TABLE OF CONTENTS J. Kirtley
This section introduces the design evaluation of permanent magnet motors, with an eye toward servo and drive applications. It is organized in the following manner. First, three different geometrical arrangements for permanent magnet motors are described:
Surface-mounted magnets, conventional stator.
Surface-mounted magnets, air-gap stator winding.
Internal magnets (flux-concentrating).
The section then includes a qualitative discussion of these geometries. Also examined is the elementary rating parameters of the machine and how to arrive at a rating, how to estimate the torque and power vs. speed capability of the motor, how the machine geometry can be used to estimate both the elementary rating parameters; and finally, the parameters used to make more detailed estimates of the machine performance.
There are, of course, many ways of building permanent magnet motors. However, only a few will be considered in this section. Actually, once these are understood, rating evaluations of most other geometrical arrangements should be fairly straightforward. It should be un- derstood that the rotor inside vs. rotor outside distinction is in fact trivial, with very few exceptions.
Figure 6.1 shows the basic magnetic morphology of the motor with magnets mounted on the surface of the rotor and an otherwise conventional stator winding. This sketch does not show some of the important mechanical aspects of the machine, such as the means for fastening the permanent magnets to the rotor, and so one should look at it with a bit of...
