DIMENSIONAREA SISTEMULUI DE PROPULSIE AL UNUI VEHICUL ELECTRIC. STUDIU DE CAZ

This paper aims to present to readers concrete mathematical models, transposed into simulation schemes, to calculate the forces acting on a car at its interaction with the road and the atmosphere, to properly size the electric motor and batteries of an electric car. For the calculation of these forces, a table with predefined values ​​such as vehicle mass, rolling resistance coefficient, gear ratio, wheel radius, was used throughout the work. In the second section of the paper, the values ​​of the resistance forces that oppose the movement of the vehicle and the traction force necessary to overcome these resistive forces were determined. The mathematical calculation model was compiled in Matlab and the graphs in figures 3-9 were obtained.

THE ANALYSIS OF THE THREE-PHASE INDUCTION MOTOR WITH DEEP ROTOR BARS THROUGH NUMERICAL SIMULATIONS UTILIZING A MODIFIED MATHEMATICAL MODEL

The three-phase induction machine mathematical model presented in the paper, is adequate for applying to the deep rotor bars case. The rotor resistance R’r(r), respectively its leakage inductivity L’r(r), depend upon the rotor currents’ frequency fr because of the skin effect. Following the previous considerations, one developed slip dependent analytical expressions of the rotor circuit resistance R’r(s), respectively rotor circuit leakage reactance L’r (s). A modified space phasor based mathematical model of the deep bar induction motor is tested through simulations to assess the motor’s characteristics. The results are in accordance with the literature.

EVALUAREA SOLICITĂRILOR TERMICE ȘI A DURATEI DE VIAȚĂ A TRANSFORMATOARELOR DE DISTRIBUȚIE AFLATE ÎN REGIM PERIODIC NESINUSOIDAL

Electrical transformers are some of the most important equipment in the entire electricity distribution chain. Their operation with optimal values of the parameters (electrical, thermal and mechanical) ensures the continuous supply of consumers. The modern electrical loads of power distribution transformers are often nonlinear and generate several power quality problems, especially the distortion of the waveform of the current that flows through the windings of the transformer. This generates additional stresses (electrical and thermal) of the various components of the transformer (originally designed to operate in pure sinusoidal mode) which can cause abnormal (faulty) operation of the transformer and ultimately reducing its life (estimated by the manufacturer for permanent sinusoidal regime). In order to prevent or diminish the negative effects of the nonsinusoidal regime on the transformer, a deliberate limitation (reduction) of its maximum load is performed. The procedure is known as transformer derating. Its main aim is to establish the most appropriate declassification factors (denomination), resulting from the correlation of the nominal and constructive data of the transformer with the power quality parameters, measured in its secondary part (usually, these are the current distortion level and the corresponding spectrum harmonic). This paper analyzes qualitatively and quantitatively these aspects and proposes a downgrading procedure for in-service transformers which it illustrates in a case study.

EXPERIMENTAL RESULTS ON THE RADIO REMOTE CONTROL AND REMOTE MONITORING OF THE ANTI-HAIL MISSILE LAUNCHPADS

The paper presents a technical solution for monitoring and operating the anti-hail missile launchpadsusingan internet-connected wireless remote control, which operates in the 433 MHz ISM frequency band. A small size experimental model of the real launchpad wasdevised and built, in order to test the local operation of the remote control and its over-the-internet monitoring function. When designing the experimental model, attention was given to preserving the characteristics of the actual launchpad,such that after testing the technical solutions of the remote control on the model, they could be implemented on the real launchpad with minimal modifications.This experimental modelcan also be used for staff training during the active off-season. The proposed technical solution presents an example of how the electrical machine, seen as an element of execution, is included in the concept of the Internet of Things.

UNITATE DE CONTROL TELEMATICĂ PENTRU SISTEME INTELIGENTE DE CONDUCERE

"The telematics control unit system uses the functionalities of the A.D.A.S, E.C.M and A.B.S systems already existing on vehicles involving the hardware, software and mechanical components offered by them. The system is a service that provides the user with traffic safety and prior information on impediments to streamline the route. This paper presents how it is proposed that this system process the data and transmit it to a server that will then transmit this information to an interactive map. The telematics control unit system uses the functionalities of the systems A.D.A.S, E.C.M and A.B.S already existing on vehicles involving the hardware, software and mechanical components offered by them. The system is a service that provides the user with traffic safety and prior information on impediments to streamline the route. This paper presents how it is proposed that this system process the data and transmit it to a server that will later transmit this information to an interactive map."

