SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

Therefore, to achieve linear control over torque in a nonsalient machine requires that the d-
component of commanded current be controlled as well to the q-component. To control a salient
machine with FOC, the torque constant K T in the q-circuit must be replaced with the function
block to control both d- and q- circuits, as shown in Figure 5.18. The type of motor and controller
would determine the nature of the function block. In the simplest case it would be a simple
function of fixed motor parameters, but in practice it may perhaps be a function of load (speed
and current) or other variables.
Figure 5.18 – Current command generator for FOC of salient motor.
Finally, it should be noted that there are many different (and conflicting) terms used to describe
the rotors shown in Figure 5.15 [68], [69], [42], [41]. The magnets in Figure 5.15-a are nearly
always called surface mounted; they can take on arbitrary shape, pitch, thickness, or
magnetization profile. The magnets in Figure 5.15-b are called circumferential, radial, or spoke,
magnets and those in Figure 5.15-c are called inset magnets; both are examples interior magnets.
Many other types of rotors exist; the ones shown above were selected only to show the
differences in saliency. However, one additional type of interior magnet rotor (often called a
buried permanent magnet rotor) that appears quite often in the literature is shown in Figure 5.19.
The magnets are completely contained in the rotor steel laminations and this allows the rotor to
operate at very high speeds without the possibility of the magnets flying off (the other varieties
shown may have a magnet that is bonded to the rotor or wrapped in a nonferrous retainer [69],
[68]).
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