1.5.3 Phase Angle Correction

The phase angle (rotor position) is computed from the phase current measurements taken in previous cycles. The phase currents measured at the beginning of the control loop cycle are produced by the corresponding voltages applied in the previous cycle. These currents and these voltages are used to estimate the phase angle, which is used to determine the phase voltages for the next cycle.

The total delay is comprised between one and two sampling periods therefore, the error in the phase estimation is shown in the following equation.

$\mathrm{\Delta }\mathrm{\Phi }=k\omega T_c,1\le k\le 2$

When the speed is low, the error is negligible, but when the speed is high it is necessary to keep it into account (i.e., 18000 rpm in a 4 poles motor means 3770 rad/s, with PWM Frequency of 10 kHz, with k = 1.5, 0.565 rad that is 32.4°).