Dae-Joon You

Characteristic Analysis on Axial Flux Permanent Magnet Synchronous Generator Considering Wind Turbine Characteristics According to Wind Speed for Small-Scale Power Application

To use a permanent magnet (PM) synchronous generator to wind power generation systems, the wind turbine characteristics according to wind speed should be considered in the design stage and performance evaluation. Using the wind turbine characteristics provided by a manufacturer, we predict the performance of a wind power generator that uses an axial flux PM by analyzing the electromagnetic field characteristics. To avoid the long analysis time required by the three-dimensional finite element method because of the structural features of axial flux PM machines, an alternative analytical approach is presented, and its results are validated experimentally. In addition, we present an AC-DC-DC converter that is connected to the experimental setup for back-to-back tests in order to obtain constant output regardless of wind speed variations.

Electromagnetic Performance Analysis of Wind Power Generator With Outer Permanent Magnet Rotor Based on Turbine Characteristics Variation Over Nominal Wind Speed

In this paper, we investigate the electromagnetic performance of wind power generators with outer permanent magnet rotors on the bases of variations in the turbine characteristics over nominal wind speeds by employing various proposed analytical techniques. We have employed an electromagnetic analytical method for calculating electrical parameters such as back EMF constant, synchronous inductance, and phase resistance on the basis of the magnetic field distribution calculated in previous studies. Moreover, curve fitting and finite element methods have been used for core losses analysis, while the d-q model employing the coordinate transformation theorem has been used for analyzing generation performances. To validate our techniques, we compared the performance results obtained using our analytical methods with those obtained by experimental setups. In addition, we propose optimized wind turbine characteristics for our model from the analysis results of electromagnetic performances obtained by considering three types of turbine characteristics.

Design and Experimental Evaluation of Synchronous Machine Without Iron Loss Using Double-Sided Halbach Magnetized PM Rotor in High Power FESS

The rotational loss is one of the most important problems in high-power flywheel energy storage system (FESS) which supplies the electrical energy from the mechanical rotation energy. In our FESS with PM synchronous motor/generator (PMSM/G) and non-contacting system, the rotational loss is mainly generated in the laminated iron stator when PM rotor mounted on the flywheel is rotated. Therefore, this paper presents design and evaluation of a PMSM/G model composed of double-sided Halbach magnetized PM rotor and ironless 3-phase winding stator to minimize speed reduction of the flywheel. For one such motor structure we give analytical formulae for its magnetic field and back-electromotive force in a uniform way via the magnetic vector potential. As a result of experiment, dynamic performance of a manufactured double-sided PMSM/G is evaluated by comparison with those of the slotless PMSM/G in the idling mode. The result shows that the presented PMSM/G can be applicable to the high-power FESS.

Design and Characteristic Analysis on the Short-Stator Linear Synchronous Motor for High-Speed Maglev Propulsion

The design and characteristic analysis on the linear synchronous motor (LSM) for high-speed maglev propulsion is discussed. We describe the techniques for the design, analysis, construction, and experiment of a prototype propulsion system with short-stator LSM. On the basis of a 2-D analytical field analysis, this paper predicts the magnetic field due to dc excitation and three-phase winding current, the back-EMF, and the electromagnetic torque characteristics. The results are validated extensively by comparison with finite-element analysis and experiment. The propulsion performance was tested by using a high-speed rotary type test wheel with linear peripheral speed up to 283 km/h.

Dynamic Performance Estimation of High-Power FESS Using the Operating Torque of a PM Synchronous Motor/Generator

In our high-power flywheel energy storage system, the heavy and large flywheel is rotated by the electromagnetic torque of a permanent-magnet (PM) synchronous motor (PMSM) and, in case of a breakdown of electric current, this motor used as a generator supplies electric energy to the various electric utilities using mechanical rotation energy of the flywheel. Thus, the dynamic performance of the flywheel is related to the electromagnetic torque for the motoring and generating power of the PMSM/G. Moreover, in the idling mode without generating loads, speed reduction of the flywheel is mainly caused by drag torque generated in the slotless iron-cored stator of this PM machine. In this paper, the operating torque, defined as the electromagnetic torque and drag toque, is estimated from the magnetic-field analysis by the PM rotor with diametrical magnetization. Also, the dynamic performance of the flywheel, according to the driving mode, is simulated from dynamic modeling of the PMSM/G with the operating torque and verified by the experiment.

