What is regenerative energy, and do I need a braking resistor?
Regenerative energy is the electrical energy produced back by a motor that is decelerating or being turned by the load. If the energy has nowhere to go, the supply voltage rises. A braking resistor turns that energy into heat and limits the voltage; it is needed in scenarios such as descending a steep slope, lowering heavy loads and frequent direction changes.
What decides whether you need a braking resistor is the amount and frequency of the returning energy. The need is high in the following cases:
- Lifting and platform applications where heavy masses are lowered by gravity.
- Frequent deceleration or direction changes of a high-inertia load.
- Supply from a switch-mode power supply; an SMPS cannot accept reverse current.
The need is low with: small inertia, infrequent stops, battery supply and a long stopping ramp.
Other measures:
- Bus capacitor: Buffers short and infrequent energy pulses; it cannot handle continuous regeneration.
- Lengthening the ramp: Returns the same energy over a longer time, so the peak voltage drops. It is the first thing to try and costs nothing.
- Snubber: Suppresses high-frequency spikes caused by switching; typical RC values are chosen in the 5–20 Ω and 1–22 nF range according to the motor inductance.
Note: regenerative braking or energy recovery is not stated in the product data for the ST42, KS250 and PT500. This is a general power electronics matter; when designing the system it should be evaluated according to the type of supply and the inertia of the load.
The full topic: DC Motor Driver Selection Guide