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^1 POLITECHNIKI WARSZAWSKIEJ

Eąuation (1.14) may be written as:

transformation rotation voltage voltage

8y di dy. A6 U, = r i. + ^L—- + — .

0ij dt 50 dt

(1.17)

5y/,

Denoting —^L as the transient (dynamie) inductance L,:

di:

5y/_} (^,ij)

di.

(1.18)

The last term in (1.17) represents the back emf. Ej:

E; = -^L(0.

^J 50

(1.19)

So (1.17) becomes:

dii

U: =r_sij +L_i(6>,i = )—^ + E_i(cy,6>,i_i). dt

(1.20)

An equivalent circuit with time dependent parameters may be defined based on eąuations (1-20) - (Fig. 1.7).

^r= Lij(C. *j)

-VWV-

Ul

Rcs Jjr

-;Rc

Fig. 1.7. Equivalent circuit of SRM with core losses.

The core losses are represented by the variable resistances in parallel with the emf E, based on the assumption that only the main flux produces core losses. Core losses occur in the stator and in the rotor core as this machinę does not operate on the traveling field principle. Especially in high speed applications (above 6000 rpm) core loss has to be considered not only for efficiency calculations but also in the transient current responses assessment.

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