The purpose of the mechanical energy feedback device is to convert the mechanical energy (bit energy, kinetic energy) on the load in motion into electricity (renewable electricity) through the energy feedback device and return it to the AC grid for use by other electrical equipment nearby, so that the motor drag system consumes electricity from the grid in the unit time, thus achieving the effect of saving electricity.
Take the elevator and the energy feedback device as an example. There are four working conditions when the elevator is running: (1) the empty car is going up and full load is going down, that is, the car or the lighter side of the load is rising, this is the process of releasing the system's potential energy, the tractor is working in the power generation state. (2) the empty car is going down and full load is going up, that is, the car or the lighter side of the load is falling, this is when the system's potential energy is increasing, the tractor is working in the electric state. (3) when the elevator reaches the floor where the deceleration brake is located, the system releases the dynamic energy, the tractor is also working in the power generation state.
When the elevator is running in (1), (3) working conditions, the tractor works in the power-generating state, the generated energy is converted to DC electricity on the DC motherboard by the electric motor and frequency converter. These energies are temporarily stored in the large capacitor of the DC circuit of the frequency converter. The energy feedback system is to convert the DC electricity stored in the large capacitor of the DC side of the elevator to AC and return to the user's grid for use by other electrical equipment nearby.
This is similar to our tap water supply system: we collect the leaked tap water and filter it to meet drinking water standards. Using a pressurized pump, this water is sent to the building’s tap water intake or reservoir and used again. If this water accounts for less than 5% of the entire building’s water use, it will not return to the main tap water pipeline because it is used by other users (the nearest user) before it has had time to return to the main pipeline.
This part of the electricity will not return to the power grid of the power supply, because this part of the electricity is only 20-50% of the electricity used by the elevator, which accounts for less than 5% of the electricity used by the entire building. It will be consumed by other electrical equipment (lighting, computers, air conditioning, refrigerators, etc.).