This paper presents a two-dimensional analytical analysis and dimensioning procedure of a novel low-leakage linear transverse-flux machine (TFM). The two-dimensionalanalytical models approximate the complex three-dimensional fluxes of the TFM. Theanalysis is based upon how the different airgap permeances and the non-linear iron reluctances in the different machine sections vary, as the translator is traversed through the airgap. The reluctance networks for the magnetomotive force (MMF) of the magnets and for the current dependent armature-MMF are solved simultaneously. A 5-kW proof-of-concept machine is dimensioned and its performance predicted using the described procedure. The different performance defining parameters are derived as continuous functions of the translator position. The dependence of the machine power factor and the force capability upon the current loading, which is quite interesting when analysing TFMs, is also investigated.

2.

Arshad, Waqas M.

et al.

KTH, Skolan för elektro- och systemteknik (EES).

Thelin, Peter

KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.

Bäckström, T.

Sadarangani, Chandur

KTH, Tidigare Institutioner, Elektrotekniska system.

This paper investigates the use of transverse-flux machines (TFMs) in a free-piston generator, an integration of a combustion engine and a linear electrical machine. For hybrid vehicles (the intended application), this integrated device has benefits in efficiency, emissions, reliability, etc. Conventional TFMs are dimensioned and their shortcomings illustrated. Several surface-mounted TFM designs are suggested. These designs, initially believed to be promising, are later discovered to be. poor during the three-dimensional finite-element method (3-D FEM) analysis. These designs suffered from a large axial pole-to-pole armature-flux leakage in the stator. This problem is solved in the proposed buried-magnets TFM variants, for which patents have been filed as well. A 5-kW proof-of-concept prototype of one such design is dimensioned that allowed the near fulfilment of 3-D FEM verifiable system demands. One phase. of this dimensioned three-phase prototype is built. Measurements on this,prototype showed that the use of short pole lengths in the machine had led to manufacturing defects. Nevertheless, the electromagnetic viability of the design could still be approximately verified.

The complex three-dimensional fluxes in a newly introduced high-performance transverse-flux electrical machine are investigated. The magnet-flux, the armature-flux and the combined-flux in the machine are studied as a function of mover position. Separate non-linear reluctance networks for the magnets- and current- magneto-motive forces are developed and solved simultaneously in an iterative manner. The airgap is modelled by defining two/three-dimensional varying permeances. The iron is represented with three different non-linear reluctances. The analytical models are fine tuned and verified by employing a detailed three-dimensional finite element analysis. The role these fluxes play in the determination of the machine's performance is also described. Lastly, it is shown how these fluxes help explain the machines' measured performance when unexpected manufacturing defects occurred.

The aim of this paper is to evaluate different concentrated fractional pitch winding designs in comparison to a distributed full pitch winding design with one slot per pole per phase as a reference. The rotor design is fixed and the permanent magnets are surface mounted, i.e. the rotor has negligible magnetic saliency. The studied parameters are power capability considering inverter capacity, field-weakening performance, torque ripple (including cogging), iron losses, winding losses and thermal behaviour. The results of the machine performance comparisons are based on a comprehensive use of finite element analysis tools. Measurement results from tests on a laboratory prototype are used to define heat coefficients.

In the design of a compact inverter-fed buried permanent magnet synchronous motor, the high-frequency losses of the sparse rotor cage - which are difficult to predict - were assumed to be small. To investigate these ohmic high-frequency losses of the rotor cage, fixed-speed time-stepping 2D-FEM calculations have been carried out. The losses due to only the magnets, magnets and sinusoidal currents, high-frequency currents etc., and the actual currents are presented. The actual current wave-forms were obtained from measurements on the manufactured prototype motor.

7. Zheng, P.

et al.

Nordlund, Erik

KTH, Skolan för elektro- och systemteknik (EES).

Thelin, Peter

KTH, Skolan för elektro- och systemteknik (EES).

Sadarangani, Chandur

KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.

The 4-quadrant energy transducer (4QT) is a solution to realize both the torque and speed control of the internal combustion engine (ICE) for hybrid electric vehicles. Since the base frequency of the prototype 4QT is much higher than the industrial one, the effect of eddy current on winding current distribution is considered in this paper. A two-dimensional (2-D) eddy-current FEM model is established and used for analysis. Current density and strand current distribution are given. It is pointed out that owing to the effect of eddy current, the conductor currents are unevenly distributed within the strands of the same turn. According to the 2-D FEM analysis, when the uneven current distribution is considered, the average rms turn current is increased by 1.05 times for the stator and 1.65 times for the inner rotor, and the copper loss is increased by 1.1 times for the stator and 3.16 times for the inner rotor. Since the inner rotor slots are much deeper than the stator slots, the inner rotor current distribution is more uneven than the stator. It means that for high-frequency deep slot machine the eddy current effect should be considered seriously. Because of the increased current and copper loss, more ventilation will be needed for the 4QT, especially for the inner rotor. The average torques of stator machine and double rotor machine meet the requirements, and the torque ripples are small owing to the skewed slots.

An inductance determination method that can be based on both experiments and calculations is discussed in this paper. The inductances of a four-quadrant transducer (4QT) prototype machine were measured and calculated with the two-dimensional time-stepping finite-element method (FEM), and the measured and calculated results are in good agreement. It is found that the d- and q-axis inductances are different, and the inductances obtained from the phase and line voltage are also different for both the two machines of the 4QT prototype machine. Analysis shows that the differences are caused by the saliency and d-axis saturation. Although there is little saliency for the double rotor machine (DRM), the two kinds of the inductance differences of the DRM are more serious than that of the stator machine (SM). This is because of the higher level of the d-axis saturation of the DRM. The inductances obtained from the phase voltage at very low frequency are recommended as final results for both experiments and calculations.