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Escalator energy-saving renovation

Jan 28, 2019

1 original circuit technology defects


    Escalators are typical equipment for transporting passengers in public places, and have been widely used in shopping malls, airports, terminals, subways, hotels and other places. However, due to technical and financial reasons, the conventional escalators in China are mostly powered by power supply. The direct startup mode is started every day when it starts to operate, and runs at a constant speed until it is off duty or until the specified time. The usage rate is generally low. To sum up, the ordinary escalator has the following defects.


    (1) Large energy consumption: Due to the direct start mode, ordinary escalators generally run more than 10 hours a day, regardless of the presence or absence of passengers, always maintain high speed operation, and consume a lot of power, especially in some subways, airports, medium and large shopping malls. The periodicity is obvious.


    (2) Large mechanical wear and short service life: due to running at a constant speed for more than 10 hours per day, the elevator components are subject to unnecessary wear and fatigue damage, such as handrails, comb plates, steps, chains, motors, and deceleration. Parts such as boxes are worn out. Generally, the life of such escalators is about 10 years. After this period of time, the main components are worn very seriously and need to be replaced with new ones.


    (3) The failure rate is high, resulting in high use cost: since the ordinary escalator always maintains high-speed operation, a large number of wearing parts are frequently replaced, which requires a large amount of cost; increased wear and high heat generation also lead to escalator failure rate. The increase will further increase the user's use cost and also increase the maintenance amount of the escalator and affect normal use.


    2 Transformation requirements


    This unreasonable and uneconomical operation mode is inconsistent with the state's policy of promoting energy conservation and consumption reduction and improving the operational efficiency of equipment. This makes us find ways to solve the above-mentioned defects and achieve the goal of saving costs and improving economic efficiency. However, the escalator belongs to special equipment, and it also meets the national mandatory standards while achieving energy-saving and economic benefits. Therefore, the modified system must meet: (1) Start-up operation is stable and there is no jitter. (2) When no one is riding the ladder, ensure that the escalator automatically and smoothly transition to energy-saving operation. (3) It shall be possible to indicate to the passenger whether the escalator is available for use and its direction of operation. (4) The escalator that is automatically activated should be automatically stopped after a sufficient period of time (at least 10 s for the expected passenger delivery time). (5) If the user enters from the direction opposite to the predetermined running direction, the escalator shall start in the predetermined direction for not less than 10 s. (6) The operation should be started before the user walks to the intersection of the comb teeth. (7) When using the service control device, all other start switches should not function, that is, when more than one service control device is connected, it does not work, or it needs to be activated at the same time. The safety switch and safety circuit should still function.


    3 Ways to save energy


    With the advancement of science and technology and the continuous introduction of many foreign advanced technologies, the way of energy saving for escalators has evolved to the following four types.


    (1) Automatic control operation mode: Install photoelectric sensor on the upper and lower mouth of the escalator. Once the sensor detects that passengers enter the escalator (about 13 m from the comb plate), the escalator starts to run. If the passenger continues to enter the escalator, the escalator will always The rated speed is operating normally. If no passengers are detected in the preset time and the passenger exits the escalator or the exit side sensor detects that the last passenger has left the escalator, and no passengers are detected to enter the escalator within the preset time, the escalator will automatically Stop the ladder. When the passenger enters the escalator, the escalator is put into operation.


    (2) Y-△ operation mode (ECO mode): After the escalator is put into operation by the escalator Y-△ starting device, when the escalator is at no load or light load, the control system automatically switches the drive motor from the △-type operation to the Y-type Run to save energy. When the escalator load increases, the escalator automatically turns into a △ type operation.


    (3) Method of soft start of the motor: The principle of photoelectric induction is also used to soft start the motor.


    (4) Frequency conversion operation mode: Add frequency conversion device on the escalator, and automatically adjust the running speed of the escalator according to the passenger flow situation. When the escalator has no passengers, the escalator runs at a low speed; when the escalator photoelectric switch detects that there are passengers, the escalator starts to accelerate and reaches the rated running speed: when the system does not detect the passenger within a certain period of time, the system starts to decelerate and stays at low speed. State until there is a passenger demand again.


