Control of Synchronous Motors

Chapter 2

Optimal Supply and Synchronous Motors Torque Control: Designs in the a-b-c Reference Frame ¹

2.1. Introduction: problems of the controls in a-b-c

Chapter 1 of this book presented synchronous motors‘ modeling. The reader can find there an overview of the control problem (see sections 1.1 and 1.2, as well as [LOU 99]). This chapter utilizes the “direct models” written in the “natural reference frame”, i.e. in the “a-b-c reference frame”. It is logical to essentially consider the case of “non-salient pole” machines, particularly well adapted for representation in this reference frame. This restriction has the advantage of prioritizing “conventional controls”, adapted to “sinusoidal field distribution” machines (sections 2.2. to 2.4). This restriction also leads to powerful extensions.

Indeed, these strategies can be “extended” to – common but less conventional – controls, such as the controls of “trapezoidal field distribution” machines (or brushless DC motor), but also “advanced controls” applied to really “non- sinusoidal” machines (see sections 2.2.2, 2.2.3 and 2.3.2). We will thus conclude this chapter with a very complete presentation of original and efficient methods to optimize the supply of non-sinusoidal field distribution motors (see sections 2.5 and 2.6).

Most of this chapter will be devoted to the often critical examination of torque controls carried out by three-phase current regulations (section 2.3). We will see the limits of the classical controllers. Among ...