1 Overview Elevators are becoming increasingly common. In surveys of electricity consumption in hotels, office buildings, etc., elevator electricity consumption accounts for 17% to 25% of total electricity consumption, second only to air conditioning electricity consumption, and higher than lighting, water supply, etc. Currently, elevators abroad are divided into two types: "energy-consuming type" and advanced "feedback type". When purchasing new elevators, the proportion of customers choosing "feedback type" elevators is increasing. The energy-saving effect is related to the elevator power, the entire elevator system, the elevator balance system, etc. The following situations have better energy-saving effects: (1) The higher the floor of the elevator, the more frequent the braking, and the more energy is saved; (2) The newer the elevator is installed and used, the greater the mechanical inertia, and the more energy is saved; (3) The faster the elevator is, the more frequent the braking, and the more energy is saved; (4) The more frequently the elevator is used, the more frequent the braking, and the more energy is saved. Adopting advanced power electronics technology, the quality is reliable and safe, and the fully intelligent operation is so simple that no operation is required from the customer. There is also a complete after-sales warranty service to solve all the worries of customers. One-year warranty, lifetime maintenance. 2. Overview of Product Principles With the continuous expansion of modern production scale and the continuous improvement of people's living standards, the contradiction between power supply and demand is becoming increasingly prominent, and the call for energy conservation is growing louder. Relevant statistics show that the power consumption of motor-driven loads accounts for more than 70% of the total power consumption. Therefore, energy conservation in motor-driven systems has particularly important social significance and economic benefits. There are two main ways to save power in motor-driven systems: (1) Improve the operating efficiency of motor-driven systems. For example, speed regulation of fans and water pumps is an energy-saving measure aimed at improving the operating efficiency of the load. Another example is that the use of frequency converter speed regulation to replace asynchronous motor voltage regulation speed regulation in elevator traction machines is an energy-saving measure aimed at improving the operating efficiency of the motor. (2) Convert the mechanical energy (potential energy, kinetic energy) on the moving load into electrical energy (regenerated electrical energy) through an energy feedback device and send it back to the AC power grid for use by other nearby electrical equipment. This reduces the power consumption of the motor-driven system per unit time, thereby achieving the purpose of energy conservation. 3. Taking a lifting elevator as an example, the second type of energy-saving principle is introduced. Elevators using variable frequency speed control (VFDs) reach their maximum operating speed upon startup, maximizing their mechanical function. Before reaching the target floor, the elevator gradually decelerates until it stops. This process involves the traction machine releasing its mechanical energy. Furthermore, the lifting elevator is also a potential energy load. To evenly distribute the load, the load driven by the traction machine consists of the passenger car and the counterweight. Only when the car's load is approximately 50% (about 7 passengers in a 1-ton passenger elevator) are the car and counterweight balanced. Otherwise, there will be a mass difference between the car and the counterweight, generating mechanical potential energy during elevator operation. Excess mechanical energy (including potential and kinetic energy) during elevator operation is converted into DC electrical energy by the motor and VFD and stored in the capacitor in the VFD's DC circuit. The capacitor acts like a small reservoir; the more electrical energy returned to the capacitor, the higher the capacitor voltage (like a reservoir with excessively high water levels). If the stored energy is not released in time, an overvoltage fault will occur, causing the VFD to stop working and the elevator to malfunction. Currently, most variable frequency speed control elevators in China use resistors to dissipate the energy stored in capacitors to prevent capacitor overvoltage. However, resistor energy dissipation not only reduces system efficiency, but the large amount of heat generated by the resistors also deteriorates the environment around the elevator control cabinet. The function of an energy feedback device is to effectively feed the energy stored in the capacitor back to the AC power grid for use by other surrounding electrical equipment, resulting in significant energy savings, typically ranging from 21% to 46%. Furthermore, since there are no resistive heating elements, the machine room temperature decreases, saving on air conditioning power consumption. In many cases, saving on air conditioning power consumption often leads to even greater energy savings. A key feature of the new energy feedback device compared to other energy feedback devices currently available domestically and internationally is its voltage adaptive control feedback function. Generally, energy feedback devices determine whether to feed back energy based on the DC circuit voltage UPN of the frequency converter, using a fixed feedback voltage UHK. Due to fluctuations in the grid voltage, if the UHK value is too small, false feedback will occur when the grid voltage is too high; if the UHK value is too large, the feedback effect will significantly decrease (the energy stored in the capacitor is prematurely consumed by the resistor). The new energy feedback unit employs voltage adaptive control. Regardless of grid voltage fluctuations, it only feeds the stored energy back to the grid when the elevator's mechanical energy is converted into electrical energy and fed into the DC circuit capacitor, effectively solving the shortcomings of traditional energy feedback systems. Furthermore, the new energy feedback unit boasts comprehensive protection and expansion capabilities, making it suitable for both retrofitting existing elevators and integrating with new elevator control cabinets. Using the new energy feedback unit to power the new elevator control cabinet not only significantly saves energy but also effectively improves the quality of the input current, achieving higher potential compatibility standards. The new energy feedback unit is compatible with a wide range of voltage levels, including 220VAC, 380VAC, 480VAC, and 660VAC. The product lifespan, according to testing, exceeds 70,000 hours of reliable operation. This means that even if the elevator operates 24 hours a day, 365 days a year, the energy feedback unit can be used continuously for 8-10 years or more. Unlike a light bulb, which operates continuously for extended periods, an elevator has a waiting or standby state. The feedback unit may only operate for 10 hours a day, which is already considered a significant usage. Based on this calculation, the lifespan of a feedback device is longer than that of an elevator. Furthermore, many mechanical components in an elevator have limited lifespans. Therefore, in terms of lifespan, a feedback device significantly outlasts an elevator.