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SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

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For the sine rotor it is clear to see that the sine winding linked only /4 the flux that did the<br />

CFP winding as expected, but since there were no rotor flux harmonics we do not see any<br />

harmonic filtering action. For the sine winding and squarewave rotor it is seen that all harmonics<br />

are filtered, and per the above discussion above we see that the fundamental is again reduced by<br />

/4.<br />

The result that is not obvious is that the CFP winding “passes” all harmonics of rotor flux<br />

(that is, it links all harmonics) but each is attenuated.<br />

In other words, we saw that the CFP winding generated unit-amplitude fundamental MMF and<br />

the maximum possible MMF amplitude of each harmonic (but these were less than unit<br />

amplitude); the sine winding did not generate the MMF harmonics but produced a loweramplitude<br />

fundamental MMF. The similar situation here is that the CFP winding links the full<br />

value fundamental of rotor flux and links to the fullest extent all harmonics present in the rotor<br />

flux (but these linkages are less than unit amplitude); the sine winding did not link the rotor flux<br />

harmonics but links a reduced amount of the fundamental of rotor flux. The parallel statements<br />

for MMF and rotor-stator flux linkage indicate that the winding distribution influences MMF<br />

production and rotor-stator flux linkage in similar ways. It turns out that the effect on each is<br />

identical and is thus described in terms of the fundamental and harmonic winding factors.<br />

Whereas the winding restricts harmonics from the CFP in the case of MMF (Figure C.11), it<br />

restricts the harmonics from the rotor flux in the case of rotor-stator flux linkage (Figure C.17). It<br />

should now be very clear that the rotor flux and winding distribution interact in space to produce<br />

the rotor-stator flux linkage and Figure C.1 should be reviewed in comparison with Figure C.11<br />

and Figure C.17.<br />

298

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