Design on escalators based on VFD (Variable-frequency Drive) application

The escalator is a kind of manned lifting equipment commonly used in shopping malls, stations, and airports. In the shopping mall, one of the two escalators is used as an uplink and the other is used as a downlink. After a period of operation, it is artificially exchanged, that is, the exchange of uplink is downlink , the downlink exchange is the application of Sunwoele VFD (Variable-frequency Drive) on the escalator for uplink. During the operation, the flow of customers varies greatly at different time periods. Sometimes there may be no one on the escalator. Due to the randomness of the arrival of customers, it is impossible to stop the escalator when no one is taking it. The speed control escalator can only idle at the rated speed, which is uneconomical and wastes a lot of electric energy. Moreover, the chains and belts are worn out and the maintenance period is short, which brings a lot of troubles to normal use. In this way, the wear of the chain and the belt can be reduced; after the speed is reduced, the output power of the motor is greatly reduced, which brings a certain energy-saving effect. The longer the unmanned ride, the more significant the energy saving effect.

1. Retrofit plan

Sunwoele HSF600 general-purpose vector VFD (Variable-frequency Drive) controls the motor of the escalator. When carrying passengers, the VFD (Variable-frequency Drive) is set to external terminal control, and the speed control is set to multi-stage mode, that is, set the normal operating frequency (50Hz) ﹑Deceleration running frequency (15Hz). During maintenance (crawling), the operating frequency is low, around 25Hz.

1. Sensor

The sensor is an infrared sensor, which is installed at the entrance of the escalator at a height of 2.5m from the ground. The focusing lens is aimed at the direction of the visitor and is slightly inclined downward. Since the operation mode of the up and down escalators needs to be exchanged regularly, an infrared sensor must be installed at the entrance and exit of each escalator. Connect the outputs of these two sensors to the input of the timer in the VFD (Variable-frequency Drive). When the escalator is running, disconnect the signal of the exit sensor.

A sensor that uses the physical properties of infrared rays to measure. Infrared ray, also known as infrared light, has properties such as reflection, refraction, scattering, interference, and absorption. Any substance, as long as it has a certain temperature (above absolute zero), can radiate infrared rays. The infrared sensor is not in direct contact with the measured object during measurement, so there is no friction, and it has the advantages of high sensitivity and fast response.

The infrared sensor includes an optical system, a detection element and a conversion circuit. Optical systems can be divided into two types: transmissive and reflective according to their structure. The detection element can be divided into thermal detection element and photoelectric detection element according to the working principle. Thermistors are the most widely used thermal components. When the thermistor is exposed to infrared radiation, the temperature rises, the resistance changes, and the electrical signal is output through the conversion circuit. Photosensitive elements are commonly used in photoelectric detection elements, usually made of materials such as lead sulfide, lead selenide, indium arsenide, antimony arsenide, mercury cadmium telluride ternary alloy, germanium and silicon doping.

Infrared sensors are often used in non-contact temperature measurement, gas composition analysis and non-destructive flaw detection, and are widely used in medicine, military, space technology and environmental engineering and other fields. For example, infrared sensors can be used to measure the thermal image of the surface temperature of the human body at a long distance, and the abnormal temperature can be found, and the disease can be diagnosed and treated in time; the infrared sensor on the artificial satellite can be used to monitor the earth's clouds, and a wide range of weather forecasts can be realized; Infrared sensors are used to detect, for example, the overheating of an engine running on an aircraft.

2. The slow down operation of the elevator when no one is taking it.

Assume that the sensor detects that someone is walking towards the escalator. Generally, the monitoring distance of the sensor is 6m, and the ground distance is about 4.2m. It takes about t0=5s for a person to walk this distance. The 15Hz operation accelerates to 50HzCONTROL. For safety considerations, the acceleration must be completed before people step on the escalator. The acceleration time is 2s. The time from people stepping on to stepping off the escalator is t1. If no one comes within the time period, after t2=5s After a delay, the VFD (Variable-frequency Drive) will slow down to 15Hz.

Sunwoele HSF600 series VFD (Variable-frequency Drive) is a vector-controlled high-performance VFD (Variable-frequency Drive), which is very suitable for constant torque potential energy loads similar to elevators. In addition, it does not need to use PLC, but uses VFD ( Variable-frequency Drive) built-in timing unit, set the timing time of the timing unit to (t0+t1+t2), when someone walks into the entrance, the sensor signal is sent to the timer, and the timer starts timing, at (t0+t1+t2 ) seconds, when no one enters the entrance, the escalator will automatically switch to low-speed operation after (t0+t1+t2) seconds; if someone enters the entrance within (t0+t1+t2) seconds, the signal input by the sensor will Reset and start timing again, and the escalator keeps running at normal speed.

3. Treatment of regenerative energy

When the escalator is running downward, the motor will enter the state of regenerative power generation. The more passengers are carried, the greater the regenerative energy generated. If the regenerative energy is not processed, it will cause frequent "overvoltage" shutdown of the VFD (Variable-frequency Drive), which may cause injury to passengers. However, considering that sometimes an escalator may be used for downward running alone, the energy-consumption braking method is used to deal with the regenerative energy at this time. Sunwoele VFD (Variable-frequency Drive) has a built-in braking unit, just connect the braking resistor to the P and PB terminals.

4. Electromagnetic brake

When an emergency stop occurs for some reason, there is no need to consider restarting as on-load starting (that is, people stand on the escalator to start). For safety reasons, the escalator must have a braking device when it is stationary, and it does not have a braking effect when it is running. .

2. Functions after transformation

1. Keep the "long-term operation" mode of the original elevator and the "automatic passenger-carrying operation" mode coexisting. The user can choose to use one of the modes at any time. frequency Drive) control circuit is completely withdrawn