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Elevator Knowledge Elevator Electrical Control System Fault Maintenance Experience Sharing
Apr 26, 2018

According to statistics, in the elevator accident, electrical accidents accounted for more than 80% of the total elevator accidents. It is very necessary to prevent elevator electrical accidents and do related maintenance work. Then we learn about some of the causes of the failure of the elevator control system, and related processing methods to ensure the safe and reliable operation of the elevator.



Safety circuit

   Role: To ensure that the elevator can operate safely, there are many safety components on the elevator. Only if each safety component is in normal condition, the elevator can run, otherwise the elevator will immediately stop running.

    Common safety circuit switches are:

    Room: Control panel emergency stop switch, phase sequence relay, thermal relay, speed limiter switch

    Well: Upper limit switch, lower limit switch

    Ground pit: broken rope protection switch, pit maintenance box emergency stop switch, buffer switch

    Car: Control Box Emergency Stop Switch

    Car top: safety window switch, safety gear switch, car top repair box emergency stop switch

    Fault status: When the elevator is in a stop state, all signals cannot be registered, and neither the fast train nor the slow train can operate. First, it is suspected that the safety loop is faulty. The status of the safety relay should be observed on the control panel of the equipment room. If the safety relay is released, it should be judged as a safety circuit failure.

    Possible causes of failure:

    1. The phase sequence relay is activated due to the wrong phase sequence or phase loss of the input power supply.

    2. The elevator is in overload operation or stalled for a long time, causing the thermal relay to move.

    3. Overspeed may cause overspeed governor switching.

    4. Lifting or sinking of the elevator causes extreme switching.

    5. The pit breaks the rope switch action. Maybe the speed limiter rope jumps out or is too long.

    6. Safety pliers action. Should find out the reason. Possible speed limiter overspeed action, overspeed governor oil loss error, oil loss in the pit rope, foreign objects (such as rats, etc.) in the pit rope, and gaps in the safety stake are too small.

    7. The safety window is lifted up, causing the safety window to open and close.

    8. Possible emergency stop switch was pressed.

    9. If all switches are normal, check for good contact and loose connections.

Door lock circuit

    Role: In order to ensure that the elevator can only operate after all doors are closed, a door electric interlock switch is installed on each hall door and car door. Only when all the electrical interlock switches of the door are fully connected, the door lock relay of the control panel can only pull in and the elevator can run.

    Fault status:

    When all the doors are closed, the state of the door lock relay is observed on the control panel. If the door lock relay is in the release state, it should be judged that the door lock circuit is open.

    Repair suggestions:

    1. First, it is important to doubt whether the door lock of the elevator stop layer is faulty.

    2. Ask if there is a triangular key to open the landing door and use the triangle key to re-open the hall door outside the hall.

    3. Make sure that in the inspection state, the control panel separates the shortroom door lock and the hall door lock, and it is determined whether the hall door part or the car door part is faulty.

    4. If the hall door is partially faulty, ensure that under the overhaul condition, the short-circuit hall locks the loop, run the elevator at the inspection speed, and check the contact status of each hall door by layer (don't forget the passive door).

    Note: After repairing the door lock loop fault, it is necessary to remove the short wiring of the door lock before it can restore the elevator to the fast state.

    In addition, at present, although many lifts have a normal door lock circuit and the door lock relay also pulls in, they usually take a normally open contact on the door lock relay and send it to the PC (or PC) for detection. If the door lock relay itself contacts, Bad, it will also cause the state of the door lock circuit failure.

Security touch panel (door photoelectric, door light curtain)

    Role: In order to prevent the elevator door from catching passengers during the closing process, a safety touch panel (or photoelectric or light curtain) is generally installed on the elevator car door.

    Fault status:

    1. Elevator door is not closed

    Phenomenon: The elevator cannot be turned off when it is in automatic position, or reversed when it is not turned off. It can be closed during inspections.

    Causes: The safety touch panel switch is broken, or it is stuck, or the switch is improperly adjusted. The safety switch touches the switch slightly when it is actuated. The door optoelectronic (or light curtain) is offset or blocked. Or door photoelectric no (light curtain) power supply, or photoelectric (light curtain) has been broken.

    2. Security touchpad does not work

    Cause: The safety touch switch is broken or the wire is broken.

    Repair: Repair after finding out the reason.

Closed limit switch

    Function: Some elevator doors are equipped with door limit switches. If the door is closed during the closing process, if it is subject to a certain resistance, the switch will move and the door will rotate in the direction of opening the door.

    Some frequency conversion door machines do not have this switch, but they have similar functions. If there is a certain resistance when the door is closed, it cannot be closed when the inverter calculates the door machine current exceeds a certain value, and it opens in the opposite direction.

