sixstep

SixStep is a motor control technique primarily used for three-phase brushless DC motors (BLDC) and, in some contexts, permanent magnet synchronous motors (PMSM). Also referred to as six-step commutation or trapezoidal commutation, it energizes two of the three stator windings at a time in a rotating sequence, creating a coarse rotating magnetic field. Each state corresponds to about 60 electrical degrees, and six distinct states complete one electrical cycle.

In operation, rotor position is used to select the active windings. Sensor feedback may come from Hall sensors or, in sensorless implementations, from back-EMF in the unenergized phase. The approach yields a simple drive that can be implemented with basic microcontrollers and pulse-width modulation, making it attractive for low-cost or space-constrained systems.

Advantages of six-step control include its simplicity, low component count, and permissive sensor requirements. It generally works well for basic applications and provides robust startup and operation in many environments. Disadvantages include torque ripple and audible noise due to the coarse, trapezoidal torque profile, as well as higher harmonic content compared with sinusoidal control methods. This can lead to lower efficiency and smoother operation at certain speeds, particularly at light load or high speed.

History and usage: six-step control became common in early BLDC drives and remains prevalent in low-cost or compact drives where simplicity and cost are priorities. While many modern drives employ sinusoidal or field-oriented control for improved smoothness and efficiency, six-step remains a viable option for sensors or processing-limited systems and for applications that tolerate torque ripple.

See also: brushless DC motor, trapezoidal control, sinusoidal control, field-oriented control, PWM.