Regenerative Energy
The energy that flows back into the supply when the motor turns into a generator while decelerating or while being driven by the load. When the back-EMF rises above the supply voltage the direction of the current reverses and the voltage of the supply line rises. If there is no element to absorb the energy, the voltage keeps climbing.
It most often appears in three situations: rapid deceleration, lowering movements where the load drags the motor, and moments of direction change. The amount of energy grows with the inertia of the load and with the square of the speed.
The type of source determines the outcome:
- With battery supply: The battery can accept this current and the voltage rises in a measured way. Extra precautions are usually not needed.
- With a switch-mode power supply: The supply cannot sink current, the voltage climbs rapidly and both the supply and the driver may be damaged. This is a common failure in laboratory or panel-fed installations.
Countermeasures: the bus capacitor absorbs short pulses, a braking resistor turns continuous energy into heat, and over-voltage protection shuts the output down when the limit is exceeded. Lengthening the deceleration ramp also lowers the returned power directly and is often the easiest solution. Energy recovery is not stated in the product data for AXI modules; this topic is a general design subject.
Where this term is used: DC Motor Driver Selection Guide