Surong Huang

A comparison of power density for axial flux machines based on general purpose sizing equations

Based on the concept of the converter fed machine (CFM), an optimal machine design can be considered as the best match of the machine topology, the power electronic converter and the performance specification. To compare power production potential of axial flux machines with various topologies, different waveforms of back EMF and current, general purpose sizing and power density equations for such machines are needed. In this paper, a general approach is presented to develop and to interpret these equations. Sample applications of the sizing and power density equations are the axial flux toroidal permanent magnet utilized to compare the axial flux toroidal permanent magnet (AFTPM) machine and the axial flux two-stator permanent magnet (AF2SPM) machine.

Torque quality and comparison of internal and external rotor axial flux surface-magnet disc machines

In this paper, pulsating torque components of permanent magnet machines and pulsating torque minimization techniques are discussed for axial flux surface-magnet disc-type PM machines. The pulsating torque analysis describing general instantaneous electromagnetic torque equation and torque ripple factor is briefly provided in order to analyze torque ripple component. Detailed finite-element analyses focusing on the minimization of cogging and torque ripple components using several techniques are also given. A detailed comparison of the two techniques is also illustrated in this paper.

Design, Analysis, and Control of a Hybrid Field-Controlled Axial-Flux Permanent-Magnet Motor

This paper presents the design, analysis, control, and experimental evaluation of an innovative field-controlled axial-flux surface-mounted permanent-magnet machine. Topology and design equations, as well as an optimized design study, are attained. The machine is investigated in detail using finite-element analysis, and a prototype machine is built. In order to evaluate the new axial flux machine topology, an experimental system setup is devised and discussed. The experimental results of the prototype machine and a comparison between the analysis and test results are also presented.

A new axial flux surface mounted permanent magnet machine capable of field control

This paper presents a new axial flux surface mounted permanent magnet (PM) field controlled TORUS type (FCT) machine. Machine structure and principles are explored and the field weakening feature of the topology as well as the advantages of the machine are presented in the first part. The second section introduces the linear model and sizing analysis using generalized sizing equations. Optimization of the machine pole number and power density maximization for the optimum pole number is also achieved. In the third section, 3D finite element analyses (FEA) of the topology are illustrated for different field currents in order to accomplish the machine design and to determine the sizing of the optimum field winding. Furthermore, torque analysis of the FCT machine using 3D finite element analysis is also carried out and illustrated in the paper.

Design and 3D electromagnetic field analysis of non-slotted and slotted TORUS type axial flux surface mounted permanent magnet disc machines

Nonslotted and slotted external rotor internal stator TORUS type surface mounted permanent magnet (PM) machines (TORUS-NS and TORUS-S) have simple structures, relatively high efficiencies and low cost. These machines can be used for the applications that require high power and torque density, high efficiency and low noise with the use of neodymium-iron-boron (NdFeB) magnets providing relatively small overall size and weight. In this paper, sizing equations of the TORUS machines are derived using generalized sizing equations. The optimum machine design is illustrated by choosing the magnet pole-arc ratio and the skew angle of the rotor magnets. Using the optimum design data, field analysis of TORUS-NS and TORUS-S machines are investigated. Pulsating torque analyses including the cogging torque and the ripple torque are carried out using a 3D finite element analysis (FEA) software. Utilizing the techniques such as modifying the winding structure and skewing the rotor magnets, minimization of cogging torque and ripple torque for the TORUS-NS and TORUS-S machines are obtained and verified using 3D FEA. Finally a comparison of the TORUS topologies in terms of torque quality is illustrated in the paper.

Electromagnetic vibration and noise assessment for surface mounted PM machines

Analysis of electromagnetic vibration and acoustic noise assessment and methods to minimize resultant sound power level for low noise motor design is presented in this paper. The linear model of the exciting force wave is derived to evaluate the exciting force and to optimize the design of stator winding, rotor PM shape and rotor PM skew angle for minimization of sound power level for low noise motor design. Mode number and frequency of the exciting force wave, natural vibration frequency, maximum vibration velocity and maximum vibration displacement of main vibration source are introduced to evaluate machine vibration. Resultant sound power levels for the cylindrical sound wave and the plane sound wave models are introduced to analyze the acoustic noise assessment of both axial and radial flux PM machines respectively. Finally, electromagnetic vibration and acoustic noise assessment of both radial and axial flux surface mounted motor structures are completed and illustrated in the paper.

TORUS concept machines: pre-prototyping design assessment for two major topologies

Two different external-rotor-internal-stator TORUS type axial flux PM machines can be derived based on the direction of the flux. In the first type of the TORUS machine, magnet driven flux enters the stator and travels circumferentially along the stator core while, in the second type, the flux enters the stator and travels axially along the machine axis of rotation. The major differences between the two topologies are the direction of the magnet driven flux, the winding arrangement and the thickness of the stator yoke. In this paper, the sizing equations are derived for both types of TORUS machines. Based on the sizing analysis, optimum design is achieved for minimum ripple torque and maximum torque density. Furthermore, finite element analysis (FEA) of both TORUS structures are investigated to get an insight in 3D field distribution, flux directions and paths in different parts of the machines for different load conditions. Minimization of the cogging and ripple torque components of the TORUS concept machines are displayed using 3D FEA for the insight in pulsating torques, ripple torques and cogging torques. Finally the comparison of the TORUS topologies are made in terms of flux densities, cogging and ripple torques and the results are illustrated in the paper.

Optimum design and 3D finite element analysis of nonslotted and slotted internal rotor type axial flux PM disc machines

Axial flux internal rotor external stator surface mounted permanent magnet (AFIR) disc machines have simple structures, relatively high efficiencies and low cost. These machines can be used for the applications that require high power and torque density, high efficiency and low noise with the use of neodymium iron boron magnets. In this paper, sizing equations of the AFIR machines are derived using generalized sizing equations. Optimum machine design is illustrated by choosing the diameter ratio and the airgap flux density. Using the optimum design data, field analysis of the slotless and slotted AFIR machines are investigated. Pulsating torque analyses are carried out using a 3D finite element analysis (FEA) software. Minimization of cogging torque and ripple torque for both topologies is obtained using FEA utilizing the techniques such as modifying winding structure and skewing the rotor magnets. Finally the comparison of the two topologies in terms of torque quality is illustrated in the paper.

Analysis and evaluation of the transverse flux circumferential current machine

With the evolution of novel high power density machines, it becomes important to compare the power potential of such machines with vastly different topologies having a variety of different waveforms of back EMF and current. The approach of this paper is based on general-purpose sizing and power density equations, which will permit a comparison of the main dimensions and power of such machines. In this paper, the comparison method of machine power densities is extended to include the transverse flux circumferential current type permanent magnet (TFCCPM) machine, and furthermore to compare the power production capability between the TFCCPM machine and the well-known squirrel cage induction machine.

Design of an integrated motor/controller drive for an automotive water pump application

This paper addresses key technical issues in the design of an integrated motor/controller drive unit for which the electric motor, its electronic controller, and load (a pump impeller) are all combined into a single structural assembly. A cost-based trade-off study is described that includes five different types of brushless machines, leading to the selection of an interior PM synchronous machine as the preferred prime mover for this application. The physical configurations of the motor and the controller were designed in order to minimize weight and volume while maximizing their cooling effectiveness. Several key issues associated with the controller design are described, including the physical layout of key components, the development of the EMI filter to meet automotive specifications, and analysis of worst-case component temperature rises using finite-element thermal analysis.