Braking Resistor Sizing Calculator
Sizing a braking resistor wrong means tripped drives, scorched cabinets or wasted budget. This calculator gives you a first-order estimate using the same equations every drive manufacturer publishes — peak power, R_max from the DC bus voltage, average dissipation across the duty cycle, and energy per braking pulse.
Inputs
Calculated values
- Peak braking power
- 13,500 W
- Maximum resistance R_max
- 45.1 Ω
- Continuous average power
- 675.0 W
- Energy per braking pulse
- 20,250 J
- P_peak = P_motor × η_regen
- R_max = V_bus² / P_peak
- P_avg = P_peak × (t_decel / t_cycle)
- E_pulse = ½ × P_peak × t_decel
This calculator provides preliminary sizing only. Always validate with the drive manufacturer's worksheet and prototype testing.
How to use this calculator
- Enter the motor's rated power in kilowatts — use the nameplate value, not running load.
- Set the regen duty cycle: how often the motor decelerates vs. runs steady-state (e.g. 10–20 % for elevators, 5 % for general industrial).
- Enter deceleration time in seconds and cycle time (the period of one full run-decelerate cycle).
- Set the DC bus voltage — 780 V for a 400 V AC drive at the regen threshold, 380 V for 230 V single-phase.
- Read R_max — pick a standard resistor value at or below this number, never above.
- Verify the chosen resistor's continuous power rating meets the calculated average dissipation with margin.
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Standard samples are provided free of charge in reasonable quantities (shipped within 2–3 business days). Custom samples are delivered within 2–4 weeks. Please use the form on the right to tell us:
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- Target part number or key specs (power / resistance / package)
- Application scenario and estimated annual volume
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