Asynchronous Performance of Slitted Rotor Reluctance Machines¿Effects of Copper Conductors

Krishnamoorthy, B.M.; Krishnamurthy, M. R.

doi:10.1109/taes.1983.309449

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“…Any nonlinear treatment of the problem must necessarily be one dimensional to minimize the complexities involved. Accordingly, the assumptions made earlier regarding current, flux densities, and magnetizing forces in linear analysis [1] hold good here also. The coordinate system used is shown in Fig.…”

mentioning

confidence: 60%

“…It must be noted that k, is an impedance factor which, when multiplied by the dc resistance of the rotor converts it to its effective impedance at its working slip. As revealed by linear theory [1], characteristic curves based on limiting nonlinear theory also bring out the following. 1) When axial slits are provided on eitiier pole arcs or slots with their depths equal to slot depth, the rotor equivalent conductor in the direct axis behaves as a twostepped one [1] for which 132 is equal to P1i and D22 = 0 For a given slip, while DI1 decreases, 1P increases with an increase in the number of slits; consequently an improvement in rotor power factor and hence in the developed torque is obtained with an increase in the number of slits.…”

Section: Discussionmentioning

confidence: 86%

“…As in the case of linear analysis [1], a four-stepped equivalent conductor is considered first, and from this specific cases of rotors tested are deduced. Consider an infinite half-space of iron excited at the surface by a magnetizing force h(t) = H1(O) sin wt.…”

Section: Discussionmentioning

confidence: 99%

“…Following [ 1], the rotor impedance at rotor frequency in stator turns per phase for bar conductor of length I and width Tj can be written as Zr = (4ml Neffhr D) (4/iTh1) . [P, (N2+M2)"2/K2] (T/T ) 4e + jsXli (15) where X,i is the self-leakage reactance for the rotor iron at stator frequency and stator turns per phase and Ks is the spread factor for the assumed rotor current distribution [11. The power factor angle 4Pe of the equivalent conductor is 4ke = tan 1 (-NIM).…”

Section: Discussionmentioning

confidence: 99%

“…2) When slits are provided in both pole arcs and slots, the direct axis equivalent conductor can be shown [1] to behave as a three-stepped one in the majority of cases. With an increase in the number of slits, 131 and 12 will increase while D11 decreases.…”

Section: Discussionmentioning

confidence: 99%

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Asynchronous Performance of Slitted Rotor Reluctance Machines: Saturation Effects

Krishnamoorthy

Krishnamurthy

1983

IEEE Trans. Aerosp. Electron. Syst.

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Analytical investigation based on limiting nonlinear theory presented here for the asychronous performance of a slitted solid iron rotor reluctance machine include the effect of rotor iron saturation. Characteristic curves depicting nondimensional expressions developed for the rotor impedance factor and the power factor enable a visualization of the effects of 1) ratio of depth of saliency to depth of penetration, 2) slit number and depth, and 3) effective resistivities and saturation flux densities of different regions of the rotor on rotor parameter variations. Further predicted values are compared with experimental values and conclusions are drawn. ManuscriptIt is well known that the solid iron rotor of a reluctance machine works under saturation. This paper examines a method of analysis that takes into account the nonlinear magnetization characteristics of the rotor material. Any nonlinear treatment of the problem must necessarily be one dimensional to minimize the complexities involved. Accordingly, the assumptions made earlier regarding current, flux densities, and magnetizing forces in linear analysis [1] hold good here also. The coordinate system used is shown in Fig. 1.A novel approach for computing the effect of saturation in the iron loss of ferromagnetic material was suggested earlier [2] and is now well known as limiting nonlinear theory. The given magnetic material is then replaced by one having the nonlinear magnetic characteristics shown in Fig. 2. ANALYSIS As in the case of linear analysis [1], a four-stepped equivalent conductor is considered first, and from this specific cases of rotors tested are deduced. Consider an infinite half-space of iron excited at the surface by a magnetizing force h(t) = H1(O) sin wt.(1)The mechanism of polarization of the core is as follows. During a positive half-cycle the core gets polarized to +BS, layer by layer, to a maximum depth Dm at the end of the half-cycle, the polarization always proceeding inward from the external surface. The process repeats itself during a negative half-cycle, when the core is polarized to -Bs. Hence at any time the core can be divided into two regions, one in which the flux density has changed into + Bs and another one below it which has yet to undergo'a change. The demarcation layer is called the layer of separation; the process of magnetization can then be recognized as a movement of that layer from the external surface to a depth Din. The magnetizing force at the layer of separation is zero.Consider now the layer of separation at a distance x from the surface at time t during a positive half-cycle.The flux density above x is +Bs and that below x is -Bs. Hence the flux per unit length at time t is given by +(t) = Bs x + (-Bs) (Dm -x) = Bs(2x -Din). (2) The induced emf in all layers above that of the layer of separation is e(t) = -(a/at) +~(t) = -2B, (dxldt). The magnetizing force is zero at the layer of separation and hence H1(O) sin wt = h(t) = -[e(t)/P] x = 2 BIP X dxldt.(3) Equation (3) governs the movement of the layer of separa...

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confidence: 60%

Section: Discussionmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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