Tahar Hamiti

Comparison Between Finite-Element Analysis and Winding Function Theory for Inductances and Torque Calculation of a Synchronous Reluctance Machine

This paper compares the prediction of two independent methods for calculating electromagnetic torque and inductances of a synchronous reluctance machine under linear condition. One method is based on winding function analysis (WFA) and the other on finite-element analysis (FEA). Both methods take into account the rotor geometry, the stator slot effects and the stator winding connections. The simulation results obtained by the WFA are compared with the ones obtained by two-dimensional FEA. It is shown that the two methods give approximately the same results but require different computation times.

Modeling of Different Winding Configurations for Fault-Tolerant Permanent Magnet Machines to Restrain Interturn Short-Circuit Current

This paper describes an analytical model to evaluate the short-circuit (SC) current resulting from an interturn fault by computing the self and mutual inductances under SC fault condition. Two different concentrated winding configurations, i.e., horizontally and vertically placed conductors in the slot of a fault-tolerant permanent magnet synchronous machine are considered. By computing the associated slot-leakage and air-gap fluxes, the self inductance of both healthy and faulty windings as well as the mutual inductance between them, the SC current can be determined for any position and number of shorted turns. The proposed model is verified with finite-element analysis and validated experimentally. It will be shown that the magnitude of an interturn SC current depends on both the number of shorted turns and their position in the slot. The measured SC inductance shows that a new proposed concentrated vertical winding configuration can inherently limit the SC current and reduce its dependence on the position within the slot.

Feasibility and electromagnetic design of direct drive wheel actuator for green taxiing

This paper considers the feasibility of equipping the main landing gears with electric motors for the aircraft traction during the taxi phase. Those electromechanical wheel actuators make possible a “Green Taxi” operation by considerably reducing the on-ground carbon emission. Moreover, this will enable important fuel saving for short distance flights with high frequency of landing and take-off. In this work, direct drive wheel actuator is considered for energy efficiency and mechanical reliability. Two possible locations of the actuator are examined and the weights of the corresponding electric machines are compared. The most weight efficient location is then selected. A high torque density permanent magnet machine is then designed to fit in this envelope and to satisfy peak torque, weight and flux weakening capability requirements. The design procedure as well as several technologies adopted to maximize the torque density are presented.

Estimation of Eddy Current Loss in Semi-Closed Slot Vertical Conductor Permanent Magnet Synchronous Machines Considering Eddy Current Reaction Effect

This paper presents an analytical methodology based on subdomain field model to calculate eddy current loss in vertical conductor windings (VCWs) of surface mounted, radial flux, permanent magnet (PM) machines considering the current penetration effect. The proposed model can be used with any slot-pole combination including fractional slot machines having VCW. Initially, the model solves the two-dimensional problem based on the Laplaces and Poissons equations using the separation of variables technique for each of the subdomains: PM, airgap, slot opening, and slot. Then, based on that obtained solution, the eddy current reaction field in the slot is calculated by solving complex Helmholtzs equation. The validity and accuracy of the model is verified using finite-element (FE) analysis. The limitations of analytical method are discussed.

Demagnetization Analysis for Halbach Array Configurations in Electrical Machines

This paper proposes and investigates an analytical method for assessing the risk of potential irreversible demagnetization in the permanent magnets (PMs) of electrical machines equipped with n-stages, Halbach arrays. The higher risk of demagnetization, synonymous with Halbach arrays, imposes that the method be both load and temperature dependent. In fact, the proposed method studies the magnetic field distribution in the air gap and PM region, for various operating temperatures and expresses these fields as analytical expressions for the no-load and peak-load conditions. The model can cater for Halbach arrays with up to n stages, thus making it a versatile tool that can be utilized for various Halbach configurations. Finite-element analysis is used to validate the method. The analytical tool is then used for the design and analysis of a high torque density, outer rotor, traction motor. The motor is for an aerospace application and its operating duty cycle imposes very high, short-time, peak-load conditions at elevated temperatures, posing an elevated risk of irreversible PM demagnetization. The model is used to investigate various Halbach configurations for this application, in order to reduce the demagnetization risk and also to improve the general performance of the machine. The analytical method thus provides a computationally efficient tool that can be used to predict and prevent demagnetization in Halbach-equipped electrical machines operating in harsh environments such as the aerospace sector.

Torque density improvements for high performance machines

In this paper, the main aim is to propose and investigate possible methods for extending and improving the torque density capabilities of high performance, electrical machines. This is achieved by combining performance enhancing strategies such as the use of an outer rotor, the use of cobalt iron laminations and the adoption of high performance winding arrangements into a structured methodology that details the potential improvements step by step. A main point of interest of this paper is the permanent magnet demagnetisation analysis, resulting in the adoption of an optimum arrangement of a five stage, full-Halbach array. The above is presented in terms of an electrical machine used as an in-wheel motor in an aircraft traction application.

A Simple and Efficient Tool for Design Analysis of Synchronous Reluctance Motor

We present an efficient tool for design analysis of a synchronous reluctance motor (SynRM). We use winding function analysis (WFA) instead of finite-element analysis (FEA). With WFA, parameter sensitivity can be analyzed and the effects of parameters on the machine design can be evaluated very rapidly (under linear condition). We investigated the effect of rotor skewing, stator winding chording, pole arc, and interpolar air-gap length on average torque and torque ripple. We compare the results obtained by WFA with those obtained by 2-D FEA. We show that the two methods give approximately the same results but WFA requires less computation time.

Development of an aircraft wheel actuator for green taxiing

In this paper, the design and construction aspects of a wheel actuator to be used for aircraft taxiing on the ground and which will be located in the main landing gear are addressed. The main challenges with the application are the high torque density and fault tolerance requirements. This paper will look at all the different design aspects of the traction motor required for the actuator, including the electro-magnetic design and analysis, thermal management and mechanical analysis. The paper will then conclude with a brief overview of the construction aspects of the motor of the wheel actuator and experimental validation.

Thermal design of a permanent magnetic motor for direct drive wheel actuator

A permanent magnet motor was designed for aircraft traction during the taxiing phase. In order to improve the reliability, the motor was attached to enable direct drive of the wheel without additional gearing. Due to the high torque needed for the aircraft traction, and the space and mass limitations of the wheel environment, the thermal management of the motor presents a big challenge. This paper describes the thermal management of the direct drive motor. Computational Fluid Dynamics (CFD) and lumped parameter thermal models were applied to predict and improve the thermal performance of the motor. Experimental testing provided thermal data, which was compared with the lumped thermal model and the CFD results.

Comparative design analysis of Permanent Magnet rotor topologies for an aircraft starter-generator

This paper presents a comparative design study on Permanent Magnet (PM) rotor topologies for high speed aircraft starter-generators. The application requirements associated with the aircraft starter and generator operation is highlighted. Different rotor design concepts are investigated whilst keeping both the stator and the rotor diameter consistent. In addition, the core material, the electrical and magnetic constraints and the thermal and structural limitations are also kept consistent as the basis for comparison of different rotor topologies in this study. The performance of different optimal rotor designs is evaluated with Finite Element (FE) simulations and the results are presented in this paper. A Surface mounted PM (SPM) machine and a Spoke type PM machine designs are manufactured to demonstrate its ability to produce the required performance.