To address the problem of high-frequency ac loss of hairpin winding, a hybrid transposed hairpin winding (HTHW) scheme, which combines flat wire and litz wire, is proposed. The HTHW can effectively reduce the high-frequency ac loss, while maintaining a relatively high slot fill factor. In this article, the ac loss generation mechanism under high-frequency excitation is first analyzed. Then, based on the field-circuit-coupled finite element method, the current density distribution, and ac loss of hairpin winding with different transposed topologies are calculated and compared. Finally, an experimental platform enabling direct measurement of hairpin winding loss is built to verify the simulation. The simulation and experimental results show that the ac loss of the proposed HTHW is much lower than that of the traditional hairpin winding, for medium to high running frequency. In our case, the ac and dc resistance ratio of the presented HTHW is 2.12 at the frequency of 1200 Hz, contrasting that of the ratio of traditional hairpin winding, which is 10.2.

This article proposes an interturn short-circuit fault diagnosis method for permanent magnet synchronous machines for electric vehicles based on search coils (SC) with a unique structure. In this proposed structure, the SCs are uniformly wound in the main flux direction of each phase, and the number of SCs is twice the number of phases, resulting in significant cost savings. Based on this structure, a novel fault feature based on the negative-sequence components of the second carrier frequency sideband harmonics in the voltage signal of the SC is proposed. As a result, this fault characteristic frequency component is not only more obvious than the fundamental component used in the traditional SCs method but also can be transformed to a dc indicator by two coordinate transformations, which is conducive to online implementation in both stationary and nonstationary conditions. Finally, experiments are presented to verify the proposed diagnosis strategy.

SiC mosfet is a promising power device for electric drive system due to its various advantages such as high switching frequency and low loss. However, fast switching speed results in high voltage stress and can potentially cause insulation damage of the winding. Few studies have analyzed and evaluated the voltage stress, especially for the hairpin winding, which is the mainstream winding type for electric vehicle traction machines. For this purpose, this article proposes a high frequency equivalent circuit model to predict the interturn voltage stress of hairpin windings driven by SiC mosfet s. First, the working principle of the overvoltage at the winding ends is analyzed and validated by experiments. Then, the parasitic parameters are calculated before building the high-frequency equivalent circuit. A field-circuit coupled finite element method is used to consider the nonlinear parameters and to evaluate the voltage stress. Finally, a prototype is built, and the voltage stress is tested. The resultant error between the calculated and experimental maximum interturn voltage stress is only 1.3%, which supports the inference on the validity of the presented equivalent circuit and the method. Based on the above, a novel winding connection scheme is proposed to reduce effectively the voltage stress of hairpin winding.

Conventionally, the magnetic core in an inductive power transfer (IPT) system is spliced by pieces of ferrites, which is time-consuming and unable to realize a seamless fit on the curved surface. This letter proposes a compact curved coupler with a novel flexible nanocrystalline flake ribbon (NFR) magnetic core. Compared with ferrite core, the NFR not only enhances the application flexibility of the IPT system but also significantly reduces its weight in certain power. Based on the LCC -S compensation topology, a 1 kW IPT prototype for autonomous underwater vehicles is fabricated. The transmission characteristics and temperature performance of the system have been investigated under three power levels, considering various permeability values for NFR cores. Finally, the NFR with a permeability of 800 is chosen as the magnetic core, and the dc–dc system efficiency reaches 92.85%. Moreover, it is possible to restrict the maximum temperature to 54.1 °C, and the weight of the NFR cores accounts for merely 4.65% of the whole coupler.

In this article, a novel rotor fault diagnosis and separation approach based on search coils (SCs) for permanent magnet synchronous motors is proposed. First, the SC setup is introduced along with its working principle and spatial arrangement. Based on this special structure, the local magnetic field distortion caused by the local demagnetization fault (LDF) of permanent magnets or the dynamic eccentricity fault (DEF) can be accurately diagnosed. The fault characteristics of both LDF and DEF are the existence of fractional harmonics in the SC induced voltage signal. Compared to the traditional phase back electromotive force method, these features do not depend on the motor pole-slot combination and are not be hidden due to periodic overlap. Second, to distinguish between two faults with similar characteristics and considering the inherent errors of healthy motors due to processing tolerances, two random forest (RF) models are chosen to gain automated classification. Finally, to simplify the model and improve diagnostic efficiency, the features are screened and the final diagnosis scheme is established. Simulation and experimental results have validated the accuracy and the superiority of the proposed method.

Modular Cascade Machines (MCM) system is a multi-machine system for the traction systems of electrified vehicles. Currently, MCM is composed of several machines of the same type, generally, several Permanent Magnet Synchronous Machines (PMSM). This paper proposes a hybrid MCM system, which is composed of a PMSM and an Induction Machine (IM). This combination aims to fully benefit the properties of different machines. This hybrid MCM is compared with other traction systems, namely, PMSM-based MCM and single PMSM drive. For a fair comparison, the design specifications of all the traction systems are optimally sized by a specific sizing method, which can maximize the system high-efficiency area. Then, different traction systems are designed by Finite Element Method (FEM), in order to have accurate material consumptions and efficiency maps. The comparison study shows that the proposed hybrid MCM is competitive for energy saving. Therefore this new drive saves about 5% of energy in comparison with a single PMSM derive. The hybrid MCM energy saving is very close to the one of a PMSM-based MCM. Moreover, the hybrid MCM system reduces the PM volume (reduced by 53%) while increases the usage amount of winding copper, steel and aluminum, due to the existence of IM. Fortunately, the cost estimation proves that the hybrid MCM (not include inverters) has almost the same cost as the single PMSM. Hence the proposed hybrid MCM is a competitive alternative of the single PMSM than the PMSM-based MCM.