Calculate braking energy, peak power, and resistor range. Compare cycle loading drive limits and margins. Plan reliable deceleration for repeated machine stops with confidence.
| Item | Value | Unit |
|---|---|---|
| Brake chopper clamp voltage | 700 | V |
| Drive minimum safe resistance | 20 | Ohm |
| Total reflected inertia | 2.4 | kg.m^2 |
| Start speed | 1450 | rpm |
| End speed | 100 | rpm |
| Deceleration time | 4 | s |
| Cycle time | 30 | s |
| Safety factor | 1.25 | ratio |
| Calculated kinetic energy removed | 27.52 | kJ |
| Calculated peak braking power | 6.88 | kW |
| Calculated average power | 0.92 | kW |
| Calculated maximum usable resistance | 71.23 | Ohm |
Angular speed: omega = 2 x pi x rpm / 60
Braking energy removed: E = 0.5 x J x (omegastart2 - omegaend2)
Peak braking power: Ppeak = E / deceleration time
Cycle average power: Pavg = E / cycle time
Maximum usable resistance: Rmax = Vbrake2 / Ppeak
Duty cycle: duty = deceleration time / cycle time x 100
Recommended continuous power: Pcontinuous = Pavg x safety factor
The selected resistor must stay at or above the drive minimum safe resistance. It must also stay at or below the maximum usable resistance.
A VFD braking resistor calculator helps estimate stopping energy before hardware is selected. It turns motion data into resistor sizing guidance. That reduces guesswork during drive design, retrofit work, and maintenance planning. Faster checks can also prevent nuisance overvoltage trips during hard deceleration.
During deceleration, a motor can act like a generator. The returning energy raises the DC bus voltage. A braking resistor converts that excess energy into heat. The correct resistor value and power rating help the drive stop loads safely. Correct sizing also supports repeat cycles, stable braking, and better equipment uptime.
This calculator uses brake chopper voltage, minimum safe drive resistance, total reflected inertia, start speed, end speed, deceleration time, cycle time, and safety factor. These values describe how much kinetic energy must be removed. They also show how often that energy returns. The result is a practical view of peak demand and average thermal loading.
Kinetic energy shows the amount removed from the rotating system. Peak braking power shows the short burst seen during deceleration. Cycle average power shows thermal demand over the full cycle. Maximum usable resistance shows the highest resistor value that can still absorb the required peak energy. If the drive minimum resistance is higher than that limit, the design is not feasible without changing the stopping method.
Many people size only by motor kilowatts. That can miss high inertia loads. A light motor can still need strong braking when the driven mass is large. Another mistake is ignoring cycle time. Repeated stops can overheat a resistor even when single stop power looks acceptable. Safety factor also matters because real machines rarely behave like clean lab examples.
This tool is useful for early sizing and comparison work. It helps teams review braking energy, duty cycle, resistor range, and continuous power needs. It does not replace the drive manual. Always verify resistor compatibility, braking transistor limits, enclosure ventilation, and pulse rating before purchase. Check ambient conditions and mounting method during final selection. That final check protects the drive, resistor bank, and driven machine.
It absorbs regenerated energy during deceleration. The resistor converts that energy into heat. This helps prevent DC bus overvoltage and supports faster stopping.
Resistance controls braking current and power absorption. Too much resistance may not absorb enough power. Too little resistance may violate the drive minimum safe limit.
Cycle time affects thermal loading. A resistor may survive one strong stop but still overheat during repeated stops if average power stays too high.
No. Inertia, speed change, stop time, and repeat rate strongly affect braking energy. Motor kilowatts alone can miss the real braking demand.
The drive minimum safe resistance is higher than the power-based maximum usable resistance. You may need a longer deceleration time, lower inertia, or another braking approach.
Peak power is the short burst during one braking event. Continuous power reflects average heating over the cycle and helps with thermal resistor selection.
Yes. Braking from full speed to zero removes more energy than slowing to an intermediate speed. The energy change depends on both start and end speed.
No. Use it for screening and comparison. Final selection still needs the drive manual, resistor datasheet, duty data, and installation limits.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.