Escalators are widely used in hotels, shopping malls, subways, train stations, office buildings, and airports. It plays an important role in facilitating customers and improving service quality. However, due to the particularity of its use, some escalators are often in light or no-load conditions. This will certainly waste a lot of electricity, and it will also cause the escalator to wear out. According to the current relevant technical standards, the escalator's busy work can be divided into two types: ordinary type and public transport type. The most typical and most common type of public transport escalator is an outbound uplink escalator installed in a subway station. Our field tests on this escalator showed that the duration of the rushing flow of people on the escalator is approximately 45 seconds each time the subway arrives. If calculated on a subway every 3 minutes. The escalator's "duty on load" is only about 25%. In the rest of the time, the escalator is operated under no-load or very low load. Public transport escalators are still the case, let alone the situation of other ordinary escalators. Therefore, it is necessary to take energy-saving measures for escalators.

 

Common energy saving methods and control systems

For escalators, the commonly used energy-saving methods include the “automatic restart” energy saving method, the “△-Y switching” energy saving method, and so on. The former method is to stop the operation of the escalator when no one is riding the ladder, and start the escalator when someone takes the ladder, so as to achieve the purpose of power saving. Since the method of completely blackout is adopted, energy saving is very considerable. Generally can achieve 50% of electrical energy savings. However, this method has some drawbacks. First of all, when no one takes the elevator, the escalator is stopped. Most passengers think that the escalator is stopped or is being repaired and turned to the nearby stairs to go upstairs, especially when the stairs and the escalator are installed in parallel. Even more so, it lost the role of the escalator. The latter method uses the classic star and delta connection to start the conversion. However, there are some disadvantages in the compromise method. Because the star connection method has only 1/3 of the delta connection, the star connection method has a slower speed, and there is a 2 to 3 second conversion time between the two. When the position of the probe is too close to the entrance of the escalator, an impact will be generated due to the conversion of the star and delta connection after the passengers are on the ladder, which will deteriorate the ride comfort of the escalator and even cause accidents; if the photoelectric detector is located at a distance from the escalator If the entrance is too far, passengers can be prevented from having an impact after going up a ladder. However, they are prone to malfunctions. At the same time, if the passenger flow is continuously interrupted and the escalator is frequently started, it will also have adverse effects. There are three kinds of escalator control systems: relay control system, PLC control system and micro-controller system. The escalators currently used in the market are also controlled by relays. Because the relay control system has large noise, inconvenient maintenance, and backward control methods, it has not been adapted to the needs of modern people and is gradually being eliminated by people. Although the micro-controller system has great development in terms of intelligence, due to the long development time of the micro-controller system, difficulty in program modification, and the application of anti-jamming, it has limited its application, and the PLC control system has high reliability and stability. Good performance, convenient maintenance and other significant advantages, development prospects.

 

The basic principle of PLC and inverter control

 As the above methods have various defects, the energy saving control method based on PLC and frequency converter is proposed here. At the same time, adopting PLC as the main controller has the following advantages:

 

(1) High reliability and good stability. The threshold value of the input signal allowed by a general PLC is much larger than that of a typical microcontroller. And with external circuits are optically isolated, anti-interference ability is strong. For example, a typical PLC can withstand spikes with a peak voltage of 1000 V and a pulse width of 1 s, and has a variety of protection functions in case of failure. The escalator can be quickly stopped.

 

(2) simple programming, easy to use. At present, PLC generally adopts a relay-controlled form of "ladder" programming, which is easily accepted by technicians of electrical and automatic control.

 

(3) easy maintenance and overhaul. PLC products have perfect monitoring and diagnostic functions, such as visible working status, communication status, I/O status, and abnormal status. Each control step of the escalator can be represented by a fault code, which can greatly reduce the average repair time of the fault. After some PLCs use intelligent positive modules, they can also separate the external fault diagnosis and detection functions from the CPU, thus improving the external faults. Detection function.

 

In general. The escalator's dead time is often greater than the passenger loading time. PLC controller automatically detects the escalator no-load operation for a certain period of time. An instruction is issued to control the inverter to run at a reduced speed, when a passenger steps on the escalator comb plate. The escalator can automatically sense the arrival of passengers through photoelectric sensors installed at the entrance of the comb-tooth plate and start to accelerate. Here, the main function of the frequency converter is to adjust the escalator speed, start and run smoothly, when no one is in the PLC, the system will automatically enter the creep state after the delay instruction to achieve the purpose of energy saving. The photoelectric switch is installed at the entrance of the escalator. When there is a passenger, the photoelectric switch sends a signal, and the escalator is frequency-controlled to the rated speed. After all the passengers leave the escalator, the escalator enters the low-speed running state after a delay. This saves power, reduces mechanical wear and extends service life.