Maarten J. Kamper

Optimal design of a coreless stator axial flux permanent-magnet generator

This paper describes a hybrid method for calculating the performance of a coreless stator axial flux permanent-magnet (AFPM) generator. The method uses a combination of finite-element analysis and theoretical analysis. The method is then incorporated into a multidimensional optimization procedure to optimally design a large power coreless stator AFPM generator. The measured performance of the manufactured prototype compares favorably with the predicted results. The design approach can be applied successfully to optimize the design of the coreless stator AFPM machine.

Anisotropy Comparison of Reluctance and PM Synchronous Machines for Position Sensorless Control Using HF Carrier Injection

Position sensorless control of reluctance and permanent magnet synchronous machines at zero and low speed is possible using HF voltage injection and proper demodulation. The so-called saliency position, which is tracked by the HF sensorless scheme, is different from the actual rotor position: the difference contains both offset and rotor-position-varying components, which may be explained by carefully considering the HF behavior of the machine and the effect that fundamental excitation and rotor position have upon it. This paper gives insight into the HF behavior of synchronous machines and serves as a practical guide for implementation of stable and robust position estimation at zero and low speed.

Analysis and Performance of Axial Flux Permanent-Magnet Machine With Air-Cored Nonoverlapping Concentrated Stator Windings

In this paper, the performance of air-cored (ironless) stator axial flux permanent magnet machines with different types of concentrated-coil nonoverlapping windings is evaluated. The evaluation is based on theoretical analysis and is confirmed by finite-element analysis and measurements. It is shown that concentrated-coil winding machines can have a similar performance as that of normal overlapping winding machines using less copper.

Direct finite element design optimisation of the cageless reluctance synchronous machine

The finite element analysis method is used directly in optimisation algorithms to optimise in multidimensions the design of the cageless reluctance synchronous machine. Two optimisation methods are evaluated to minimise or maximise the function value. These are the direction set method of Powell and the quasi-Newton algorithm. Both methods proved to be successful, with some advantages and disadvantages. Using these methods at a power level below 10 kW, results are given of structures of the reluctance synchronous machine which have been optimised according to specific criteria. Calculated and measured results show that the maximum torque optimum designed reluctance synchronous machine has the advantages of high power density and high efficiency.

Calculation of eddy current loss in axial field permanent-magnet machine with coreless stator

This paper presents a hybrid method for the calculation of eddy current loss in coreless stator axial field permanent-magnet (AFPM) machines. The method combines the use of two-dimensional finite element (FE) field analysis and the closed-form eddy loss formula. To account for three-dimensional field effects in an AFPM machine, a multilayer and multislice modeling technique has been devised. Experimental tests are carried out to validate the method. It is shown that the proposed method predicts the eddy current losses of a coreless stator AFPM machine with high accuracy.

Effect of stator chording and rotor skewing on performance of reluctance synchronous machine

Low torque ripple in electrical machines is generally required to reduce acoustic noise and mechanical resonance vibration. To design for low torque ripple, however, affects the average torque and the power rating of the machine. In this paper, the effect of stator winding chording and rotor skewing on the average torque, power factor, and torque ripple of the normal laminated, internal flux barrier rotor reluctance synchronous machine is investigated. The two-dimensional finite-element time-step method together with the basic machine equations are used in the analysis. It is shown that to design, in general, for low torque ripple and minimal effect on torque rating of the reluctance synchronous machine, full-pitch stator windings must be used, the rotor must be skewed by a stator slot pitch, and a low number of stator slots must be avoided.

Design Aspects of a Novel Topology Air-Cored Permanent Magnet Linear Generator for Direct Drive Wave Energy Converters

Direct drive wave energy converters are attractive due to the elimination of intermediate mechanical power conversion stages. Longitudinal flux (LF) linear generators with iron-cored stators have so far been dominant in experimental direct drive WECs, but suffer from high bearing loads and unwanted end effects. A novel linear air-cored topology is presented in this paper which eliminates most of the end effects associated with LF iron-cored machines as well as the attraction forces between iron-cored stators and magnet translators. The attraction forces between the opposing sides of the translators of double-sided air-cored machines are also ideally eliminated. An analytical model and an exhaustive optimization procedure for finding the minimum active mass subject to certain performance specifications are developed for the novel topology. Finite element analysis is used to verify and further analyze the model. First test results from a 1 kW experimental machine correspond well with designed values and confirm the feasibility of implementing the novel topology on a small scale.

Performance of a hybrid electric vehicle using reluctance synchronous machine technology

The performance of a parallel hybrid electric vehicle with a small reluctance synchronous machine drive is presented. The machine is current angle controlled for maximum torque per ampere or minimum kVA. This ensures that the machine is operated reasonable close to optimal efficiency for all loads. The calculated and measured performance results of the reluctance synchronous machine drive and the electric vehicle are given. The 28 kW peak reluctance synchronous machine is used to drive the back wheels of a small delivery-vehicle through a differential. The conventional petrol-engine propelled front drive is kept standard. Simulation and measured results show that with the small RSM drive generating a peak torque of 150 Nm, the 1480 kg vehicle accelerates from 0-60 km/h in 19 seconds. The maximum range of the HEV on a single battery charge is measured as 90 km at 60 km/h.

Development of a thermofluid model for Axial field permanent-magnet Machines

A thermofluid model combining a lumped parameter heat transfer model and an air-flow model of a typical axial-field permanent-magnet (AFPM) machine is developed. The accuracy and consistency of the derived model are assessed by comparing the calculated flow rate and temperature values of a prototype machine with the measured ones. The developed thermofluid model is shown to perform thermal calculations with reasonable accuracy.

IPM Traction Machine With Single Layer Non-Overlapping Concentrated Windings

In this paper, an interior permanent-magnet traction drive machine with single layer non-overlapping concentrated stator winding is analyzed. In the single layer winding design, the number of stator slots and a winding factor are specifically considered. Moreover, the effect of varying the coil pitch on the winding factor and torque pulsations is investigated. A new calculation method is proposed, whereby the constant torque and field-weakening speed characteristics of the machine drive can be predicted using torque and flux linkage functions. The measured and predicted field-weakening performance of a 150-kW direct traction drive machine is presented.