The single-phase capacitor induction motor of 1.1 kW, 230 V, employed for stand-alone generating operation has 4 poles and 30 skewed rotor bars. The ratings of the induction machine are listed in .

Table 1 Ratings of the single phase induction machine

Taking into consideration geometrical symmetry and electromagnetic periodicity of the machine, two-dimensional magnetic field computation of the generator was reduced to two pole pitches of the cross-section. The FE model of the generator accounts for nonlinear magnetizing characteristic of the magnetic core (Figure 1) and skin-effect in the rotor bars. The finite element mesh of the generator (Figure 2) was built of 11244 second-order triangular and quadrangular elements

Figure 1 Magnetization characteristic of magnetic core of tested induction machine

Figure 2 FE mesh of 2D field-circuit model of the SPSEIG

The 2D magnetic field in the induction generator is determined by the equations:

$$\begin{array}{}{\displaystyle \mathrm{c}\mathrm{u}\mathrm{r}\mathrm{l}\left(\nu \cdot \mathrm{c}\mathrm{u}\mathrm{r}\mathrm{l}\mathit{A}\right)=\left\{\begin{array}{ll}{\mathit{J}}_{S}& \text{in stator windings}\\ {\mathit{J}}_{b}-\sigma \cdot \mathrm{\partial}\mathit{A}/\mathrm{\partial}t& \text{in rotor bars}\\ 0& \text{in air, iron core and shaft}\end{array}\right.}\end{array}$$(1)

where *A*[0, 0, A(x, y, t)] is the magnetic vector potential, *J*_{s}[0, 0, *J*_{s}(x, y, t)] – the current density in the stator slots, *J*_{b}[0, 0, *J*_{b}(x, y, t)] – the current density in the rotor bars, *ν* – reluctivity of magnetic material, *σ* – electric conductivity. Two-dimensional field equations coupled with voltage equations of stator and rotor windings [5] were solved simultaneously to obtain voltages and currents induced in the stator and rotor. Having the variables *A* and *J* computed, the other quantities of electromagnetic field as magnetic flux, magnetic induction, etc. may be determined taking into account the magnetization characteristic of iron magnetic core of the generator. Furthermore it was also assumed, that iron core losses in the field-circuit simulation model of the generator were neglected.

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