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National elevator high temperature warning, strengthen the heat to let the elevator heatstroke
Jul 30, 2018

Look at the temperature of the elevator host and control cabinet


    "High-temperature weather elevator safety use tips" reminds the elevators to use the unit, during the high temperature period, it is necessary to strengthen the ventilation, sunshade and cooling of the elevator machine room, sightseeing elevator shaft and car.


    What happens to the elevator "heatstroke"?


    Cause damage to parts,


    Easy to sleep or the button is out of order!


    “Once the temperature of the equipment room is too high, it is easy to cause damage to parts.” An elevator maintenance staff told reporters that the elevator room has long-term high-temperature operation, which is easy to cause circuit failure. For example, the elevator door suddenly cannot open, people are trapped in the elevator, and the elevator The button is out of order, the elevator suddenly loses power, etc. "These are the performances of the elevator being 'hot"."


    The elevator maintenance staff of Xiacheng University City of Xiamen University also said that they can receive more than 40 maintenance calls a month, especially in the summer. "In high temperature weather, the elevators are indeed more faulty than usual, and the time is the highest. “The maintenance personnel said that the elevator was “hot” and it was easy to crash, and such accidents occurred in the elevator room where air conditioning was not installed. In addition, some computer rooms have automatic sensing systems. When the "high fever" is above 40 °C, they will be automatically disconnected, which will stop the elevator from operating. "There are unexpected accidents such as trapped people and power outages."


    In order to avoid the elevator being "heated", the new elevators have their own cooling fans, and the old elevators have poor heat dissipation capacity. Therefore, the property generally installs air conditioners spontaneously, lowers the temperature of the equipment room, and air conditioners 24 when the weather is hot and humid. Opened in hours, "In general, the overall temperature of the equipment room is kept at 40 °C, which plays a role in cooling and dehumidification."


    How to give the elevator "cooling down"?


    Air conditioning in the computer room for 24 hours


    Regular inspection during peak hours


    Yesterday afternoon, the reporter came to the elevator machine room on the west side of the top floor of the newspaper building. It was very cool inside. Between the two control cabinets and the two traction machines in the machine room, there is a cabinet type air conditioner with a height of about 1.8 meters. The air conditioner has been driven to the maximum, and the indoor temperature on the display is 25 °C. Mr. Li, the director of Haiyi Property Engineering Department, told the reporter that due to the large thermal energy generated during the operation of the air conditioner, the elevator engine room is on the top floor, and the top floor is poorly insulated. Therefore, since the temperature of the elevator is too high, since the end of April this year, it has entered the rainy season. The property will open the air conditioning in the computer room for 24 hours.


    The reporter followed the on-duty personnel to the elevator room in the east, and happened to encounter the air conditioner in this elevator room. As soon as the reporter entered the door, a heat wave hit and the property staff turned on the air conditioner. At this time, the air conditioner screen showed that the indoor temperature had reached 37 °C. The duty officer told the reporter that the air conditioner in the summer is also faulty. Therefore, in order to avoid overheating of the equipment room, in addition to regular maintenance at half a month, every hour during the peak hours from 10 am to 5 pm every day, someone will go upstairs to inspect once. .


    Weapon


    What if I am trapped in an elevator?


    Waiting for rescue after the alarm


    Elevator maintenance personnel reminded the public that when trapped in a small space inside the elevator, there is no need to worry, the elevator is not sealed, the top is provided with a vent, and the hall door has a gap. Under normal circumstances, it will not cause the trapped person to suffocate. dead. Therefore, trapped personnel should not panic, to maintain peace of mind, press the emergency electric bell alarm in the elevator in time, and wait patiently for the rescue after the alarm, do not take the tricks, climb out of the car and other self-help behaviors, blindly Self-help will cause unnecessary personal injury or death.

The effect of summer machine room temperature on the normal operation of the elevator

    1 Reasons for the temperature rise in the equipment room


    1.1 The location of the building structure of the machine room itself


    Most of the elevator rooms are on the top floor of the building. Some of the machine rooms are a raised room on the roof of the building. The roof and four walls of the machine room are all external structures. The external protective structure is also the external wall that we all say, and its temperature is closely related to the greenhouse temperature, thus affecting the indoor temperature.


    In the hot weather in summer, the outdoor temperature is high, and the temperature of the external protection structure is also high, which leads to an increase in the indoor temperature of the machine room. For a room, the proportion of the outer guard structure occupying the entire maintenance structure is larger, and the indoor temperature is more affected by the outdoor temperature. Therefore, the position of the machine room determines that the machine room is affected by the ambient temperature and the sun exposure during the summer. room.


    1.2 Heat emitted by the electrical system


    The main heating components of the electrical system of the equipment room include inverters, braking resistors and electric motors. Among them, the inverter and the motor consume a part of the electric energy and release it in the form of heat due to its own efficiency. The braking resistor is used to dissipate the electric energy generated by the elevator regenerative power and release it in the form of heat. Both of these heats are dissipated into the machine room, causing an increase in room temperature.