    Fault condition: The door will always fail to close when the door closing force limit switch malfunctions.

Door system

    1. Analysis of working principle of DC door machine system:

    Open the door: When the JKM pulls in, the current passes through the motor rotor DM on the one hand and from the M2 → M3 via the open resistor RKM on the other hand, which causes the door machine to rotate in the direction of opening the door because the RKM resistance is larger and the shunt is distributed through the RKM. Smaller. So the door opening speed is faster. When the elevator door is closed to the 3/4 trip, the switch deceleration limit 1KM is switched on, most of the RKM resistances are shorted, the shunt through the RKM is increased, so that the motor speed is reduced, and the deceleration of the door is realized . When the door is opened, the limit of opening the door is cut off, so that the door opening relay is released and the elevator stops opening the door.

    Closed: When the JGM pulls in, the current passes through the DM on the one hand, and passes through the door closing resistor RGM on the other, from M3 → M2, causing the door machine to rotate in the direction of closing the door. Because the RGM resistance is larger at this time, the shunt through the RGM is smaller, so the closing speed is faster. When the elevator is closed to half of the journey, the first-level deceleration limit 1GM of the door closing is closed, a part of the resistance of the RGM is shorted, and the partial flow from the RGM is increased, and the door machine realizes a first-order deceleration. When the elevator door continues to close to the 3/4 journey, it connects the 2nd deceleration limit 2GM, short-circuits most of the resistances of the RGM, further increases the diversion from the RGM, and the elevator door machine rotation speed further reduces, achieving the closed-door secondary slow down. When the door closes, the limit of the closing door is cut off, the door closing relay is released, and the elevator stops closing.

    By adjusting the total voltage divider resistance RMD in the switch gate circuit, the overall speed of the opening and closing door can be controlled.

    Because when the JY pulls, the door machine excitation winding DMO is always charged, so when the JKM or JGM is released, the motor can immediately enter the energy consumption brake, and the door machine stops immediately. And when the elevator door is closed, it can provide a braking force to ensure that the elevator door cannot be easily opened in the car.

    Common faults in DC gated systems:

    Phenomenon 1: There is no deceleration to open the elevator door. There is a crash.

    the reason:

    1. The door opening deceleration limit cannot be reached when the door is opened.

    2. The door open deceleration limit is bad and cannot be connected.

    3. The door opening deceleration resistor has been blown or the middle clamp and the resistance wire are in poor contact.

    Phenomenon 2: There is no deceleration when the elevator is closed, there is a quick knocking

    the reason: 

    1. The door closing deceleration limit is not reached when the door is closed.

    2. The door closing deceleration limit is bad and cannot be connected.

    3. The door closing deceleration resistor is blown or the middle clamp and the resistance wire are in poor contact.

    Phenomenon 3: The speed is too slow when opening or closing.

    Reason: The speed limit for opening or closing the door has been broken and is in the normally connected state.

    Phenomenon 4: The door cannot be closed but only open (JKM and JGM operate normally)

    Cause: It may be that the terminal limit of the door has been broken and it is always in the disconnected state.

    Phenomenon 5: The door cannot be opened and closed (JKM and JGM are operating normally)

    Reason: It may be that the terminal limit of the door has been broken, and it is always in the disconnected state.

    Phenomenon 6: The door cannot be opened or closed (JKM and JGM operate normally)

    Cause: It may be that the total resistance of the door has blown.

    2. VVVF frequency conversion door machine system

    Most of elevators produced now use the VVVF inverter door control system. In the general inverter door control system, the control panel provides a power supply for the door machine system, a door opening signal, and a door closing signal.

    Frequency conversion door machine systems also have deceleration switches and terminal switches, most of which use bistable magnetic switches. The door machine system has a self-learning function. When the door operator terminal switch is actuated, a terminal signal is returned to the control panel to control the door relay.

    General frequency conversion door machine can be used to set the opening and closing door speed, torque, deceleration point, etc. The specific reference should be made to the door machine system manual provided by the manufacturer or the elevator commissioning data for adjustment.

    Some frequency conversion door machines lose the signal because of the open position after the power is turned off. The door machine will no longer be controlled by the control panel switch door signal. It must be self-learning after power off before it can work normally.


Well upper and lower terminal limit

    Function: The upper limit of the terminal is generally at the highest level of the elevator, and operates at 5-8CM above the leveling floor. After the action, the elevator express and local trains can no longer operate upwards. On the other hand, the lower terminal limit is generally at the bottom of the elevator and is below the level of 5-8CM. After the action, the elevator express and local trains can no longer run down.

    Symptom 1: The elevator and local trains cannot run upward but they can run downwards.

    Cause: The upper terminal limit may be bad and is in a disconnected state.