    We can compare several energy-saving operation modes according to the requirements that the system must meet: 1 Automatic control operation mode Energy-saving effect The obvious control method is simple and reliable, and the required cost is low; the disadvantage is: first, it will cause the escalator to start and stop frequently; Second, the elevator stops running after unmanned induction. The passenger does not know whether the elevator can ride and the direction of the elevator operation, and does not meet the national mandatory standards. 2Y-△ operation mode has energy-saving effect (in theory, it can save about 30%), but after the escalator starts, it has been running continuously at rated speed, increasing the consumption of the escalator: there are some problems in the escalator detection of heavy load and light load. When the escalator is lightly loaded, the system may still run at a slow speed, and the basic functions of the escalator will be affected. 3 Using the soft start of the motor, in addition to the failure to identify the direction of the defect, the interference to the power grid is also very large. 4 frequency conversion operation mode has outstanding power saving effect (in theory, it can save about 60% of electricity). Compared with the automatic operation mode, there is no frequent starting problem, the escalator wears little, and the crawling speed can prompt the passenger to take the ladder direction.


    4 transformation plan


    The frequency converter has been widely used in production and life in China. The medium and high performance vector frequency converter can provide sufficient output torque and strong overload capability. The speed adjustment accuracy is high. The speed error can reach <0.5% during open loop, and the torque response can be achieved. Short time <10 ms: With super overload capability, it can ensure safe and powerful operation under heavy load. After several years of work practice, the energy-saving renovation project of ordinary escalators with inverter as the core has quietly emerged. The specific plan is:


    (1) Main configuration: 1 vector inverter for elevator; 7PLC (microcomputer control device); 3 contactor, relay; 4 photoelectric sensor.


    (2) Control principle: Based on the original power frequency control system, the control system is equipped with a new additional control cabinet composed of inverter, photoelectric switch, special controller for escalator frequency conversion operation and other necessary auxiliary components. When the escalator starts running, it is started by the inverter. When the escalator reaches the rated speed, if there is no passenger to take the ladder, the escalator will automatically drop from the rated speed to 20% of the rated speed. If the sensor installed at the entrance and exit of the escalator detects that there is a passenger riding the ladder, the speed of the escalator will rise smoothly to the rated speed. If the passenger continues to enter the escalator, the escalator will continue to operate at the rated speed. If the sensor at the entrance of the escalator does not detect that a passenger has entered the escalator within a predetermined time, the escalator will automatically go to the crawling speed.


    (3) Working characteristics: 1 The frequency conversion speed regulation energy-saving control device coexists with the original system dual system, borrowing the safety conditions of the original system and the safety conditions of the two systems are logical “and” relationship. 2 The control cabinet is designed as a movable structure. Put the control cabinet into the equipment room during normal operation; remove the control cabinet out of the equipment room during maintenance. The design has taken into account heat dissipation, movement and grounding issues. 3 The variable frequency speed control energy-saving control device adopts the signal of the original system and adopts the relay sampling method. 4 The installation position of the photoelectric signal sensor should be as close as possible to the outside of the escalator entrance. Consider not processing the mechanical part of the escalator as much as possible. The sensor installation should pay attention to protection and a reasonable wiring process to ensure the reliability of operation. 5 Operation status: When the elevator is not used, the escalator runs at 20% of the rated speed, and the system is in a state of energy saving; when the ladder is taken, the escalator automatically transitions to the rated speed at the energy-saving speed; the system is operated at 50% of the rated speed during maintenance. 6 Implementing national standards, the improvement of the original escalator system and national standards must be improved.


    5 Advantages after the transformation


    Advantages of frequency conversion energy-saving retrofit of escalator


    (1) The system adopts the control combination of PLC programmable controller and inverter, which has strong function and small workload.


    (2) Energy-saving is obvious: when no one is riding the ladder, the escalator is automatically and smoothly transitioned to energy-saving operation, and runs at 20% of rated speed. At this time, the actual operating power of the motor is only about 40% of the original, and the power consumption is significantly reduced.


    (3) Reducing wear and tear: 80% of the escalator is a mechanical system. When the mechanical system runs at a high speed for a long time and runs at a slow speed, the degree of wear is different. Reduced wear of mechanical components due to reduced speed

This article tags: escalator photoelectric microwave photoelectric sensor