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BLDC Commutation Timing Calculator
Work out electrical frequency, six-step commutation interval, and a recommended control-loop rate for a trapezoidal (six-step) BLDC motor at a given mechanical speed.
Pole pairs = number of magnet pole pairs on the rotor (a "4-pole-pair" motor has 8 magnet poles). Six commutation steps occur per electrical revolution.
Electrical frequency
200.0 Hz
fe = (RPM / 60) × pole pairs
Commutation interval
833.3 µs
tstep = 1 / (6 × fe)
Hall edges per revolution
24
edges/rev = 6 × pole pairs
Recommended control loop rate
12.0 kHz
floop ≥ margin × 6 × fe
f_e = (RPM / 60) × pole_pairs
t_step = 1 / (6 × f_e)
edges_per_rev = 6 × pole_pairs
f_loop ≥ margin × 6 × f_e
Six discrete commutation states occur per electrical cycle in trapezoidal (six-step) control. The control/current loop should run well above the commutation rate — a common rule of thumb is 10× or more — so timing and current regulation stay accurate between steps.
References
- Microchip AN885 — Brushless DC (BLDC) Motor Fundamentals
- Microchip AN857 — Brushless DC Motor Control Made Easy