ABSTRACT
This chapter describes current sensing methods without external sensors, such as Hall effect current sensors. Sensorless methods of current commutation instances of phase windings are described by borrowing from. The drive system is dependent on the position and current sensors for control. Elimination of both the sensors is desirable in many applications, particularly in the low-cost but high-volume applications from the cost and compact packaging points of view. That makes it all the more important to do without the position sensor for the control of the Permanent magnets brushless dc machines drive system. The phase currents can be sensed from the dc link current and hence one sensor is sufficient for current control of the machine. Consider a load variation and that will slow down the motor, thereby decreasing the induced emf leading to an increase in the stator phase currents for given fixed duty cycles.
