18.07.2013 Views

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

the fundamental we had observed in the sinusoidal winding (both in MMF and rotor-stator flux<br />

linkage). The factor 4/ is written in red and the factor /4 is written in blue to signify that<br />

they stem from different constraints (Bp describing maximums that are a fundamental or peak<br />

value; unity gain set by a fundamental).<br />

Finally, looking at the rotor-stator flux linkage produced, it is first interesting to note that the first<br />

and last combinations produce the same result. That is, a “sinusoidal motor” could be built by<br />

using a CFP winding and sinusoidal rotor, or by using a sinusoidal winding and a squarewave<br />

rotor. In the first combination the fundamental of rotor flux has unit amplitude but is not<br />

attenuated whereas in the second combination the amplitude of fundamental rotor flux is greater<br />

than unity but is attenuated by the sinusoidal winding. Examining the sine-sine combination, we<br />

see that only the fundamental of rotor flux is present and it gets attenuated by /4 as expected.<br />

The last combination (CFP-square) is the one for which an explanation was promised and is the<br />

most interesting. If the reader has not yet deduced it, the factors shown in the MMF column [f(θr)]<br />

of Figure C.19 are indeed the fundamental- and harmonic- winding factors. As stated earlier and<br />

as shown by Figure C.1, the role of the winding distribution (described by winding factors) is<br />

two-way in nature (MMF and rotor-stator flux linkage). The results described here are all<br />

consistent with Figure C.17. That is, the amplitude of each flux harmonic is multiplied by that<br />

harmonic’s winding factor to yield the amplitude of rotor-stator flux linkage for that particular<br />

winding-rotor combination.<br />

This is best exemplified by discussing this last winding-rotor combination. We know that for the<br />

CFP winding and squarewave rotor the rotor-stator flux linkage is given by Figure C.15-a and the<br />

peak value is given by Equation (C.18).<br />

<br />

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

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

2<br />

First, amplitudes of φ(θr) are those of the squarewave rotor flux and are known to be correct.<br />

Next, the winding factors are those of the CFP winding, which have also given correct results.<br />

The term-by-term multiplication yields the amplitudes given for ψR(θr). Earlier, Equation (C.18)<br />

was taken directly from Figure C.15-a which was derived graphically based on Figure C.14 and it<br />

is consistent will all of Chapter 2. The Fourier coefficients given for ψR(θr) are those of a triangle<br />

wave (which is why the rotor-stator flux linkage is triangular) but the multiplier is not correct—it<br />

should be<br />

2<br />

8/ . Per Equation (C.18), we already know the rotor-stator flux linkage to be a<br />

302

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!