Horia Balan

Polymer Electrolyte Fuel Cell System (PEFC) Performance Analysis

This paper presents a study of the fuel cell system performance operating at different pressure and temperature levels. A polymer electrolyte fuel cell (PEFC) is analyzed according with the possibility of using in transport applications. Therefore, it begin with the description of a parametric model of the fuel cell which has been developed using a combination between empirical and mathematics modeling techniques. This model enables to simulate fuel cells V-J curves in dependences with the stack temperature and the oxygen partial pressure. In addition, it can be used to study the influence of the gases management (pressure) on the fuel cell stack performances

Electromagnetic torque capabilities of axial-flux and radial-flux permanent-magnet machines

This paper aims to evaluate capabilities of axial-flux and radial-flux permanent-magnet machines. The comparison is done exclusively from an electromagnetic point of view. The electromagnetic design comparison of conventional radial- flux and axial-flux topologies is carried out in view of traction drive applications.

Flux-density space-harmonics minimization for an axial-flux permanent-magnet machine

The content of flux-density space-harmonics in axial-flux permanent-magnet machines (AFPMMs) is an important concern to the machine designer due to its impact on machine performances. In AFPMMs, the space-harmonics are related to the flux-density and the MMF distributions in the airgap, which are mainly determined by the PM excitation. This paper proposes two different approaches to study the flux density in the airgap. The finite-element and analytical methods are jointly developed in order to model and compare the flux density waveforms. Many optimization methods have been proposed in order to optimize the design of PM machines. In this paper, the authors investigate the optimal PM design in order to minimize the space-harmonics distribution using the sequential quadratic programming (SQP) optimization algorithm. By selecting the appropriate PM shape and size, it is possible to remove the undesirable harmonics. Using the SQP, the PM shape is optimized, and the harmonics content is notably reduced. The optimal solutions given by the FE model are then validated.

Frequency converter energetic performances analysis

The issue of non-conventional energy sources now is correlated with energy efficiency and clean energy. An application researched by the authors is vibration stress relieving, which consist in vibration of stress reliving piece with electromagnetic or electro-dynamic vibrator to determine frequencies of resonance. Technology is energy efficient and involves a single-phase inverter with variable frequencies, which generate a load current with minimal distortion factor in vibrator coil. The studied and experimental solution used by the authors is a classic inverter with LC turn-off circuit, who use sinusoidal modulation as command principle. This solution is compared from energetic point of view with un-modulated inverter and hybrid commutation inverter. For energy efficiency point of view power factor is interested. Active power P and total power S is analytic determined and is showed their dependence on quality factor Q. Paper emphasis dependence between angle of modulation a and power factor cosphi, for different values of resonance frequencies who making stress relieving.

Reliability modeling for an automatic level control system

Water resource availability is an important problem as water is basically used for everything we make. In a water distribution process the level and flow must be always controlled. Therefore, the parameters of the system must be known at any moment. This paper presents an automatic level control system which is analyzed in terms of reliability in order to present solutions to clarify how such systems could be designed as robust as possible.

Electromagnetic design and finite-element analysis of an axial-flux permanent-magnet machine

This paper approaches the electromagnetic design and finite-element analysis of an axial-flux permanent-magnet (AFPM) synchronous generator for small-scale wind turbines. The study is conducted to find a good-performance and cost-effective electric generator topology for micro-wind power application. The proposed double-sided two-stators-one-rotor AFPM synchronous generator with non-overlapping concentrated slotless-stator-winding and ironless PM-rotor disk could be the machine of choice in grid-connected or stand-alone small-scale wind energy conversion systems.

Series Resonance Technique for Short-Circuit Current Limiting Devices in DC Grids

The paper presents a by-pass solution used to limit the short-circuit current in the DC networks. The aim of the by-pass circuit consists in injecting a reverse current throughout the power switch, in order that switching achieves at low current value. The reverse current generation is obtained using a series resonant circuit, simulated in the paper in the Matlab-Simulink medium, the results of the simulation being compared to the experimental ones.

Fault current limiter in d.c. networks using thyristor by-pass circuits

This paper presents a method for limiting short-circuit current for d.c. systems. Classic methods for limiting short-circuit current are described as well as solid state devices used directly on current path and by-pass solutions. Thyristor and resonant circuit breaker version proposed by authors relieves current flow for every step during operation. Matlab simulation for these steps is useful for establish commutation periods for experimental model. This paper accentuate thyristor solid state breaker advantages comparative to other power solid state devices especially for high voltage.

Reduction of the Distortion Current Factor of the Current Drawn by the Electromagnetic Vibrators Supplied at Variable Frequency

The paper presents a possibility of supplying the electromagnetic vibrators with variable frequency voltage. Two types of modulated controls of the inverter’s commutation angle are presented. The theoretical analysis allows the study of the variable element influence on the distortion factor and of the harmonic content generated by the vibrator. The authors present an experimental validation of the presented theory, using the harmonic measurement of the distorted waveform. The harmonic response is useful in quantifying the performances of the harmonic filters to be introduced between the nonlinear consumer and the power grid and on the other hand the electromagnetic interference determined to other customers connected to the power grid.

Considerations on Electromagnetic Compatibility for Medical Devices

The paper deals with the electromagnetic compatible design of medical products, starting from the early stage of the design process (the prototype stage). This way of thinking is presented for the case of one kinetic therapy equipment. In the functional block diagram of the equipment are pointed out the main electromagnetic interference paths. The specific test setup and measurements in accordance with the European conducted immunity standards for electromagnetic compatibility are presented. Two kinds of measurement were performed: inter-system measurements (to the mains supply port) and intra-system measurements (to the printed circuit board and the internal cables). Several solutions for mitigating electromagnetic interference problems which greatly improved the electromagnetic immunity of the equipment are also depicted. The main conclusion which must be drawn from the present paper is that designing for electromagnetic compatibility is the most energy saving and cost effective policy.