David Franck

Extension of a d-q model of a permanent magnet excited synchronous machine by including saturation, cross-coupling and slotting effects

For the description of a permanent magnet excited synchronous machine the idealized equations of common synchronous machines can be used omitting the damping windings and replacing the current excitation by a permanent flux. For a more accurate modeling, nonideal behavior like saturation, cross-coupling magnetization and slotting effects can be included. This is done by extending the common d-q equations by additional elements. This also includes the time dependent variations of the parameters causing additional induced voltages especially at high currents and speed. The elements of the extended equations are extracted from a finite element analysis of the device under test. The derivation of the equations and a simulation of a permanent magnet excited synchronous machine with the applied theory are presented.

Application of Sinusoidal Field Pole in a Permanent-Magnet Synchronous Machine to Improve the NVH Behavior Considering the MTPA and MTPV Operation Area

In this paper, various approaches to improve the noise, vibration, and harshness (NVH) behavior of a single-layer interior permanent-magnet synchronous machine (IPMSM) are evaluated. The studied machine is used in electric vehicles and has a maximum output power of 53.6 kW. The acoustic noise of the electrical machine is mainly generated due to vibration of the stator yoke, which is caused by the radial forces acting on the stators teeth. The radial force is directly correlated with the flux density in the air gap. Through modification of the outer frame of the rotor, the composition of the air-gap field, which consists of the fundamental wave and its harmonics, can be modified. The distribution of the radial force density on the surface of the stator teeth will be affected and the dominant order of the radial force can be reduced selectively, which will improve its acoustic behavior.

Static Electromagnetic Field Computation by Conformal Mapping in Permanent Magnet Synchronous Machines

In modern servo drives or electrical drives for positioning, torque pulsation, tangential forces and ripple torque are undesirable effects. These parasitic effects are due to the presence of higher time and space harmonics in the air gap flux density. This paper presents a time-effective method to compute the radial and tangential field components under load and no-load condition by conformal mapping in the frequency domain. The proposed method is applied to a surface mounted permanent magnet synchronous machine, and compared to numeric results obtained by nonlinear FEA. The analytical results obtained by the conformal mapping are shown to be in good agreement to the finite element simulations.

Active reduction of audible noise exciting radial force-density waves in induction motors

This paper presents an approach to the active reduction of radial force-density waves. Additional flux-density waves are generated by the injection of additional and particular low-power current harmonics. With these flux-density waves a force-density countershaft to an acoustic annoying radial force density wave is generated. In this contribution a mathematical model to estimate the amplitude, frequency and phase shift of the required current harmonic is presented. The prediction of the phase-shift is strongly dependent on saturation effects and on the interaction of the additionally imposed and existing flux-density waves. Therefore, a finite element (FE) experiment set is proposed to increase the accuracy of the analytically predicted phase angle. The active injection of force-density countershafts is performed, analyzed and evaluated. The assessment is performed based on FE simulations. The authors found that the injection of force-density countershafts is applicable for force-density waves with any circumferential oscillation modes and frequency in general. However, the consideration of oscillation modes is limited to r = 0, ±2p, ±3p and ±4p in order to keep the additional losses in the machine within an acceptable limit. The proposed approach is robust concerning the accuracy of the phase shift of the additionally imposed current harmonic.

Accounting for saturation in conformal mapping modeling of a permanent magnet synchronous machine

Purpose – In the electromagnetic field simulation of modern servo drives, the computation of higher time and space harmonics is essential to consider appearing torque pulsations, radial forces and ripple torques. The purpose of this paper is to propose a method to cover the effect of saturation on the armature flux density within conformal mapping (CM) by an finite element (FE) re‐parameterization.Design/methodology/approach – Field computation by CM techniques is a time‐effective method to compute the radial and tangential field components, but it generally neglects the effect of saturation.Findings – This paper presents a method to re‐parameterize the CM approach by single FE computations so as to consider saturation in the model over a wide operation range of the electrical drive.Practical implications – The proposed method is applied to a surface permanent magnet synchronous machine, and compared to numerical results obtained by finite element analysis (FEA).Originality/value – The paper shows that an...