Operating Torque Estimation of High-Speed Slotless Brushless DC Machine Considering Power Loss

Torque is very essential for performance evaluation of electric machines because it is directly connected with power loss for dynamic characteristics. To evaluate dynamic performance, torque with harmonic component according to time is introduced. Particularly, eddy current loss is significantly increased at high speed, so it is difficult to express the dynamic characteristic without reflection about losses. Therefore, in this paper, rotor eddy current loss wave is derived by fast Fourier transform which uses the phase current wave obtained from finite element analysis according to two conditions: one has rotor eddy current loss, the other does not. The core loss is deduced by a modified Steinmetz equation and additional losses are considered from an experiment. Those losses are worked as drag torque which is inverse force to performance of a machine. The operating torque estimated from the difference between drag torque and electric torque closely reflects the dynamic characteristics.

Dynamic Performance of Tubular Linear Actuator With Halbach Array and Mechanical Spring Driven by PWM Inverter

This paper deals with dynamic performance of the tubular linear actuator with mechanical spring driven by a pulse wide modulation (PWM) inverter for bidirectional drive. An equivalent electrical circuit was obtained for the tubular linear actuator with the mechanical component represented by a mass-spring system with motional impedance. By analyzing this circuit the variations in power factor, current, active and reactive power vs. frequency was investigated as well as the resonant circuit frequency. Experimental results for dynamic characteristics such as current and stoke are presented for various values of frequency including resonant frequency. In particular, discussion for experimental results at the resonant frequency is presented fully.

Comparative Study of Electromagnetic Performance of High-Speed Synchronous Motors With Rare-Earth and Ferrite Permanent Magnets

The rare-earth permanent magnet (PM) is commonly used to improve the performance of high-speed electrical machines to compensate for their high production costs, while it is very likely that the demand for high-speed machines will increase in the near future as markets for new technologies continue to grow. However, a high-speed machine is required to have high performance and low manufacturing cost, because mass production is needed for these applications. Therefore, in this paper, a high-speed machine using a ferrite PM was designed to significantly decrease the manufacturing costs. To examine the performance of the high-speed machine suggested in this paper, the performance of a high-speed model using a ferrite PM is compared with that of a SmCo PM model. A high-speed machine with a specification of 3 kW and 30 000 r/min is designed and manufactured. The designed model is analyzed using the finite-element method. Finally, the no-load back electromotive force in each model is examined through a back-to-back experiment.

Analysis on operational power and eddy current losses for applying coreless double-sided permanent magnet synchronous motor/generator to high-power flywheel energy storage system

This paper deals with analytical approach of operational power defined as load power and rotor loss represented as eddy current loss for applying a permanent magnet (PM) synchronous motor/generator to the high-power flywheel energy storage system. The used model is composed of a double-sided Halbach magnetized PM rotor and coreless three-phase winding stator. For one such motor/generator structure, we provide the magnetic field and eddy current with space and time harmonics via magnetic vector potential in two-dimensional (2D) polar coordinate system. From these, the operational power is estimated by backelectromotive force according to the PM rotor speed, and the rotor loss is also calculated from Poynting theorem.

The influence of mechanical spring on the dynamic performance of a moving-magnet linear actuator with cylindrical Halbach array

An influence of mechanical spring on the dynamic performance of a moving-magnet linear actuator with cylindrical Halbach array is described. On the basis of two dimensional (2-d) analytical solutions and experimental results, this paper estimates control parameters such as thrust constant, back-emf constant, inductance and resistance. And then, the voltage and the motion equation, which provide dynamic simulation algorithm, of a moving-magnet linear actuator are established. In particular, by expressing mechanical components as the motional impedance from the motion equation, this paper investigates not only the variation of the motional impedance according to system parameters but also the variation of power dissipated in the linear actuator with/without spring vs. frequency. Finally, the simulations and experiments for dynamic characteristics such as current and displacement of the moving-magnet linear actuator with/without spring are presented for various values of frequency.