Drive Principles

Abstract

In successive chapters extensive attention will be given to the modeling and control of rotating field machines. Rotating field machines can be conveniently modeled with the aid of a so-called ideal rotating transformer (IRTF). The initial part of this chapter explores the IRTF concept. It will be shown that torque production may be described mathematically by the cross product of a flux and current space vector. In the previous chapter, three-phase current control was introduced with the precise aim of being able to manipulate the current space vector. The reason for this approach is to develop a set of fundamental drive concepts which aim to, at an elementary level, control torque in drive systems based on rotating field machines such as synchronous or asynchronous machines. Application of the IRTF concept for brushed DC machines is also possible, though it is not widely used and will not be discussed in detail. Note that switched reluctance machines do not embrace the Lorentz force based concept, which implies that they do not follow the IRTF model and therefore they are treated separately in this book at a later stage.