    Symptom 2: Both elevators and local trains cannot run downwards, but they can run upwards.

    Cause: The lower terminal limit may be bad and is in a disconnected state.

Shaft forced up and down limit

    Elevators with a speed of 1 m/s or less generally have 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. Elevators with a speed of 1.5 m/s or more are generally equipped with two upward forced deceleration limits and two downward forced deceleration limits. Because fast elevators are generally divided into single-layer operation speeds and multi-layer operation speeds, the deceleration distances are not the same at different speeds, so it is necessary to divide the multi-layer operation deceleration limit and single-level operation deceleration limit.

    Function 1: Force the elevator to decelerate when the elevator runs to the end station.

    Role 2: At present, many elevators use the forced deceleration limit as the forced correction point of the elevator floor position.

    Symptom 1: The elevator train cannot run upwards, but the local train can.

    Reason: It may be that the forced deceleration limit is broken and is in the disconnected state.

    Symptom 2: The elevator express cannot run down, but the local train can.

    Reason: It may be that the forced deceleration limit is broken and is in the disconnected state.

    Symptom 3: The elevator is in a fault state and the program is protected. It may be displayed as fault switch fault with fault code.

    Cause: It may be that the forced deceleration limit has been broken up or down. Because the forced deceleration limit is very important in the safety of elevators, many elevator programs are designed to detect the limit. If the limit is detected, the program is protected. The elevator is in a "dead" state.

Selector

    Role: Calculate the actual position of the elevator in operation.

    Selector type:

    1. Mechanical selector

    The earlier elevators used mechanical selectors, some of which used synchronous steel belts, some of which used go walkers. Following the operation of the elevator, the simulation reflected the actual position of the elevator.

    2, well floor sensor

    In some elevators, the position of the elevator is calculated by relying on a magnetic sensor on each floor of the hoistway, and a magnetic separation board is installed on the side of the car. When the magnetic separation board is inserted into the sensor, the sensor moves and the control panel receives this. Immediately after the signal from the sensor, the actual position of the elevator is calculated. At the same time, the control display shows the floor number of the elevator.

    Fault phenomenon:

    In order to determine the direction of operation, the elevator must know where the elevator is currently located. Therefore, the determination of the elevator's position is very important. This part of the circuit has a fault, and the elevator may not automatically determine the direction of operation, and the phenomenon of signal registration may not occur. . In the same way, when this part of the circuit fails, it will generally cause incorrect display of floor numbers. (Please take a closer look at the floor control part and automatic orientation part of the relay elevator)

    3, car speed sensor

    At present, some elevators eliminate the floor sensors and use the speed change sensors installed on the cars to calculate floors. (such as a house plant).

    This elevator is equipped with an on-speed sensor and a down-speed sensor on the side of the car, and a short magnetic separator is installed at each of the up and down-change points at each stop of the hoistway. board.

    When the elevator goes up, when it reaches the speed change point, the magnetic board is inserted into the sensor and the sensor moves. The control panel receives a signal, which automatically increases the original floor number.

    When the elevator goes down, when it reaches the speed change point, the magnetic board is inserted into the sensor and the sensor moves. The control panel receives a signal, which automatically reduces the original number of floors by 1.

    When the elevator reaches the bottom floor, when the forced deceleration limit is actuated, the number of elevator floors can be forced to the lowest floor number.

    When the elevator reaches the top floor, when the forced deceleration limit action is performed, the elevator floor numbers can be forced to be converted to the highest floor number.

    Fault phenomenon:

    This type of elevator often causes the elevator to run in a mess.

    For example, when the speed change sensor is bad (cannot act), when the elevator is running upwards, the number will not be reversed, nor will it stop at the designated floor. Instead, it will run up to the highest level and the floor number will turn to the highest level. Make the elevator stop at the highest level.

    4, digital selector

    The so-called digital selector is actually a device that uses the number of pulses obtained by a rotary encoder to calculate floors. This is more common in most current inverter elevators.

    principle:

    The rotary encoder mounted on the tail end of the motor (or the speed limiter shaft) rotates synchronously with the electromotive force. With one revolution of the motor, the rotary encoder can emit a certain number of pulses (generally 600 or 1024).

    After the installation of the elevator is completed, a floor height writing operation is generally performed. This step is to store the height pulse number and the deceleration distance pulse number of each floor in advance into the computer. In the subsequent operation, the operation of the rotary encoder is performed. The number of pulses is then compared with the stored data to calculate where the elevator is located.

    In general, a rotary encoder can also obtain a speed signal, which is fed back to the frequency converter to adjust the output data of the frequency converter.

    Fault phenomenon:

    1. When the rotary encoder is broken (no output), the inverter cannot work normally and it becomes very slow, and


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