Elevator emergency feedback device suppliers remind you that with the continuous advancement of technology and the improvement of people's living standards, the requirements for quality of life are also increasing. The use of elevators has become very widespread, and safety and environmental protection have also become the direction of elevator development. Due to the sudden power outage that elevators may encounter during operation, causing people or objects to be trapped inside the elevator, the emergency device for elevator power outage was born.
Structural principle of power outage emergency rescue device
Emergency rescue devices for power outages can be divided into two categories based on their structural principles:
（1） Special emergency rescue device for elevator power outage
It is independent of the elevator control cabinet. When the normal power supply of the elevator loses power, the device takes over all the control of the elevator, controls the car to run to the nearest level position, and opens the door to safely evacuate passengers.
This type of power outage emergency rescue device is generally a complete set of products, installed in a cabinet, with good universality and can be matched with most elevator control cabinets. For elevator production enterprises, as long as the whole set is purchased, installed next to the elevator control cabinet, and the interface wiring with the control cabinet is handled properly, the technical personnel of the elevator production enterprise do not need to spend too much effort to deeply understand the internal structure of the device. Moreover, most power outage emergency device production enterprises provide installation and commissioning services. Therefore, this type of product is very popular among small and medium-sized elevator production enterprises and engineering enterprises, and has been used earliest and most widely in China. This emergency rescue device for power outages consists of two parts: a control circuit and a battery. The control circuit generally consists of a detection and control circuit, a charging circuit, and an inverter circuit. The detection control circuit is responsible for detecting the power supply of the elevator, activating the power outage emergency device in case of power failure, and then detecting the relevant signals of the elevator. When the elevator safety circuit is detected to be connected (if there is a phase sequence relay, it should be short circuited), and the elevator maintenance/normal switch is in normal state, the device starts working to further detect the position of the car. If the car is in the level position, the power outage emergency rescue device provides the power and signal to open the door, and the elevator opens the door for passengers to evacuate; If the elevator car is not in the level position, the inverter circuit is activated to reverse the DC power of the battery into low-voltage low-frequency AC power for the traction motor to operate. The elevator crawls at low speed to the nearest level position, and then opens the door to evacuate passengers. After a few more seconds of delay when the elevator door opens, the rescue is completed and the rescue device is deactivated.
The main drag circuit and door opening control circuit of the system are shown in the following diagram. QA is the main power switch of the elevator, MD is the traction motor, YC is the output contactor of the frequency converter, YC1 is the emergency output contactor for power outage, and YC and YC1 should be electrically interlocked in control.
A Brief Discussion on Emergency Rescue Devices for Elevator Power Outages
It should be noted that this type of power outage emergency rescue device is open-loop controlled during dragging, and the motor speed is not fed back to the inverter board. For ordinary asynchronous motors, this control is completely feasible, but for synchronous motors, open-loop control is obviously difficult to make the motor operate normally at the set speed. Therefore, this type of power outage emergency rescue device is generally not suitable for synchronous traction machines.
Some manufacturers of power outage emergency rescue devices claim that their products not only have automatic power outage rescue function, but also have fault rescue function. That is, once the elevator fails and stops in the middle of the floor and cannot operate, the power outage emergency rescue device will detect the fault. If it meets the operating conditions for rescue, the control cabinet control power supply will be cut off, and the power outage emergency rescue device will implement rescue operation. For example, when all the control circuits of the elevator meet the operating conditions, but due to a fault in the frequency converter, the elevator stops in the middle of the floor and becomes trapped, the power outage emergency device is put into operation. If this function is indeed needed, it should be used with great caution, strictly controlling the conditions for the power outage emergency device to be put into operation, and preventing accidents that may occur during use.
（2） Power outage emergency rescue device controlled by a universal uninterruptible power supply (UPS)
When the normal power supply of the elevator loses power, the device supplies power to the elevator control cabinet (including the frequency converter), and the elevator is still fully controlled by the control cabinet when powered by the backup power supply, running at maintenance or self rescue speed to the level position.
This is a new type of power outage emergency device that has only been used in China in recent years, but it is still not widely used mainly due to the limitations of the frequency converter function. Currently, not all frequency converters can be controlled in this way. Because the power supply provided by UPS is generally single-phase AC 220V, it is required that the frequency converter can operate the traction machine at low speed when powered by a single-phase 220V power supply.
The structure of this type of power outage emergency rescue device is very simple, consisting of a standard UPS and corresponding control circuits. UPS can be placed inside the control cabinet or independently placed next to the control cabinet. Its control circuit is generally placed inside the control cabinet and integrated with the control cabinet design. The following diagram is a common control circuit diagram, where QA is the main power switch of the elevator, MD is the traction motor, YC is the output contactor of the frequency converter, AC is the three-phase input contactor of the frequency converter, TC1 is the single-phase 220V input contactor of the frequency converter, DC is the power contactor of the control cabinet during normal power supply, and TC2 is the power contactor of the control cabinet during power outage emergency operation. AC and TC1, DC and TC2 should be electrically interlocked in control. The power transformer requires a single-phase 220V voltage input.
A Brief Discussion on Emergency Rescue Devices for Elevator Power Outages
Although some frequency converters do not have single-phase 220V input function, they have DC low-voltage input operation function. For example, Yaskawa G5 and L7 frequency converters can use DC 48V for low-speed operation. With this function, a power outage emergency device similar to UPS can be designed. Its structure includes a low-power charging/inverter and a battery. When the power supply is normal, the charging/inverter charges the battery. When there is a power outage, the battery inverts to produce a 220V power supply for the control cabinet to work. At the same time, the battery supplies power to the DC input terminal of the frequency converter, which drives the motor to run at low speed.
Comparison of Emergency Rescue Devices for Power Outages
Through the analysis of the structural principles of the power outage emergency rescue device above, we can compare its performance and provide reference for the development direction of the industry.
（1） Universality
The first type has good generality on asynchronous machines, but its application on synchronous machines is limited; The second type cannot be applied to all frequency converters and is subject to certain limitations in use. However, for frequency converter manufacturers, as long as there is a market demand, it is relatively simple to add single-phase 220V input or DC low-voltage input operation functions, and no additional costs are required. Therefore, in terms of generality, the second category has greater room for development;
（2） Security
The first type of power outage emergency device operates by directly dragging the elevator. Without strict control, there is a high possibility of danger; The second type of power outage emergency device does not directly control the operation of the elevator, but supplies power to the control cabinet, which controls the elevator. In terms of safety, it is not much different from normal operation, and there is no position signal error when restoring normal power supply. Obviously, the safety performance of the second type of power outage emergency device is better.
（3） Economic viability
In terms of the internal structure of the product, the first type of power outage emergency device is much more complex than the second type. Not only does it have safety detection, contactor output and other circuits in the control part, but it also has a three-phase DC inverter part. Therefore, its direct material cost is much higher than that of the second type of power outage emergency device. Moreover, as a specialized product, its output and production scale are far less than UPS, which is a universal product, and it also increases the cost of its product. In terms of price, the first type of power outage emergency device is twice as expensive as the second type.