E Esin Ilhan

Analytical Hybrid Model for Flux Switching Permanent Magnet Machines

With the emergence of energy related issues in the automotive sector, there is a tendency to find new efficient solutions to replace existing electrical machinery. One promising candidate is the flux switching permanent magnet machine (FSPMM). Due to its challenging structure and nonlinear characteristic, in the investigation of the machine, generally finite element method (FEM), and rarely the magnetic equivalent circuit (MEC), are implemented. The following paper introduces an alternative analytical modeling technique by means of a hybrid model, which combines the advantages of the MEC and the Fourier analysis.

Modeling of Flux Switching Permanent Magnet Machines With Fourier Analysis

For applications demanding a high torque density and high speed capability, the flux switching permanent magnet machine is an excellent candidate. However, the double salient structure and nonlinear behavior increases the challenge to model the magnetic field distribution and torque output. To date, only the magnetic equivalent circuit (MEC) is employed to model the magnetic field in an analytical manner. However, the MEC method suffers from a coarse discretization and the need for a relative complex adjustment when rotor movement or a parametric sweep is considered. Therefore this paper discusses an alternative technique based on the harmonic or Fourier model which solves these difficulties.

Tooth contour method implementation for the flux-switching PM machines

Flux-switching machines are attracting interest among researchers over the last decade due to the increased importance of energy efficient systems. Among this class of machines, the rotary flux-switching PM machines (FSPM) with high power density are mostly analyzed by magnetic equivalent circuit (MEC) and finite element methods (FEM). In addition to those analysis techniques, this paper introduces the implementation of the tooth contour method (TCM) for the first time for a rotary FSPM. During the modeling phase, many points are revealed which are essential for the electromagnetic behavior of this unconventional machine.

Relative Permeability in a 3D Analytical Surface Charge Model of Permanent Magnets

The analytical surface charge model is used to calculate the magnetic field of magnets in 3D in an unbounded domain. The method combines high accuracy with a short calculation time. However, in the classical method the relative permeability of the magnet is assumed to be equal to air. This introduces an error in the resulting magnetic field strength. In this paper the permeability of the magnet is taken into account in the form of a redistribution of magnetic surface charge. As such, an exact solution for the magnetic field at low relative permeability is obtained. The interaction force between two magnets is calculated using the newly obtained expressions for the magnetic field and compared with FEM and measurements.

Spatial Discretization Methods for Air Gap Permeance Calculations in Double Salient Traction Motors

Weight limitations in electric/hybrid cars demand the highest possible power-to-weight ratio from the traction motor, as in double salient permanent magnet (PM) machines. Their high flux densities in the air gap result in nonlinear analytical models, which need to be time optimized. The incorporated reluctance networks are sensitive to the correctness of air gap permeances. Conventionally, in these networks, air gap permeances are calculated by approximating flux paths; however, it is time inefficient. For an improved simulation time, spatial discretization techniques are presented to calculate air gap permeances in double salient PM machines. The spatial techniques discussed here cover the tooth contour method and Schwarz-Christoffel (SC) mapping as semidiscrete methods, which are used to discretize only the air gap region. Their results are verified by the spatial discrete method and finite element method, which discretizes the whole machine geometry. For consistency in this paper, all methods are explained on a three-phase 12/10 flux-switching PM motor. Obtained air gap permeances show a very good agreement with only 0.8% difference. Further on, machine characteristics such as phase flux linkage and cogging torque are also compared to show the impact of the modeling techniques. The total machine simulation time is improved by 20% using the SC method. Although methods are explained particularly for double salient PM machines, formulas are generalizable for other machine types as well.

Fast torque estimation of in‐wheel parallel flux switching machines for hybrid trucks

Recently, parallel flux switching machines (PFSM) have come forward as a promising candidate for hybrid and electrical truck applications due to their high power density. Torque calculations, i.e cogging and electromagnetic, are important features of these machines. However, they require a finite element model (FEM) with a long simulation time, especially for transient analyses. This paper explains how the simulation time can be minimized by employing a torque superposition principle.

Design considerations of flux-switching machines with permanent magnet or DC excitation

Flux-switching permanent magnet machines and dc-excited flux-switching machines share the advantages of robust rotor structure and high torque density. In this paper, comparative analysis is performed on the two types of machines, in terms of flux-linkage, thermal condition, torque density, and field-weakening capability.

Conformal mapping: Schwarz-Christoffel method for flux-switching PM machines

PurposeFlux-switching permanent magnet (FSPM) machines are double salient machines with a high energy density suitable for e-mobility. For a fast design process, machine specialists need easy-to-use motor models. For the FSPM model, analytical methods cost high efforts to create and to improve them. Numerical methods such as the finite element method (FEM) have been extensively studied in the literature with little emphasis given to their alternatives.MethodsThis research shows the implementation of the Schwarz-Christoffel (SC) mapping for the FSPM. With this numerical method, the double salient motor geometry is transformed into a simpler geometry to reduce the model complexity. For the electromagnetic analysis, SC mapping is implemented both as a stand-alone method and as an integrated method with the tooth contour method and the orthogonal field diagram method.ResultsFindings are presented in a comparative analysis for all created models including the finite element method. Results show a very good agreement among the presented models.ConclusionsThe results obtained in this paper show that SC mapping is a good alternative to the FEM. With the provided step-by-step explanation on how to implement SC mapping, the method can be expanded to other electrical machine classes.

Control of DC-excited flux switching machines for traction applications

Electrical traction motors face challenging torque-speed requirements. DC-excited flux switching machine (FSM) offers inherently a good torque capability along with an effective controllability thanks to its DC field windings. These machines have been evaluated mainly over their performance with little consideration on their control. This paper proposes a control strategy, applied on a 3-phase 6/5 DC-excited FSM for traction applications. To obtain the non-linear magnetic behavior of the machine, 2D finite element method (FEM) simulations are performed. The controller regulates the DC field current before reaching base speed to minimize the iron and copper losses. Due to the high armature reaction of the motor the speed range is extended by limiting both the field and armature currents as a function of the speed and inverter supply voltage. Torque control of the machine is performed throughout its complete speed range.

Transient thermal analysis of flux switching PM machines

Flux switching permanent magnet (FSPM) machines bring together the merits of switched reluctance and PM synchronous motors. FSPM employs armature windings and PMs together in the stator region, therefore the proximity of the windings PMs makes a thermal model mandatory. In literature, thermal modeling of the FSPM is not addressed extensively compared to its electromagnetic modeling. With this aim, first a steady-state TEC model is created for a 3-phase 12/10 FSPM. Additionally, conformal mapping, in particular Schwarz-Christoffel, is used to increase the accuracy of the TEC model. Using Laplace transformation, the steady-state model is extended to a transient thermal model. Results are compared and validated by the finite element method.