Cristian Farcas

Modeling and simulation of supercapacitors

In this paper we present some models for supercapacitors. The supercapacitors are used more and more in high level industries such as: traction systems, automotive industry, aerospace industry, telecommunications etc. Understanding supercapacitors operation mode is necessary so we can be able to determine the applications which require these components, and to be able to choose between supercapacitors and other energy storage devices. In this paper were used some models for the implementation of supercapacitors, and the simulations made in Orcad 9.2 to determine their operation, are in time and frequency domain. Also, the models were implemented in Simulink 7.5 and the simulation results prove the models accuracy. Two test measurements on the ECOND Pscap350 supercapacitor were realized and using the measurement data, two methods to compute the parameters are presented.

An improvement on empirical modelling of photovoltaic cells

The photovoltaic (PV) cells convert solar radiation directly into electricity. An operating point of a photovoltaic module will move by the variation of the solar radiation, cell temperature, cell surface and values of the load connected to the system. In this paper four models for photovoltaic cells were analyzed, and two improved empirical models were implemented. The empirical models were developed using Mathcad and were validated by comparison of the obtained characteristics with the ones given by the manufacturers of the PV panels.

Switch mode power supply used for medical applications — Packaging and thermal analysis

Placed, in the structure of the paper, in the center of the general PCB integration process, the Intermediate Data Format (IDF) is a specification designed to provide a neutral representation for exchanging printed circuit assembly (PCA) data among mechanical design (MCAD), PCA layout (ECAD), and physical design analysis (MCAE) applications. The paper presents a combined analysis — starting from electrical design, then the 3D model, thermal and mechanical approach of the PCB Layout for a power supply unit for medical applications.

Packaging and thermal analysis of power electronics modules

The Intermediate Data Format (IDF) is a specification designed to provide a neutral representation for exchanging printed circuit assembly (PCA) data among mechanical design (MCAD), PCA layout (ECAD), and physical design analysis (MCAE) applications. Powerful analysis software, like Ansys, Maxwell, Semcad, Altium Designer or SolidWorks – CircuitWorks, can import the idf files and use the model for electromagnetic or thermal analysis. The information can also be used for a mechanical approach point of view. The paper will present a combined analysis – starting from electrical design, then the 3D model, thermal and mechanical approach of the PCB Layout for a relative humidity and temperature controller as a case study.

A Novel Topology Based on Forward Converter with Passive Power Factor Correction

A new topology of the forward converter with passive power factor correction is proposed. The degree of novelty consists by adding the third winding of the forward converter in the valley fill circuit. In this way, a forward converter with high power factor and lower THD can be obtained. This is a good solution for low and medium power application. The paper describes the proposed circuit. An important advantage of this circuit is that the maximum voltage on power transistor will be reduced from 2 UI to about 1.5 UI.

Digital Control of a Two Phase Motor

In this paper a two-phase motor control with an AtMega8 microcontroller is presented. The energy efficiency of motor-driven products is increased by adding variable speed control using a microcontroller. In this way, the motor can be operated in a wide range of speed and the implemented power saving procedures increases energy efficiency of motor-driven product. The motor is controlled by two Sinus Weighted PWM signals, displaced 90 degree in phase, with variable frequency and amplitude. To achieve greater efficiency the motor is started at low speed and accelerated to the operational speed. Also, at the first start the real power is measured for each operating speed, allowing in this way to find out the most energy efficient speed. The motor will be operated at this speed as much as possible.

Weekly electronic pills dispenser with circular containers

This paper proposes the improvement of the process of health recovery by using a programmable medication dispenser. We designed and realized an electronic pills dispenser with seven circular containers. The dispenser is realized around PIC18F458 microcontroller which controls all the function of the dispenser. Using a keyboard and an LCD, the user can easily set the hour when the pills will be supplied on a plate. When the time for medication is arrived, a dose of medication is released and an audio alarm is generated. If the patient does not take the dose prescribed by the doctor, an SMS is sent to a phone number.

Comparison between fixed and solar oriented PV modules' energy production using a simplified PSIM model

This paper presents a simplified Powersim (PSIM) model for simulating and estimating the power losses due to the change in the relative position of the sun to a fixed south oriented solar panel. The proposed equation used for describing the difference between the sun-tracking system and the fixed system is validated by testing a solar panel guidance system based on data provided by Stellarium software. The results obtained when using a fixed, a single-axis and a dual-axis tracking system are compared for different energy test reports. For example, in summer time (Cluj-Napoca), when using Stellarium indications, if only the azimuth is respected, the energy production can be increased by almost 31%, and by about 35% if the elevation is respected as well. This is compared to a fixed south oriented solar panel tilted at 45 degrees.

A new forward based converter with power factor correction

The paper presents a forward converter with power factor correction. The novelty of the paper consists in a combination between a forward converter and a valley fill circuit. The auxiliary winding of forward converter is included in valley fill converter. The new converter has a high power factor. The paper will present the design, simulations and experimental results of the proposed circuit. Another important advantage of the proposed circuit is a reduced stress of the power transistor.

Thermal modeling and analysis of a power device heat sinks

This paper presents a study about thermal behavior of heat sink - power device assembly. The power device (power transistor, triac, thyristor etc) and the heat sink were modeled in SolidWorks. These models have been used in simulations. We take into consideration different power devices packages, different heat sinks and different thermally conductive pastes. A thermal analysis has been performed by position of heat sink on PCB. In our study, we have taken into consideration the influence of the holes from heat sink in heat dissipations. The results of simulations and experimental measurements realized with a temperature data logger are presented in the paper.