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SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

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That the rotor-stator flux linkage is triangular is certainly intuitive and in agreement with Figure<br />

C.14 but it seems a bit out of place, considering all of the other results (including the next case)<br />

have been squarewaves or sinusoids. An explanation will be given soon but first the sinusoidal<br />

winding with the squarewave rotor is investigated. The sinusoidal winding and squarewave rotor<br />

are shown in Figure C.16.<br />

Figure C.16 – Sinusoidal winding and squarewave rotor.<br />

There are several ways to proceed but they are all very similar to the previous derivations.<br />

Different authors take different approaches; in approximate order of formulae complexity: [69,<br />

p.6.8], [68, p.180], [26, p.462]. These proofs are not recreated here. The result is simple: the<br />

sinusoidal winding does not link any harmonics of rotor flux and the fundamental of rotor flux<br />

that it does link is only /4 of that linked by the CFP, as found earlier in the MMF section and<br />

after Equation (C.17) was derived. Since the fundamental of the squarewave is 4/ the two<br />

factors cancel and the rotor-stator flux linkage is that given by Equation (C.19).<br />

( ) NDY B cos( ) (sine winding, squarewave rotor flux) (C.19)<br />

R r p r<br />

The rotor-stator flux linkages (or peak value) are summarized below for the four winding and<br />

rotor combinations studied.<br />

(C.14): ( ) NDY B cos( ) (CFP winding, sine rotor flux)<br />

R r p r<br />

<br />

(C.17): R( r) NDY Bpcos(<br />

r)<br />

(sine winding, sine rotor flux)<br />

4<br />

<br />

(C.18): R NDY Bp<br />

(CFP winding, squarewave rotor flux)<br />

2<br />

(C.19): ( ) NDY B cos( ) (sine winding, squarewave rotor flux)<br />

R r p r<br />

297

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