Kay Hameyer

Comparison and design of different electrical machine types regarding their applicability in hybrid electrical vehicles

Because of high requirements in power, efficiency, installation space and weight, the design of electrical machines for hybrid electrical vehicles is a particular challenge. In order to make an informed decision, several machine types are pre-dimensioned by means of analytical formulae and compared with respect to their power density, efficiency and their applicability in hybrid vehicle concepts. The analytical pre-designs are evaluated by the finite element method (FEM). With regard to a parallel hybrid system with a very restricted installation space, a further study is performed on the permanent magnet excited synchronous machine, preferred for its highest power density and overall efficiency.

Solution strategies for transient, field-circuit coupled systems

Transient simulation time for field-circuit coupled models of realistic electromagnetic devices becomes unacceptably high. A magnetodynamic formulation is coupled to an electric circuit analysis, yielding a sparse, symmetric and indefinite matrix. The unknown circuit currents correspond to negative eigenvalues in the matrix spectrum. The Quasi-Minimal Residual method performs better than the Minimal Residual approach that is restricted to positive definite preconditioners. The positive definite variant is solved by the Conjugate Gradient method without explicitly building the dense coupled matrix. As an example, both approaches are applied to an induction motor.

Optimization of radial active magnetic bearings using the finite element technique and the differential evolution algorithm

An optimization of radial active magnetic bearings is presented in the paper. The radial bearing is numerically optimized, using differential evolution-a stochastic direct search algorithm. The nonlinear solution of the magnetic vector potential is determined, using the 2D finite element method. The force is calculated by Maxwells stress tensor method. The parameters of the optimized and nonoptimized bearing are compared. The force, the current gain, and the position stiffness are given as functions of the control current and rotor displacement.

Advanced Iron-Loss Estimation for Nonlinear Material Behavior

The aim of an optimal design of electrical machines requires the accurate prediction of iron losses for various operating points. For this purpose different iron-loss models have been proposed which intent to describe the loss inducing effects. The most used iron-loss prediction formulas are either physically based, but nevertheless only valid for linear material behavior at low frequencies and low magnetic flux densities, or grounded on a pure mathematical description of the material behavior, that is not more than interpolated measurements. This paper presents a modified loss equation with semi-physically based parameters as well as a first try to explain the nonlinear loss component.

Comparison of standards for determining efficiency of three phase induction motors

The paper describes a set of experiments and discusses their results for determining the efficiency of low voltage, three phase squirrel cage induction motors. The measured efficiency of an induction motor directly connected to the grid, strongly depends on the method used to evaluate the results and the standard according to which the measurements are performed. Different standards as IEEE 112 and IEC 32 are mentioned and their similarities and differences are discussed. The main discrepancies between the various standards is the way in which the values for the stray load losses are obtained at different load levels. A short description of the measurement setup is given and measurement results for motors of several manufacturers accounting for different standards are proposed. The results clearly demonstrate the necessity to handle the efficiency data given by the manufacturer with a lot of care.

A parametric finite element environment tuned for numerical optimization

Nowadays, numerical optimization in combination with finite element (FE) analysis plays an important role in the design of electromagnetic devices. To apply any kind of optimization algorithm, a parametric description of the FE problem is required and the optimization task must be formulated. Most optimization tasks described in the literature, feature either specially developed algorithms for a specific optimization task, or extensions to standard finite element packages. Here, a 2D parametric FE environment is presented, which is designed to be best suited for numerical optimization while maintaining its general applicability. Particular attention is paid to the symbolic description of the model, minimized computation time and the user friendly definition of the optimization task.

Manufacturing Tolerances: Estimation and Prediction of Cogging Torque Influenced by Magnetization Faults

Permanent magnet excited synchronous motor servo drives are increasingly employed in industrial applications. During mass production deviations from the ideal machine occur. Thereby, parasitic effects such as cogging torque and torque ripple are influenced in particular. For permanent magnet excited machines the magnets quality is important. There are many possible failure configurations requiring the study of their influence on the machines behavior. In this paper, an approach for the estimation of cogging torque considering magnetization faults is presented. This approach is applied to determine crucial configurations of permanent magnet faults. The intent is to evaluate the influence of the faulty magnetic materials with its asymmetries on the later produced machine. In the process, analytical and numerical methods are combined whereby finally a small computational effort with accurate results is achieved.

Study of Hybrid Excited Synchronous Alternators for Automotive Applications Using Coupled FE and Circuit Simulations

In this paper, an alternative arrangement to conventional Lundell automotive generators is examined. This geometry is characterized by hybrid excitation combining the high-energy density of permanent magnets and the controllability of commonly used electrical excitation. The rotor geometry of the alternator is optimized by means of finite element (FE) simulations and a prototype design is developed. The formulation for the transient solver is given and the coupling of the FE model with an external circuit is explained in detail. The accomplished studies, simulations, and geometry optimizations are presented. In a final step, the simulations are compared to prototype measurements and confronted with conventional alternator geometries.

Finite element analysis of steady state behavior of squirrel cage induction motors compared with measurements

The paper describes the steady-state analysis of squirrel cage induction motors using a two-dimensional finite element solution. Saturation is included using an iterative process combining both static and time-harmonic solutions. The motor end-effects are calculated using 2D and 3D finite elements including a lumped parameter approach during the solution of the time-harmonic problem. Both motors types, with closed and open rotor slots, are analysed. Different operating points for load, no-load and locked rotor situations are analysed and compared. The influence of the different end-effect parameters is analysed by including or neglecting them in the calculations. Good agreement with measurements are found for all operating conditions. The calculations are performed using a commercial FEA package.

Study and comparison of several permanent-magnet excited rotor types regarding their applicability in electric vehicles

Due to the limited available space and the high demands in power density and overall efficiency, the permanent magnet synchronous machine (PMSM) is the mainly applied machine type in parallel hybrid electric vehicles (HEV). This machine is used as well in many full electric vehicles (EV). In this work, several permanent-magnet excited rotor types are studied regarding their applicability in EVs and HEVs, and are compared in terms of among others: their maximum torque and power, power density, their efficiency map, field-weakening capability, overload capacity and torque ripple.