The induction assisted permanent magnet synchronous motor (IAPMSM) is a prospective choice for the electric and hybrid electric vehicle (EV/ HEV) drivetrain due to its lower losses, high efficiency ...and constant torque over a defined frequency range. This manuscript presents a part of an ongoing research project which is motivated towards building a prototype of an industrial 7.5 hp IAPMSM. Firstly, a new analytical approach to model the IAMPSM using rotor reference frame theory is proposed. The developed 7.5 hp IAPMSM model is then analyzed through calculated results and compared with the conventional model of the aluminum-rotor induction machine (ARIM) to elicit merits and demerits of the prototype being built. This paper aims to provide a comprehensive understanding of both the machines to serve as a guideline towards prototype development.
In Surface Permanent Magnet (SPM) Synchronous machines with fractional slot concentrated windings (FSCW) configuration, few slot/pole combinations exhibit large spatial harmonic and sub-harmonic ...fields. Spatial harmonics result in distorted voltage waveforms and cause additional losses thereby deteriorating the machine's performance. From background literature, it has been found that these harmonics are reduced by increasing the number of winding layers, increasing the number of phases, or introducing complicated magnetic flux barriers in the stator core, thereby reducing the overall torque density of the machine. This paper presents a method to minimize the effects of spatial harmonics by skewing the stator windings without reducing the torque producing harmonic component. Further, the impact of stator winding skew is studied on magnetic force, open-circuit phase voltage, inductances and cogging torque using a novel analytical model incorporating higher order harmonics in air-gap flux density and phase inductances. Comparative analysis of skewed machine is performed with the experimentally obtained results for a baseline un-skewed machine.
In this era of advanced computing where complex algorithms and expensive approaches are used to determine the machine parameters of a synchronous machine, this paper proposes a novel, economical and ...yet fundamental approach towards estimation of the d- and q-axis field and damper circuit parameters of a low/medium power wound-field synchronous machine. The proposed novel methodology employs fundamental voltage, current, flux linkage relationships of the 3-phase wound-field synchronous machine in a-b-c reference frame theory. The methodology employed has been explained in length using analytical equations and experiments have been performed on a laboratory synchronous machine based on the developed method. Other equivalent circuit parameters have been determined using conventional tests. At the end, experimental findings have been presented and discussed.
Surface Permanent Magnet (SPM) synchronous machines with fractional slot concentrated windings (FSCW) have been found to provide high torque density with low torque ripple and cogging torque, making ...them suitable for direct-drive electric vehicle (EV) application. This paper initially analyses a 3-phase 36/30 FSCW SPM machine for direct-drive application in terms of its space harmonics, steady-state characteristics and losses over a wide speed range using winding function theory and MTPA control in conjunction with finite element analysis (FEA). It was found that the 3-phase machine produces high space harmonics in the flux density which resulted in increased magnet eddy current loss and high stator leakage inductance which leads to extended constant power speed range (CPSR) as well. Since, the CPSR requirement for a direct-drive EV motor is lesser than that of a high-speed EV motor, there is scope for reducing the stator leakage inductance. Hence, a 6-phase 36/30 FSCW SPM machine employing the same stator, rotor and current rating as that of the 3-phase machine is investigated in an effort to reduce space harmonics, stator leakage inductance and magnet eddy current losses while delivering the desired output characteristics. Also, an analytical method to calculate the 6-phase machine d- and q-axis inductances from winding and slot permeance functions are proposed. Thereafter, a comparative performance analysis is conducted on both the 3-phase and 6-phase machines designed and results are discussed.
In order to design and control a permanent magnet synchronous machine (PMSM) for superior performance over a wide speed range, comprehensive testing methods with accurate measurements are of ...paramount importance. Moreover, in order to extract the maximum operating capability of the machine with inverter and magnetic saturation, accurate determination of dq-axis inductances over a wide speed range is essential. In this paper, a comparative analysis of three inductance determination methods based on stand-still and moving conditions of the machine is performed. The chosen test methods for measurement and calculation of d- and q-axis inductances are validated experimentally using a laboratory interior permanent magnet synchronous machine (IPMSM) prototype. Merits and demerits of these methods are thereafter analyzed comprehensively in terms of complexity of the methodology implemented, accuracy of parameters determined taking into account effects due to harmonics and temperature, scope and applicability of each of the test methods.