    (1) Inverter


    The frequency converter consists of a main circuit and a control circuit. The main circuit is a power exchange part that supplies a voltage-regulating and frequency-modulated power supply to the motor, and is composed of a rectifier, a smoothing circuit and an inverter. Among them, the inverter component insulated gate bipolar transistor (IGBT) in the inverter is the main heat source of the inverter. The heat generated by the IGBT is mainly concentrated at the moment of opening and closing. Therefore, when the switching frequency is high, the heat generated by the inverter becomes large. The frequency converter for the elevator needs to be started frequently, thus releasing a large amount of heat.


    (2) Braking resistor


    The braking resistor itself is the energy consumed to be converted into heat. For example, when the elevator is idling up, the counterweight is heavier than the car, the main rotor is rotating, and the magnetic flux of the stator coil is cut to generate self-generation, so that the motor changes from the electric state to the power generation state. This regenerative energy is passed through the braking unit of the frequency converter and is eventually consumed by the braking resistor in thermal energy. In the work, there was a unit that did a test. Two elevators of the same frequency were used. One of the elevators used external power as the power, the elevator regenerative power was consumed by the braking resistor, and the other elevator used external power and power saving. The feedback device is powered, and the energy of the power-saving feedback device comes from the regenerative power generation of the elevator. After a period of operation, the external power consumption is 35% less than the other power consumption. It can be seen how much heat is generated by the braking resistor, which is about 1/3 of the elevator's power consumption.


    (3) Motor


    The motor itself has a certain amount of power consumption. According to the motor's heat formula Q=I2Rt, the heat released during motor operation is proportional to the square of the current. The electric motor has the largest current during the starting and braking process, and the elevator, as a vertical transportation vehicle, frequently starts and brakes, and generates a large amount of heat.


    2. The effect of high temperature in the machine room on the normal operation of the elevator


    2.1 Impact on electrical control systems


    (1) High temperature is easy to cause abnormality of the microcomputer control board program


    The electronic device on the microcomputer control board or PLC is logically controlled by voltage and current comparison, and responds to external commands. Due to the material temperature characteristics of the electronic device, the logic judgment of the electronic device is higher than the allowable temperature, the control panel of the microcomputer is unstable, the elevator is prone to failure, and the normal operation is affected (for example, the elevator is suddenly stopped during normal operation of the elevator, and the elevator is operated. When the door is not opened or closed, the elevator can not be changed to speed in the door area, and it is not easy to find the fault point at the same time.


    (2) High temperature and easy damage to electronic components


    (a) Inverter


     The failure rate of the inverter increases exponentially with the increase of temperature, and the service life decreases exponentially with the increase of temperature. The ambient temperature rises by 10 °C, and the service life of the inverter is halved.


     When the ambient temperature exceeds the allowable temperature, the parameter turn-on time and turn-off time of the inverter device in the inverter inverter circuit will change, resulting in one device being turned on during the alternation process, and the other device will be turned off in the future. Broken, causing "straight through" between the upper and lower devices of the same bridge arm, so that the part is in an instantaneous short-circuit state, the inverter is instantly damaged immediately, and the inverter cannot work normally. At the same time, the insulation performance of the inverter will be greatly reduced, which will easily cause damage to the inverter and cause elevator failure.


    (b) Braking resistor


    When the ambient temperature is too high, it is easy to make the braking resistor heat dissipation time too long. If the elevator runs frequently, the heat of the braking resistor accumulates many times, eventually causing the braking resistor temperature to be too high and damaged, and even causing a fire and other safety accidents.


    (c) Other electronic components


    When electronic components such as contactors, relays, and transformers operate, resistance loss occurs due to current passing through the conductor and the coil; in the AC circuit, eddy current and hysteresis loss are generated in the magnet due to the action of alternating electromagnetic. Almost all of these losses are converted into heat, some of which is lost to the surrounding medium, and some of which are trapped in the appliance, causing the temperature of the appliance to rise. At this time, if the ambient temperature is too high, the heat dissipation of each electronic component is poor. First, the reliability of the electronic component is greatly reduced; second, the service life of the electronic component is reduced, and even the electronic component is damaged. Statistics show that for every 2 °C increase in temperature of electronic components, the reliability is reduced by 10%. When the temperature rises by 50 °C, the lifetime is only 25 °C.


    When the ambient temperature exceeds the allowable temperature of the equipment room, it will seriously affect the heat dissipation of the traction motor. Due to the frequent start and brake of the motor, the motor itself will release a large amount of heat, and the high temperature of the equipment room cannot be eliminated in time. The motor continues to be in a high temperature environment. Running, it is easy to burn the coil and damage the motor.


    2.2 Impact on mechanical systems


    The mechanical system of the elevator machine room is mainly a traction machine. The traction machine is usually composed of an electric motor, a brake, a reduction gear box, a traction sheave, a guide wheel, a frame, a wheel hand wheel and the like.