Design of an electrical motor with wide speed range for the in-wheel drive in a heavy duty off-road vehicle

The electrification of the mobile machinery is often discussed. For agricultural tractors an electric drive can be an alternative to commonly used hydrostatic-mechanical power split drives. When compared to the hydrostatic drive, the electric motor with an efficiency above 90% offers advantages. For a meaningful comparison the complete drive train (generator, gearbox, power supply, electric motor) has to be considered. Generally, a particularly limited space is available for the integration of an electric drive. This requires a compact design of the electric motor. Therefore, a permanent magnet synchronous motor is the best candidate, due to its high power density and high efficiency. A particular challenge when designing an electric motor is a special requirement on the driving cycle of the agricultural tractor. The electric motor has to provide a high torque for the working operation off-road and a high maximal motor speed for the transportation operation to move the vehicle on road. For this research a shiftable transmission gear is omitted. The design process of the electric motor with special characteristics is described. The challenge of the motor design for a wide speed range is the main subject of this paper.

Influences of material degradation due to laser cutting on the operating behaviour of PMSM using a continuous local material model

During manufacturing of electrical machines, shape giving production steps such as punching and cutting introduce plastic deformations and residual stress to the soft magnetic material. As a result the magnetic properties of the material decreases and locally both, static and dynamic hysteresis losses increase in the vicinity of the cut surfaces. For consideration of local permeability deteriorations, different models have been published. These are capable to describe the changing local magnetisation and loss behaviour. Current approaches subdivide the magnetic core into slices of different magnetic properties, thereby discretising the continuous deterioration. This paper analyses the effects of material degradation due to cutting on the performance and machine parameters of a Permanent Magnet Synchronous Machine (PMSM) using a continuous material model for efficient numerical modelling of the local magnetisation behaviour. By replacing inefficient sliced models, the continuous model is independent of the discretisation and converges in case of coarse meshes to the sliced model. Influences on the machine behaviour are studied in terms of local flux density distributions, iron losses, efficiency, torque and inductances on the operating map and an exemplary working point.

Towards low audible noise drives for FEV applications

This paper presents the required steps for the multiphysics acoustic simulation of electrical machines to evaluate its noise behaviour. The proposed scheme is of particular interest for the design and development of electrical drives for full electric vehicles (FEV), because it allows predicting the acoustic characteristic before building a prototype. This numerical approach starts with the electromagnetic force-wave simulation. The computation by a structure dynamic model determines the deformation of the mechanical structure due to the force-waves. The final step of the simulation approach consists of the computation of the excited acoustic radiation. Here, particular attention is paid to the structural-dynamic model. Modelling of microstructures, such as the laminated iron core or insulated coils, is memory and computational expensive. A systematic material homogenisation technique, based on experimentaland numerical modal analyses, yields a higher accuracy at lower computational costs when compared to standard numerical approaches. The presented multiphysics simulation is validated by measurements. The proposed methods are presented by means of a realistic and technically relevant case study.

Continuous Local Material Model for Cut Edge Effects in Soft Magnetic Materials

Shape-giving production steps in the manufacturing of electrical machines often introduce plastic deformation and residual stress into the soft magnetic material, thus decreasing the magnetic quality and locally increasing both the static and dynamic hysteresis losses near the cut edges. Different models have been published, aiming to describe the changing local magnetization and loss behavior. Current approaches often consider permeability deteriorations by subdividing the soft magnetic material into the slices of different material properties. Three cut edge models are discussed here, where two describe the changed local polarization and the third estimates the resulting global iron losses. This paper presents a continuous material model for an efficient numerical model of the local magnetization. By replacing effortful sliced models, the continuous model is independent of the discretization and converges in the case of coarse meshes to the sliced model.

On the effect of material processing: microstructural and magnetic properties of electrical steel sheets

This paper presents both the effect of cutting on the material behavior of a typical used NGO electrical steel grade M230-30A as well as a study of the effect of annealing temperature after cold rolling on microstructure and magnetic properties beginning with an industrial hot rolled 2.4 wt.% Silicon steel of 2.0mm thickness. Modifications in the local mechanical properties due to the cutting process are investigated in detail. A quantitative analysis of the impact of material degradation for non-oriented electrical steels applied in traction drives is presented. In order to consider the large speed range of drives in automotive applications and the presence of higher harmonics, this analysis is conducted for a wide range of frequencies and magnetic polarizations. Nanoindentation is used to analyze the effect of strain from cutting on the hardness near the surface. A major conclusion is that it is indispensable to take into account influences due to material processing on magnetic materials properties during the design process of electrical machines.