Drago Dolinar

Evaluation of saturation and cross-magnetization effects in interior permanent-magnet synchronous motor

The paper presents the evaluation of saturation and cross-magnetization effects in interior permanent magnet synchronous motor (IPMSM) over the entire range of direct and quadrature axis excitation. The conventional two-axis machine model is modified in order to include the influence of saturation and cross-coupling effects on the variation of self and cross-coupling inductances in the direct and the quadrature axis. The two-axis machine model parameters are evaluated by experiments performed on a IPMSM using a controlled voltage source inverter and are compared with parameters values evaluated by the finite element method. The evaluation of two-axis machine model parameters reveals significant saturation and cross-magnetization effects in both axes, especially in the flux-weakening regime.

Parameter Identification of the Jiles–Atherton Hysteresis Model Using Differential Evolution

In this paper, parameters of the Jiles-Atherton (J-A) hysteresis model are identified using a stochastic search algorithm called differential evolution (DE). The J-A hysteresis models parameters are identified by DE in such a way, that best possible agreement is obtained between the measured and model calculated hysteresis loops. This agreement is furthermore increased by improving the J-A hysteresis model. The improvement is achieved by replacing a constant pinning parameter in the J-A hysteresis model with a variable one. Here, the variable pinning parameter is written as a function of a magnetic field. By DE identified parameters are used in the J-A hysteresis model, which is included in the dynamic model of a single-phase transformer. The effectiveness of the improved J-A hysteresis model and parameters identification approach is verified with experiments and simulations.

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.

Line-Starting Three- and Single-Phase Interior Permanent Magnet Synchronous Motors—Direct Comparison to Induction Motors

The performance comparison of three- and single-phase line-start interior permanent magnet synchronous motors (LSIPMSMs) and induction motors (IMs) with equal squirrel-cage design and symmetric four-pole stator windings is presented. The finite element method was employed in analysis of steady-state synchronous performance of LSIPMSMs. A magnetically linear lumped parameter model was employed in analysis of line-starting performance of LSIPMSMs, where the electrical and also the mechanical subsystems were considered. The procedure which was used for the LSIPMSM design was validated by comparison of calculation and measurement results. The performance of three- and single-phase LSIPMSMs and IMs with equal squirrel-cage design was directly compared and evaluated, thus emphasizing impacts of the permanent magnet breaking torque and reluctance breaking torque on the LSIPMSM performance in the asynchronous operation region.

Evaluation of experimental methods for determining the magnetically nonlinear characteristics of electromagnetic devices

The properties of magnetic material are normally described by the permeability tensor, while the magnetically nonlinear properties of electromagnetic devices (EMDs) can be described by the current-dependent characteristics of flux linkages. This paper presents and evaluates different experimental methods appropriate for determining the magnetically nonlinear characteristics of EMDs. The tested device is supplied by a controlled voltage source. Sinusoidal voltages, sinusoidal voltages with offset, and stepwise changing voltages are applied. Current-dependent characteristics of flux linkages are determined from the measured voltages and currents, either by numerical integration or by Fourier analysis and calculation of impedances.

Identification of linear synchronous reluctance motor parameters

The paper deals with the identification of parameters of a two-axis linear synchronous reluctance motor (LSRM) dynamic model. The model parameters are identified by experiments performed on an LSRM using a controlled voltage source inverter. The current dependent direct- and quadrature axis inductances are identified by experiments and calculated by the finite element method. The calculated inductances are compared with the inductances identified by experiments. As the translation range of the tested LSRM is limited, the proposed parameter identification procedure has been verified indirectly through the comparison of simulation and experimental results in the case of kinematic control. Compared are the reference and the actual position, speed, current and voltage trajectories obtained by experiment and by simulation. The agreement of the results is good.This paper deals with experimental methods for the identification of linear synchronous reluctance motor (LSRM) parameters. A magnetically nonlinear two-axis dynamic LSRM model is derived. This model accounts for the effects of slotting, saturation, cross-saturation, and the end effects. The parameters of the obtained model are not constant. They are given by the characteristics of the flux linkages, thrust, and friction force depending on the mover position and the direct (d) and quadrature (q) axis currents. These characteristics are determined experimentally by a controlled voltage-source inverter employing closed-loop current control in the d-q reference frame. The proposed model, experimental methods, and determined characteristics are confirmed through a comparison between the measured and calculated results. Two tests are performed: a test at the locked mover, and kinematic control at low speed. The effects of cross saturation under dynamic operating conditions and the effects of slotting can be clearly seen in the measured and calculated results.

Impact of magnetic nonlinearities and cross-coupling effects on properties of radial active magnetic bearings

The impact of magnetic nonlinearities and cross-coupling effects on the properties of the discussed radial active magnetic bearings (AMBs) is evaluated in the entire operating range. The characteristics of flux linkages and radial force are all determined by finite element computation, while the current and position dependent partial derivatives of the flux linkages are calculated by analytical derivations of the continuous approximation functions. Calculated current and position-dependent partial derivatives, as well as the radial force characteristics are incorporated into the proposed dynamic AMB model. The results presented show that the magnetic nonlinearities and cross-coupling effects can change the electromotive forces and the radial force considerably. These disturbing effects have been determined and can be incorporated into the real-time realization of nonlinear control in order to achieve cross-coupling compensations.

Determining Magnetically Nonlinear Characteristics of Transformers and Iron Core Inductors by Differential Evolution

This paper deals with the differential evolution (DE)-based method for determining the magnetically nonlinear iron core characteristics of transformers and iron core inductors. The unknown iron core characteristic, approximated by the sum of exponential functions, is included in a dynamic model of the tested device. The approximation function parameters are determined by DE. The optimization objective is the best possible agreement between the measured and the dynamic model calculated currents in the time and frequency domains. Using the measured inrush currents and corresponding voltages, the magnetically nonlinear characteristic can be determined over a broad operational range. The inclusion of iron core characteristic, as determined by the proposed method, in the transformer dynamic model gives very good agreement between the measured and calculated currents in both transient and steady states.

A Three-Phase Core-Type Transformer Iron Core Model With Included Magnetic Cross Saturation

The behavior of a power transformer (PT) depends considerably on the properties of the magnetically nonlinear iron core. This paper deals with the modeling of a three-phase, three-limb power transformer laminated iron core. The proposed iron core model is given by the corresponding partial derivatives of measured flux linkage characteristics. The magnetically nonlinear characteristics of flux linkages are determined by the controlled simultaneous magnetic excitation of all three limbs. This enables determination of magnetic cross couplings between different limbs, due to the saturation. The obtained iron core model integrated in the circuit model of PT is compared to the classical saturated iron core model without cross couplings, by analyzing the transient behavior of an unsymmetrically excited transformer. The numerical results obtained by the proposed iron core model agree with the measured results much better than those obtained by the existing nonlinear iron core model known from literature

Calculation of the linear induction motor model parameters using finite elements

The paper presents the use of the finite element (FE) method for determining the parameters of a two-axis model of a three-phase linear induction motor. The model parameters are obtained from the FE field solutions. The saturation of the motor is taken into account in calculation of the flux distribution by using a static nonlinear vector potential solution. The linear time harmonic vector potential field solution is used for the determination of inductances. All inductances are determined at the nominal value of the magnetizing current. The parameters of the model obtained by the described identification procedure are compared with the parameters calculated in the conventional way and the agreement of results is quite good.