3-Phase BLDC Motor Sensorless Control Using MC56F8013

Control Theory2.3.3.2 Effect of Mutual Phase CapacitanceFigure 2-8. Detail of Mutual Inductance EffectThe negative effect of mutual inductance is not the only one to disturb back-EMF sensing. So far, themutual capacitance of the motor phase windings has been neglected in the motor model, since it affectsneither the phase currents nor the generated torque. Usually, the mutual capacitance is very small. Itsinfluence is significant only during PWM switching, when the system experiences very high du/dt.The effect of the mutual capacitance can be studied using the model shown in Figure 2-9Figure 2-9. Mutual Capacitance Model3-Phase BLDC Motor Sensorless Control using MC56F8013, Rev. 022 Freescale Semiconductor