Regenerative Drives – The Greatest Innovation in Elevator Technology

What are regenerative drives?

    Regenerative drives are undoubtedly one of the greatest innovations in this new generation of elevator technology. The elevators equipped with this technology are highly energy-efficient and reduce the energy consumption up to 70 percent. Mostly, when elevators move upward with a light load and then come downward with a heavy load, the system uses a lot more power than it usually does. In traditional elevators this power is lost as heat, thus substantial amount of energy is wasted over the life the elevators. However, in elevators equipped with regenerative drives, the case is different. These drives capture the generated heat while the elevator is in use and converts it into reusable energy. This energy is transferred back into the system. In this way, a lot of energy is saved and not wasted as heat.

      How do regenerative drives work?

        When power flows into the motor, a lifting torque is created on the shaft and sheave and the elevator cab is lifted. Then, when the can moves downward, the elevator motor acts as generator and transforms the mechanical power into electrical power. The motor basically pumps the current back into the electrical grid where it can be used again by other electrical loads or elevators. This power generated may seem small and negligible in the beginning but over the time these small amounts add up to substantial savings. Regenerative drives help buildings cut down their utility bills. They even reduce the cost and strain of HVAC system by reducing the need of excessive heat in the building.
          Today, most of the elevator companies are manufacturing premium elevators for high-rise buildings that are highly energy efficient. The elevators have improved hardware, control system, and other systems that are not only energy-efficient but also more compact, and even generate power that can be used by the facility. These elevators use software and microprocessor based control system instead of electromechanical relays. Also, they have in-cab sensors that automatically enter sleep mode and turn off light, music and video screens, and ventilation when the elevator is unoccupied. Furthermore, the destination control software in these elevators batches the stop requests which in turn reduces the number of stops and minimizes waiting time.

            What regenerative drives offer?

              There’s a lot that regenerative drives have to offer, including:
                • Substantial Energy Savings Regenerative drives have the capability of recovering and feeding back energy into the electricity grid so that it can be reused by other power-requiring equipment. Everything required for this operation, like LCL line filter and active supply unit are fitted in the drive. It is the work of active supply unit to ensure full power flow in both the modes (motoring and generating). By feeding back the energy to the grid, substantial energy savings are achieved as compared to other traditional braking methods. In case of resistor or mechanical braking, energy dissipates in the form of heat and is wasted. Usually, handling of dissipated heat is an issue when braking power is significant. In such cases additional cooling may be required.
                  • Simplified Installation The installation of regenerative drives is simple as they do not require any external braking devices and the installation footprint is also small. Also, there’s no need to add any cooling to handle the heat generated from resistor or mechanical braking. These drives require less spare parts and their wiring is also simple.
                    • Maximized Efficiency and Performance Regenerative drives reach unity power factor. This power factor basically indicates that the energy is utilized to its full potential. These drives offer a possibility for correction of network power factor in order to counterbalance the low power factors of electrical loads connected to the same network. By doing so, they reduce the requirement for additional power factor correction equipment like large capacitor banks and filters. The active supply unit has the ability to boost the output voltage, which ensures full motor voltage even when supply voltage is low. Regenerative drives also help the building owners to avoid penalty charges that are set by electrical utilities for low power factors. These drives are most suitable for demanding applications. With direct torque control as standard, regenerative drives enable ultra-fast transition between the motoring and generating mode, and in way make it possible to regenerate almost 100 percent of the power continuously.