Integrated charging (IC) technology in electric vehicles (EVs) employing conventional power electronics and motor drivetrain components facilitates level 3 fast charging capabilities with reduction ...in overall weight and cost of the vehicle. However, when the winding inductances of 3-phase interior permanent magnet synchronous machines (IPMSMs) are realized as line inductors for battery charging, due to machine saliency, the magnetic fields produced by the sinusoidal AC supply results in 1) asymmetrical voltages in the air-gap as a function of rotor position and 2) relatively high magnitudes of oscillating torques causing harmful noise and vibrations. This can lead to significant AC losses with risk of permanent magnet demagnetization in the machine. Since the same motor is employed for traction application as well, it is of significance to optimally design the machine for IC operation. Thus, this paper exclusively investigates three IPMSM rotor configurations to be employed for IC operation in EV. This paper firstly presents a conventional dq-axis circuit model based damper design approach implemented for mitigating the saliency effect during IC. Then, a comparative performance analysis of the rotor configurations with damper bars during IC operation on machine saliency; asymmetrical voltage waveforms; oscillating electromagnetic torque; permanent magnet operating point and magnet losses is performed using finite-element analysis (FEA). Results obtained are analyzed and discussed.
Direct-drive electric vehicle motors have requirements such as high-torque, low-speed and a constant power speed range (CPSR) between 3 and 5 depending on the tire size. Furthermore, these motors ...must deliver lower cogging torque and torque ripple when compared to conventional electric vehicle high-speed motors due to absence of any damping mechanism. Surface permanent magnet synchronous machines (SPMSMs) with distributed winding configuration are found to favor the aforementioned characteristics for the above application. However, in spite of the lower CPSR requirements for direct-drive application, SPMSMs suffer from poor flux weakening operation. Various rotor structural modifications as well as optimal PM sizing solutions are proposed in literature. However, they fail to take into account the stator slotting effect which significantly affects the flux weakening operation of the machine. Thus, in order to alleviate the challenges involved in realizing a SPMSM as a direct-drive motor, Response Surface Methodology (RSM) is implemented with magnet size and stator slot dimensions as design variables in an effort to optimize the characteristic current and further enhance the CPSR of the machine. Finite element models of the optimal machine are used to verify the output power- and torque-speed characteristics over entire operating range calculated from analytical equations.
The spatial harmonic of magnet flux is a major cause of torque ripple in permanent magnet synchronous machines (PMSMs), and it is temperature-dependent. Thus, this paper investigates torque ripple ...modeling and minimization for PMSMs considering magnet temperature variations. Firstly, experimental studies are conducted to demonstrate that the torque ripple is magnet temperature dependent. Then, based on extensive experimental tests, a novel linear model is proposed to model the relationship between the dc and harmonic components of magnet flux in the dq reference frame, which provides a way to estimate the magnet flux harmonic. Based on this model, the torque ripple model considering magnet temperature variation is proposed and validated with simulations. Afterwards, a novel adaptive current optimization approach is proposed for torque ripple minimization, which consists of two parts: the magnet flux harmonics estimation using the proposed linear magnet flux model, and the current optimization using the proposed torque ripple model. In our approach, the stator current is adaptively optimized with respect to the magnet temperature. However, the proposed approach is not necessary to run in real-time, because temperature variation has a large time constant. Our approach is validated through both numerical and experimental studies.
Removal of the gear-box from a conventional all-electric vehicle (EV) power-train and incorporating direct-drive topology is expected to improve motor-to-wheel efficiency. Firstly, this paper ...discusses the merits and challenges of a novel direct-drive scheme employing a single on-board motor in an EV. Thereafter, motor design targets established for such an application in a typical super-mini EV are discussed. A novel bottom-up approach based on maximum-torque-per-ampere (MTPA) control and winding function theories of PM machines is proposed to design an on-board direct-drive surface permanent magnet (PM) machine with fractional-slot concentrated-windings in the stator. A typical direct-drive motor is designed employing the proposed approach and its performance is analyzed using its electromagnetic model in conjunction with finite element analysis and MTPA control scheme over the entire speed range of the motor. Comparative analysis of results obtained from analytical calculations and finite element analysis is performed. It is also shown that the proposed direct-drive scheme in EV is worth considering for advancement of state-of-the-art EV drive-train systems technology.
Understanding the need for improvement in efficiency of an electric vehicle drivetrain system, this paper exclusively discusses various design aspects of a permanent magnet machine drive for ...direct-drive electric vehicles (EV). Firstly, the motivation to employ a direct-drive configuration in EV is discussed. Thereafter, initial electric machine rating design considerations for a typical Supermini or B-segment EV employing a direct-drive configuration is discussed. Furthermore, employing an existing stator, investigations are performed through analytical equations and designed machines to understand different permanent magnet machine design aspects with regards to selection of: number of poles, type of permanent magnet rotor, stator winding configuration and number of phases. The study performed here will assist in providing decision points on various structural design indices of the machine before venturing into the FEA based permanent magnet machine design and assessment for the direct-drive EV application.
