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SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

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vAN R iA LM iA eA d<br />

v<br />

<br />

<br />

<br />

R<br />

<br />

i<br />

<br />

<br />

<br />

LM <br />

i<br />

<br />

<br />

<br />

e<br />

<br />

BN B B B<br />

dt <br />

vCN R i C LM i C e C <br />

(B.13)<br />

However, the voltages are true line-neutral voltages (by definition). If a grounded neutral were<br />

used these voltages would simply be the terminal voltages ( vAM, vBM, v CM)<br />

because the neutral<br />

would be at zero potential. The same is true when common-mode/zero-sequence component is<br />

not present in the applied voltages (see Appendix D). However, if ZS components are present the<br />

terminal voltages must be used instead of the line-neutral voltages by using the “phase<br />

interference matrix” (Appendix D).<br />

Now this result will be specialized for the sinusoidally distributed winding which this report<br />

assumes. From this point on only the matrix of inductances will be manipulated to save space.<br />

Including the magnetizing inductance (Equation B.6) yields Equation (B.14).<br />

( Lmag L ) M<br />

<br />

<br />

<br />

( Lmag L) M<br />

<br />

( Lmag L ) M<br />

<br />

(B.14)<br />

If the windings are sinusoidally distributed the mutual inductance between is given by Equation<br />

(B.15) [28, pp.251,654], [69, p.6.8].<br />

M L cos( )<br />

(B.15)<br />

mag<br />

<br />

For a three-phase machine 120<br />

thus the mutual inductance is given by Equation (B.16).<br />

M Lmag<br />

cos( 120 )<br />

1<br />

(B.16)<br />

M Lmag<br />

2<br />

It is worth noting that using 0 in Equation (B.15) gives the airgap portion of the self<br />

inductance of a winding. This emphasizes that the mutual inductance is a result of magnetizing<br />

flux. 44 Substituting the result of Equation (B.16) into Equation (B.14) yields Equation (B.17).<br />

44 There is also a slot leakage component of mutual inductance but it is usually negligible [28, p.251].<br />

275

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