Air-Cored Resonant Induction Machines: Comparison of Capacitor Tuning Criteria and Experimental Validation

IEEE Trans. on Ind. Applicat.

et al. 2022

Self Cite

The air-cored resonant induction machine removes the magnetic core so the fields produced by the windings are truly 3-D in nature. The end-windings normally regarded as a non-active and leakage source in conventional iron-cored machines now become an active part and contribute to the torque production. Therefore, the electromagnetic modeling can no longer be reduced to a 2-D analysis and the 3-D inductance calculation becomes a key problem. The 3-D Finite Element Analysis (FEA) can solve the 3-D magnetic field but, firstly, the validity of its solution depends on the precision in geometry modeling. In particular, representing the end-winding region avoiding conductor clashing can be very complicated. Secondly, 3-D FEA solutions are computationally-slow and therefore inefficient as an "internal routine" of an optimization procedure. This paper proposes a fast analytic 3-D winding inductance estimation method for air-cored resonant induction machines. The approach breaks down the real coils into straight conductors and represents them by single filaments located at their centers, then uses closed-form expressions derived from Neumann integrals to calculate the coil self and coil-to-coil mutual inductances which are then collected into winding phase self and mutual inductances. All the independent coil-pair contributions are isolated so as to eliminate redundant calculations. Good accuracy of the calculated results is confirmed by validation against both 3-D FEA and experimental results, including winding inductance breakdown and overall machine tested performance.

Section: Testing and Results Comparisonmentioning

confidence: 99%

Section: Takedown Policymentioning

confidence: 99%

A Fast 3-D Winding Inductance Estimation Method for Air-Cored Resonant Induction Machines

IEEE Trans. on Ind. Applicat.

et al. 2022

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“…The steady-state per-phase equivalent circuit of ACRIMs with both stator and rotor capacitors has been derived and validated in [10] and is shown in Fig. 1, where the stator and referred rotor resistances are Rs and r R′ respectively, the stator leakage, magnetizing and referred rotor leakage reactances are Xls, Xm and lr X ′ respectively, the stator capacitor and referred rotor capacitor reactances are XCs and Cr X ′ respectively.…”

Section: A Equivalent Circuitmentioning

confidence: 99%

“…2-D FE validations are included in the paper but only for a stationary rotor fixed at different angles and no experimental confirmation is provided for the operating principle. [8]- [9] compare four different capacitor tuning criteria and propose an ACRIM configuration using stator capacitors only, [10] presents the experimental validation of the tuning option on a spinning ACRIM prototype. However, [8]- [10] do not cover the design procedure.…”

Section: Introductionmentioning

confidence: 99%

“…[8]- [9] compare four different capacitor tuning criteria and propose an ACRIM configuration using stator capacitors only, [10] presents the experimental validation of the tuning option on a spinning ACRIM prototype. However, [8]- [10] do not cover the design procedure. Considering there is no magnetic core in air-cored machines and therefore the magnetic field is inherently 3-D, [11] proposes a fast 3-D inductance estimation method for ACRIMs using closed-form expressions without relying on the computationallydemanding 3-D FEA, but the design optimization of ACRIMs is not discussed.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Design Optimization Procedure of Air-Cored Resonant Induction Machines

2021 IEEE Energy Conversion Congress and Exposition (ECCE)

et al. 2021

Self Cite

The air-cored resonant induction machine removes the iron core which makes its magnetic field truly 3-D in nature. The axial conductors and end windings now both become active components contributing to torque production. The whole winding therefore needs to be considered in the design process. Conventional 3-D finite element analysis has large computational costs and is hard to integrate into the design optimization. This paper presents a new design optimization procedure for air-cored resonant induction machines using closed-form solutions of Neumann integrals which are computationally fast and considers the 3-D magnetic field distributions created by the air-cored coils. Optimized designs for two tuning options in the literature: option I with stator capacitors only and option II with both stator and rotor capacitors, are presented. The optimization trends with respect to different machine parameters are also discussed.

A Combined 3-D Geometric and Magnetic Modeling Approach of Coils in Air-Cored Resonant Induction Machines

2022 IEEE Energy Conversion Congress and Exposition (ECCE)

et al. 2022

Because of the air-cored and toothless structure, ACRIMs usually have coils with flat cross-sections and need 3-D inductance evaluation. Since the precision in geometry modeling is vital to the inductance-estimation accuracy, a combined geometry modeling and inductance calculation method is proposed. The coil geometry construction process can handle non-circular cross-section and complex coil shapes, it generates a single-or multi-filament model ready for analytic inductance calculation and coordinates information for 3-D FEA modeling. Based on the closed-form solutions for the mutual inductance of two straight segments placed at any orientation in 3-D, the filament-level, conductor-level, coil-level and winding-level inductances can be calculated, the entire calculation procedure is fast, accurate and avoids numerical singularities so is suitable to be incorporated into an optimization program. Good correlation is confirmed in validation against 3-D FEA results on an air-cored resonant induction machine design.