Braking resistors turn your kinetic energy into panel heat. Regeneration sells it back to the grid. Between those two sentences sits an investment decision that deserves numbers, not slogans.
The energy math
Estimate the energy per braking event (½Jω² for rotating masses, mgh terms for lowering), multiply by events per hour and operating hours per year. A slitting-line winder braking coils several times an hour dissipates real megawatt-hours annually; a conveyor stopping twice a day does not. Then compare:
- Resistor path: cheap hardware, energy burned, plus a subtle second cost — the heat lands in your panel room and sometimes in your air conditioning bill.
- Regenerative path: smarter infeed hardware (S120 SLM/ALM, or regenerative/AFE variants in other families), energy returned, and with an ALM the bonus of clean, controlled DC bus and low-harmonic input current.
Our worked rule of thumb from retrofits: cyclic braking above roughly 10–20 kW average dissipation, on a machine running two-plus shifts, usually pays back regeneration hardware within a small number of years at current energy prices — the 650 mm slitting line we rebuilt around a regenerative S120 infeed is documented in our projects.
Non-energy deciders
Generator-fed systems (ships!) often cannot burn braking energy freely nor tolerate dirty rectifiers — regeneration or active infeeds win on power quality alone. Conversely, safety-related stopping sometimes still wants a resistor as the always-available sink independent of grid state.
FAQ
Can regeneration and a resistor coexist? Yes, and on critical machines it is good design: regen for economy, chopper+resistor as the fallback sink.
Does regen stress the motor differently? No — the motor does not care where the energy goes; the infeed does.
Zone Otomasyon calculates the payback per machine before recommending either path. Get the numbers.