Application of Sunwoele VFD (Variable-frequency Drive) on escalators

I. Overview:?

The escalator is a kind of people-carrying lifting equipment commonly used in shopping malls, stations, and airports. There are two automatic escalators in a shopping mall, which are driven by 11kW (four-pole) AC motors, and the escalators are driven to run after being decelerated by a gearbox. One of the two escalators is used as the uplink, and the other is used as the downlink. After running for a period of time, they are switched artificially, that is, the uplink switch is downlink, and the downlink switch is uplink operation. 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 escalator controlled by speed control can only idle at the rated speed, which is very 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 trouble to normal use. Therefore, the escalator is modified by frequency conversion and speed regulation, and the speed is reduced when no one is riding, and then smoothly accelerated to the rated speed when someone is riding. 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.

2. Renovation plan

Use two Sunwoele HSF600 general-purpose VFD (Variable-frequency Drive) to control 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 operating 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 tilted slightly downward. Since the running 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.

2 Elevator deceleration when no one is on board

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 50Hz. For safety considerations, the acceleration must be completed before people step on the escalator. The acceleration time is t2. The time from stepping on to stepping off the escalator is t1. When someone walks into the entrance, the sensor signal is sent to the timer, the normally open contact of the timer is closed, the VFD (Variable-frequency Drive) starts to accelerate to the normal speed, and the timer starts counting at (t0+t1+t2) Someone walks into the entrance within seconds, the signal input by the sensor resets the timer and restarts timing, and the escalator keeps running at normal speed. Within (t0+t1+t2) seconds, when no one enters the entrance, after (t0+t1+t2) seconds the VFD (Variable-frequency Drive) will slow down to run at 15Hz, and the escalator will automatically switch to idle running.

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 stop" of the VFD (Variable-frequency Drive), which may cause harm to passengers. Considering that the frequency conversion of the two escalators is installed in the same control room, and the escalator running upward is always Electric work. So the DC bus of two VFDs (Variable-frequency Drive) is connected through the AC contactor to form a DC bus, and the regenerative energy generated by the down escalator is sent to the DC bus and all used by the up escalator, without energy waste. But Considering that sometimes an escalator may be used for downward running alone, energy consumption braking is used to deal with regenerative energy. Sunwoele VFD (Variable-frequency Drive) has a built-in braking unit, which only needs to be connected to the +?B terminal. Just plug in a 50Ω, 1kW braking resistor.

4 Electromagnetic brake

When an emergency stop occurs for some reason, it is not necessary 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. .

3. Functions after modification

1 The "long-term operation mode" of the original elevator and the "automatic passenger-carrying operation mode" coexist, and the user can choose to use one of the modes at any time. When the "long-term operation mode" of the original elevator is selected, the VFD (Variable-frequency Drive) The control circuit is completely withdrawn. This allows users to switch easily when they need to select the original mode or when the VFD (Variable-frequency Drive) control circuit needs maintenance, ensuring the normal operation of the elevator.

2 After the line is reconstructed, it is guaranteed that it can meet the requirements of China's national GB-16899 safety standard for escalators in any working mode.

3 "When the automatic passenger-carrying operation mode is running, the start, stop or speed change is smooth and smooth, without jumping feeling, and the comfort is good.

4 Extend the service life of the equipment and reduce the self-loss of materials. Such as: motor life, chain loss, belt wear and so on.

5 When there are no passengers, the elevator runs at low speed, and when a passenger arrives at the entrance, the elevator automatically turns to full speed. If there are no more passengers after passengers leave the elevator, the elevator will automatically return to idle running after a delay.