Oliver Winter

A Detailed Heat and Fluid Flow Analysis of an Internal Permanent Magnet Synchronous Machine by Means of Computational Fluid Dynamics

This paper presents a comprehensive computational fluid dynamics (CFD) model of a radial flux permanent magnet synchronous machine with interior magnets. In the CFD model, the water jacket cooling and a simplified model of the topology of the distributed stator winding are considered. The heat sources of the CFD model are determined from a finite-element analysis of the machine. The numerically determined temperature distributions of the machine are compared with measurement results from sensors located both in the stator and rotor. The particular focus of this paper is the analysis of the temperatures and the heat flow in the air gap and from the stator winding heads and the rotor to the inner air. Different operating conditions and two particular rotor designs with different inner air flow configurations are investigated. The potential of improving the thermal utilization of a rotor design with fan blades attached to the mounting plates of the rotor is shown.

Modeling demagnetization effects in permanent magnet synchronous machines

This paper presents a permanent magnet model which takes temperature dependencies and demagnetization effects into account. The proposed model is integrated into a magnetic fundamental wave machine model using the modeling language Modelica. For different rotor types permanent magnet models are developed. The simulation results of the Modelica are compared with measurement results. Additionally, the fundamental wave model is compared to a finite element analysis in order to assess the applicability of the proposed model.

Augmented Temperature Degrading Effect of Rare Earth Magnets Arranged in Segmented Halbach Arrays

If rare earth magnets are arranged in a Halbach array, flux concentration occurs at one side of the array. This principle can be utilized in electric machines to augment the air-gap flux density or even to omit flux carrying iron parts. Highly utilized electric machines are operated at elevated temperatures requiring an appropriate selection of the material. However, the uncommon magnet orientation required in a Halbach array entails an augmented temperature degrading effect in the magnets. The effect is studied in three test cases with linear arrangements of Halbach arrays by means of 2-D and 3-D Finite Element Analysis and is validated through measurements.

Heat and fluid flow analysis of an internal permanent magnet synchronous machine by means of computational fluid dynamics

This paper presents a comprehensive computational fluid (CFD) model of a radial flux permanent magnet synchronous machine with interior magnets. In the CFD model the water jacket cooling and a simplified model of the topology of the distributed stator winding are considered. The heat sources of the CFD model are determined from a finite element analysis of the machine. The numerically determined temperature distributions of the machine are compared with measurement results from sensors located both in the stator and rotor. The particular focus of this paper is the analysis of the temperatures and the heat flow in the air gap and from the stator winding head and the rotor to the inner air.

Ironless in-wheel hub motor design by using multi-domain finite element analyses

In this paper, a lightweight ironless axial flux permanent magnet drive concept is presented. The in-wheel hub motor has a high torque to weight ratio and achieves a high efficiency, which extends the operation range of battery powered vehicles. The steps from preliminary design to manufacturing of the components are described. The paper includes Finite Element Analyses in different physical domains.

Influences of iron loss coefficients estimation on the prediction of iron losses for variable speed motors

This paper addresses the influence of the estimation of hysteresis, eddy current and excess loss coefficients on the prediction of the overall iron losses in traction motors. Two standard iron loss models (according to Bertotti and Jordan) are presented and it is examined how the determination of the corresponding loss coefficients is effecting the iron loss calculation for variable speeds. It is shown that the accuracy of the iron loss calculation does not mainly depend on the number of iron loss terms in the model but rather depends on the computation of the corresponding coefficients. To reduce the uncertainty of the iron loss calculation, common curve fitting methods have to be used carefully. Provided that constant coefficients and exponents of the loss component terms are used, the resulting coefficients estimation by means of curve fitting methods depends on the considered frequency range of the measured losses given by the electrical steel manufacturer. Three different FEM analysis tools are used to compare the iron loss calculations for a simplified electrical machine model and a permanent magnet assisted synchronous reluctance machine (PMaSyRM) model.

Design and loss assessment of air cored axial flux permanent magnet machines

This paper focuses on different calculation methods of Joule losses in a winding and Halbach magnet arrays for air cored axial flux motors. The classical approach (I) for winding losses results in eddy current losses without proximity effect but with induced currents for the passing magnetic field. The second method (II) derives the frequency dependent resistance including skin and proximity effects to calculate the winding losses due to higher current harmonics generated by pulse width modulation (PWM) excitation. The calculation of eddy currents (III) induced by higher harmonics in the magnet array is used to evaluate two different assembly strategies concerning the joule losses within the magnets. Based on the results from these three methods, final design decisions were made. A full-scale prototype in-wheel hub motor was manufactured and measured to assess the chosen design.

Simulating the change of magnetic properties of electrical steel sheets due to punching

Electrical machines are, especially in combination with modern power electronics, the driving horse in industry, traction and automotive applications. So there is a lot of research ongoing in the fields of new or improved topologies, better performance and increased efficiency. Latter one requires a better knowledge of the loss mechanisms in the machine in order to find solutions to reduce them. The iron losses, resulting from a varying magnetization in the ferromagnetic lamination sheets, are the most complex loss component in an electrical machine. One factor influencing the iron losses significantly is the manufacturing process. Among the different production steps, punching of the machines lamination can be considered to have a very high impact on the magnetic properties. If there is knowledge on how these properties depend on the mechanical and the process parameters there is considerable potential to optimize the process or the machine design to increase the machines efficiency. This paper will present simulation models trying to forecast the losses of punched lamination sheets. Therefore, the punching process was simulated with Finite-Element software. The resulting distribution of mechanical stress and plastic strain was incorporated in the Jiles-Atherton model to calculate the magnetic hysteresis of the lamination sheet. A comparison with measurements will show the applicability of the methodology.

Estimating the magnetic characteristics of a salient pole synchronous machine using ampere turns distribution method

This paper presents a simple yet effective method to determine the flux density-magnetic field intensity (B-H) characteristics of the magnetic material used in a salient pole synchronous machine (SPSM). This is achieved by distributing the magnetic field intensity, H, in the different parts of SPSM using 2D Finite Element (FE) simulations and theoretical calculations. The distribution is based on the open circuit characteristics (OCC) of an actual SPSM. The method avoids complicated optimization methods and can be used in conjunction with commercial finite element (FE) softwares, where implementing such optimization techniques may be difficult. The method requires only an initial estimate of the B-H characteristics using a default core material provided by the software. The procedure will be useful for simulating SPSMs or other electric machines whose magnetic material properties are approximately known but has changed with long usage and aging. Theoretical calculations complimented with simulation and experimental results prove the effectiveness of this new method.

Determination of the Magnetic Characteristics (B–H) of Material Used in a Laboratory-Rated Salient Pole Synchronous Machine Using a Novel Ampere Turns Distribution Technique

This paper presents a simple method to determine the approximate flux density-magnetic field intensity ( B-H) characteristics of a material used in a laboratory-sized salient pole synchronous machine (SPSM). The objective is achieved by distributing the magnetic field intensity H in the different parts of an SPSM using finite-element (FE) simulations and theoretical calculations based on the open circuit characteristics of an actual SPSM. This method requires only an initial estimate of the B -H characteristics of core material. The advantage of the method proposed is it can be used to estimate the magnetic properties of material that might have changed with long usage and aging. Theoretical calculations complimented with FE simulation and comprehensive experimental results prove the effectiveness of this new method.