for elevator floor position.
Fault phenomenon 1: The express train of the elevator cannot run upwards, but the slow train can.
Reason: It may be that the upward forced deceleration limit is broken and in a disconnected state.
Fault phenomenon 2: The fast elevator cannot run downwards, but the slow elevator can.
Reason: It may be that the upward forced deceleration limit is broken and in a disconnected state.
Fault phenomenon 3: The elevator is in a faulty state and the program is activated for protection. It may be displayed as a speed switch fault using a fault code.
Reason: It may be that the upward or downward forced deceleration limit is broken. Due to the significant importance of forced deceleration limit in elevator safety, many elevator programs are designed with a detection function for this limit. If the limit is detected to be faulty, program protection will be activated. The elevator is in a 'crash' state.
Layer selector
Function: Calculate the actual position of the elevator during operation.
Type of Layer Sorter: Mechanical Layer Sorter
Early elevators used mechanical floor selectors, some using synchronous steel strips, and some using running lights, to follow the operation of the elevator and simulate the actual position of the elevator.
2. Shaft floor sensor
Some elevators calculate the elevator position by installing a magnetic sensor on each floor in the shaft and a magnetic isolation plate on the side of the car. When the magnetic isolation plate is inserted into the sensor, the sensor will activate, and the control screen will immediately calculate the actual position of the elevator upon receiving the signal from the sensor. Simultaneously control the display to show the floor number of the elevator's location.
Fault phenomenon:
To determine the direction of operation of an elevator, it is necessary to know the current location of the elevator, so the determination of the elevator's position is very important. If this part of the circuit fails, the elevator may not be able to automatically determine the direction of operation, and there may be a phenomenon of signal registration failure.
Similarly, when this part of the circuit malfunctions, it usually causes phenomena such as incorrect floor display numbers. (Please take a detailed look at the floor control and automatic directional parts of the relay elevator)
3. Car speed sensor
At present, some elevators omit floor sensors and use speed sensors installed on the elevator car to calculate floors. (such as in a housing factory).
This type of elevator is equipped with an up speed sensor and a down speed sensor on the car side, and a short magnetic barrier is installed at the up speed point and down speed point of each floor stop in the shaft.
When the elevator goes up and reaches the speed change point, the magnetic barrier is inserted into the sensor, and the sensor is activated. The control screen receives a signal, causing the original number of floors to automatically increase by 1.
When the elevator descends and reaches the speed change point, a magnetic barrier is inserted into the sensor, which activates. The control screen receives a signal, causing the original number of floors to automatically decrease by 1.
When the elevator reaches the bottom floor, the downward forced deceleration limit action can force the elevator floor number to be converted to the lowest floor number.
When the elevator reaches the highest floor, the upper forced deceleration limit action can force the elevator floor number to be converted to the highest floor number.
Fault phenomenon:
This type of elevator often causes chaos during operation.
For example, when the speed sensor of the elevator is broken (unable to operate), the number will not flip when the elevator is running upwards, and it cannot stop at the designated floor. Instead, it will continue to run upwards quickly until it reaches the highest floor, and the floor number will flip to the highest floor at once. Make the elevator slow down and stop at the highest floor.
4. Digital layer selector
The so-called digital layer selector is actually a device that calculates floors using the number of pulses obtained from a rotary encoder. This is quite common in most variable frequency elevators currently.
Principle:
The rotary encoder installed on the tail end (or speed limiter shaft) of the motor rotates synchronously with the electric power. For each rotation of the motor, the rotary encoder can emit a certain number of pulses (usually 600 or 1024).
After the installation of the elevator is completed, it is generally necessary to perform a floor height writing operation. This step involves storing the height pulse number and deceleration distance pulse number of each floor in the computer in advance. In the future, the running pulse number of the rotary encoder is compared with the stored data to calculate the position of the elevator.
Generally, a rotary encoder can also obtain a speed signal, which needs to be fed back to the frequency converter to adjust the output data of the frequency converter.
Fault phenomenon:
When the rotary encoder is broken (no output), the frequency converter cannot work normally, and the running speed becomes very slow. In addition, after a while, the frequency converter is protected and displays information such as "PG disconnected".
When the grating of the rotary encoder is damaged, pulses will be lost during operation, and there will be vibrations during elevator operation, resulting in poor comfort.
repair:
The wiring of the rotary encoder should be secure, and the wiring should be separated from the power line to prevent interference.
Sometimes, due to contamination of the rotary encoder or blockage of the grating, the casing can be disassembled for cleaning.
be careful:
Rotary encoders are precision electromechanical integrated equipment, so be careful when removing them.
Elevator car upper and lower level sensors
effect:
Used for climbing and leveling the elevator car
Used for feedback gate area signals
Fault phenomenon:
When the leveling sensor does not operate (or the position deviation of the magnetic plate inserted into the sensor is too large), the elevator may not level after deceleration,
But continue to drive slowly.
Some elevator programs can detect the movement of the leveling sensor. For example, when the elevator is running rapidly, it is required to detect a leveling signal at a certain time. Otherwise, it is considered that the sensor is in error, and the program immediately feeds back the elevator fault signal.
load cell
effect:
Used to measure the load capacity of elevators and send signals such as light load, full load, and overload. Some can provide compensation during elevator operation. Cooperate with anti disturbance functions, etc.
Fault phenomenon:
Mainly to prevent the position of the weighing device from shifting and causing misoperation. At this point, it is necessary to conduct a new experiment and adjust the position. Otherwise, it may cause elevator crashes and other situations.