    (1) Influence on traction motor


    When the ambient temperature exceeds the allowable temperature of the equipment room, it will seriously affect the heat dissipation of the traction motor. Due to the frequent start and brake of the motor, the motor itself will release a large amount of heat, and the high temperature of the equipment room cannot be eliminated in time. The motor continues to be in a high temperature environment. Running, it is easy to burn the coil and damage the motor. Although the structural design of the motor has been carefully considered in strengthening the heat dissipation of the stator core. For example, some products are designed to support the end cover, eliminating the traditional base, making the iron core an open structure, enhancing the cooling effect; strengthening the arrangement of the circumferential air passages of the stator and rotor core; increasing the ventilation design of the windshield hole, etc. However, the motor of this structure is used less. Most of the attached cooling fans are controlled by a thermal switch located on the surface of the stator core. When the surface temperature of the iron core reaches about 60 °C, the thermal switch operates, and the fan is turned on to forcibly ventilate and cool the traction motor. When the forced cooling is high in the machine room, the cooling effect is not obvious. Considering that forced cooling fails to cool down, the motor temperature will continue to rise. Some motor products have a thermistor embedded in each phase winding. When the motor temperature rises to 155 °C, the internal thermistor resistance increases sharply, and the external circuit thermal protection relay operates. The control circuit forces the elevator to stop at the nearest station and stops the door until the motor is cooled. Start running. Although this method can protect the motor, the high temperature weather in the summer is long, and the parking protection is frequently seen, which seriously affects the normal operation and use of the elevator.


    (2) Impact on the gearbox


    The gearbox is composed of a worm gear and a worm. The worm is generally made of a material with high hardness and rigidity. At present, most of the nickel-chromium alloy steel or silicon-manganese alloy steel is used, and it is also forged with carbon steel with a carbon content of 0.4%-0.55%. The surface of the worm must be hardened by quenching or carburizing. The worm wheel rim is machined by a low friction coefficient phosphor bronze, tin bronze or copper tin nickel alloy. Since the thermal expansion coefficients of various materials are different, and the thermal expansion coefficient of the worm wheel is about 1/2 of the thermal expansion coefficient of the worm, when the temperature in the machine room is higher than 40 ° C, the heat in the air and the heat generated by the rotation and friction of various components in the reduction gear box When the two are added together, the temperature inside the gearbox will be higher, and the continuous high temperature will cause thermal expansion of the components, thereby destroying the manufacturing precision of the worm gear in the reduction gearbox, and reducing the axial clearance of the turbine shaft and the worm shaft. Small, the meshing surface is increased, the frictional friction of the friction surface is increased, the wear is accelerated, and the comfort of the elevator operation is seriously affected. At the same time, abnormal noise is generated and the worm gear is damaged (for example, the elevator machine room is heard when riding the elevator) There is a rumbling sound, there will be abnormal vibrations in the car, etc.). At the same time, the continuous high temperature in the gearbox will also reduce the viscosity of the lubricating oil, which is not conducive to the formation of the lubricating oil film, and will accelerate the oxidation of the lubricating oil, affecting the lubrication effect of the worm gear and worm, and increase the wear of the worm gear.


    3 How to control the temperature of the equipment room


    3.1 Building structure


    The elevator machine room is used for maintenance structure insulation treatment to reduce the influence of outdoor temperature on indoor equipment in high temperature weather in summer. At the same time, it is not allowed to neglect the insulation of the maintenance structure and reduce the thickness of the maintenance structure because it is the equipment room.


    3.2 Installation of ventilation and cooling equipment


    In the natural ventilation state, install ventilation equipment to meet the temperature requirements of the equipment room, and install air conditioners. When installing ventilation equipment (such as exhaust fans), it should correspond to the ventilation openings of the equipment room (such as blinds), so that the air will convect, thus improving the temperature of the equipment room.


    3.4 The use unit and maintenance unit should arrange full-time personnel to strengthen management


    The maintenance unit should regularly check whether the cooling equipment is working properly, and regularly check the operation of the heat source (such as inverter, braking resistor, motor). For units with multiple elevators, in the hot weather in summer, they should be alternately operated to avoid using only one elevator for convenient ride or other reasons, increasing the running load of the elevator in hot weather. In addition, the use unit should be equipped with fire extinguishers for each elevator room.


    4 Conclusion


    The continuous improvement of the intelligent degree of the elevator control system can not completely eliminate the elevator failure, and the trend of frequent failures of the elevators in use will not change. However, through the discussion and analysis of the building structure, electrical control system and mechanical system of the elevator engine room, the targeted measures are taken to effectively control the various links, which can ensure that the temperature of the elevator room in the summer high temperature weather is within the normal range, and finally eliminate or Reduce various faults caused by high temperature, ensure the elevator operates in a safe, stable and reliable environment, and better serve the users.

This article tags: elevator elevator knowledge elevator cooling elevator high temperature

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