Aurel-Ionut Chirila

On the model of a Hybrid Step Motor

The paper presents numerical simulation results and experimental data used for modeling a hybrid step motor (HSM). Two different HSM models have been developed starting from available technical data of a HSM (2-phase, bipolar, frame size 56.4 mm). One of the models is adequate for analyzing the HSM response to different control strategies, while the second one can be used for performing an electromagnetic field analysis.

A new five-level voltage-source-inverter using unidirectional switching cells and a coupled-inductor

Recently, a new five-level (5L) inverter has been developed. It is named 5L-USC1 and was based on the use of four 2L unidirectional switching cells (USC) and a coupled-inductor (CI) for each phase. This topology was derived from three-level Neutral-Point-Clamped (3L-NPC) inverter. In the paper a new 5L inverter based on basic USC is presented. It is named 5L-USC3 and is based on the use of six 2L unidirectional switching cells and a coupled-inductor for each phase. The proposed topology is derived from 3L-Active-NPC inverter by separation the bidirectional switching cells into two USC groups. The new 5L topology has more degrees of freedom in comparison with the recent 5L-USC1 inverter. As a result, the apparent switching frequency of the output voltage is four times the switching frequency of power devices and so, the current ripple is reduced by half. The apparent switching frequency in each inductor winding is twice the switching frequency of the power devices and thus, the magnetically coupled-inductor windings are considerably reduced.

PLC controlled elevator drive system

This paper presents a control method for an advanced electrical drive system for transportation, namely an elevator. For cost efficiency the control is performed with the simplest appropriate PLC. Thus, the software code was wisely developed to be fast and small size. Starting from an educational platform, which models a two floor elevator using a DC electrical drive, different sensors types and a PLC, the development of the actual driving sequences and PLC program, written using ladder diagram language, is detailed. In order to account for various normal operation and malfunctioning scenarios, some testing techniques are presented as well as their implemented into the PLCs program. Thereby, the paper has also an instructive aspect for engineers working in the automation field.

CAD for three phase ONAN cooling system transformers

This paper presents a Computer-Aided Design method for a three phase power transformer using MATLAB programming environment. The considered transformer is Oil Natural Air Natural cooling system type. During the designing by changing the value of just one single variable implies to recalculate everything. Such operation is time consuming but this drawback can be overcome by fully automating the design procedure, for example using MATLAB. The developed program is written in script format so that it can be easily modified to fit the imposed parameters of the transformer. The designing algorithm of the transformer has been optimized. Thus, it has ten steps with nine validation checkpoints. It may also be used as an educational model. The validations are implemented into the code and are required because there is no sure-fire method for designing a transformer from the first attempt. During the design it is necessary to change various values. Thus, only when all nine verifications are satisfied one may conclude that the transformer is well designed.

Development of a DC test network for monitoring power transfer

One solution for increasing the use of renewables is to find new strategies to allow distributed energy resources (DER) connection with the existing power system. A solution which allows a flexible integration of dispersed generation (DG) into energy networks is the use of DC at the user layer. One reason for choosing nowadays the DC technology for electrical energy distribution is the trend in the low voltage (LV) load characteristics. For most of the equipment, high performance is required and is ITC labeled - i.e. hosting a DC power source accommodating an inverter due to the present AC-distribution. Anticipating the further extensive use of low-power, DC-based, intelligent devices, one can avoid losses in energy transfer by using a DC layer within the distribution networks, at least where the energy is produced in a DC-form. DC grids in buildings are expected to be one of the main applications and challenges in the future. First promising applications are built around low power domestic loads and on concepts related to dispersed generation and their efficient integration into intelligent networks. In this paper the development of a DC test network, including measurement and communication, is presented.

Educational platform for working with programmable logic controllers

The restructuring and the reorganization of the educational teaching system has comprehended not only the academic teaching curriculum and management system but also the teaching methods. Educational platforms and virtual laboratories are increasingly becoming a key component during the teaching process especially for technical teaching. Although the existence of virtual laboratories and e-learning platforms can be very useful tools for electrical engineering in particular they will never replace real laboratories. The main reason is that using real educational platforms the students have the opportunity to become familiar with the basic principles and real elements of a particular area. Moreover, they can develop various complex applications and test their behavior. In the end, the main objective is that the present students - future engineers should be able to both operate real world systems and implement designed solutions that are likewise the teaching platforms. In this vein it is proposed a platform based on the programmable logic controllers (PLC) technology that has not been done so far. It is designed to be open enabling to add new modules and features. While the considered platform is based on a specific brand of PLC it can be very easily adapted without major technical issues to other brands.

Petri net versus Ladder Diagram for controlling a process automation

Industrial automation is constantly expanding, and, regarding their control more and more solutions are presently developing on the market. These include older methods like Petri nets (1966), and standardized languages, which are commonly used in the field of programmable logic controllers (PLCs). The paper presents the Ladder Diagram programming language, that is one of the standardized languages, and one of the most widely used for industrial automation systems. In these circumstances, it is useful to make a comparison between the two methods, drawing out the advantages and the disadvantages of each solution separately. Petri nets benefit from the existence of a highly developed mathematical support and high flexibility in analyzing all elements that can influence the conduct of an event, which is a major advantage. On the other hand, the Ladder Diagram language, which corresponds to the standard IEC 61131, is easy to use and implement, regardless of the hardware structure used by the manufacturer. Also, this method allows both ON-line and OFF-line simulations of the automation process operation. Finally, an educational platform is also presented.

Numerical modeling of the electric linear generators based on the sea waves energy

The paper presents the design, the calculus and a numerical simulation of the magnetic field, the electromotive force and the electromagnetic forces for a direct driven permanent magnet linear generator buoy, used to generate electric energy based on the sea wavepsilas energy. The magnetic field is computed using finite element method applied on a 3D model of the generator.

Fan cowl's orifices type analysis of fan-cooled induction motors

The paper aims to study which type of orifice type (round or square) is more efficient for an induction motor fan cowl, in order to obtain an increased air flow rate. The analysis begins from an already existing fan cowl (with square orifices) and it is shown that it is possible to improve the air flow rate. The chosen efficiency parameter is the flow coefficient, which is calculated using computational fluid dynamics means.

Noise analysis for no load operating power transformers

In this paper is presented a statistical analysis of the sound power emitted by power transformers. The power of the analyzed transformers within this analysis is greater than 6 MVA in no-load operation when the cooling system is turned off. Using this statistical approach the complex multiphysics problem of estimating the transformer sound power is greatly simplified.