ASPECTE CALITATIVE ȘI CANTITATIVE ALE FENOMENUL DE FEROREZONANȚĂ ÎN INSTALAȚIILE ELECTRICE DE JOASĂ TENSIUNE

The phenomenon of ferroresonance is generated by the interaction between nonlinear magnetic devices and capacitive elements in an electrical installation in which losses are reduced and which are constantly supplied by at least one energy source. Feroresonance is manifested by the appearance of overvoltages and overcurrents in the installation with strongly distorted waveforms. Also, the phenomenon is accompanied by other disturbances of the quality of electricity (voltage fluctuations, asymmetries, noise, etc.), which propagate in the network affecting the proper functioning of the entire installation. In addition, unlike linear resonance, ferroresonance allows the manifestation of several stable states (modes) for the same parameters of the network, these being imposed by the initial conditions in the installation and the moment of occurrence of the phenomenon. Thus, the vulnerability to low resonance of a low voltage installation has become an indicator of electricity quality. This paper presents a procedure for calculating and investigating this phenomenon based on the analysis of numerical solutions of systems of differential equations (nonlinear and non-autonomous), which models the transient phenomena that initiate the appearance of ferroresonance (usually switching processes). Also, modern means of investigation are used (3D visualizations in the phase plan or Poincaré diagrams), imposed by the difficulty of the quantitative analysis both in dynamic regime and in stationary regime of ferroresonance. In addition, methods and procedures are proposed to mitigate the effects of the ferroresonance phenomenon on equipment or network elements in electrical distribution installations.

NUMERICAL SIMULATION OF THERMAL CONDITION OF A LOW CURRENT ELECTRIC CONTACT

Electrical contacts may include various sub-systems or wiring harness connected via detachable connectors which depend on physical contacts for the electrical connectivity. Electrical contacts range from high, medium to low current depending on their usage. However, in the real-life condition, electrical contacts characteristics, especially at the interface, undergoes a gradual change which can be due to corrosion, temperature variation, aging, strained harnesses, discontinuities induced by vibration etc. These changes introduce additional parasitic circuits in the system. Moreover, in some cases where the contact resistance increases due to electrical loses, the local temperature may increase, thereby accelerating contact degradation. This paper presents a numerical analysis on the variation of temperature of a simple low current contact model having a thin oxide film layer at the interface which serves as the ageing factor using finite element method (FEM).

ELECTROMOBILITY TOPICS ENTERING A NEW DECADE

During the last ten years the electric vehicles became more and more part of the daily mobility. Supported by different policies, but also by the technology advance, the electromobility is far to be an achieved topic and enters a new decade. The hybrid solutions continue to offer an alternative using the combustion engines. Latest researches and developments on fuel cells push to an alternative future, based on hydrogen. The electric batteries, as energy storage on vehicle, remain the most important way to conduct EV to the roads, with regular improvements. In fact, all these technologies are developing solutions to provide and control the energy for an electric motor. The classic solution using one engine and a kinematic chain to distribute the mechanical power to the wheels is completed by the possibility to integrate not only one, but more electric motors in the same vehicle.

CALCULUL CÂMPULUI ELECTRIC ASOCIAT UNUI CUPLOR INDUCTIV DESTINAT TRANSFERULUI DE PUTERE WIRELESS

"Contactless or wireless power transmission has become a widespread disruptive technology. Although known for more than 100 years, it is the result of the unprecedented development of microelectronics and power electronics in recent decades. Numerous technical solutions for near-field energy transmission at different power and frequency levels are currently established: capacitive electric field transmission (CPT), inductive magnetic field transmission (IPT), multi-coil transmission and simultaneous transmission via electric field and magnetic field as a combination of the first two. The materialization of the contactless transmission is achieved in theory and practice through different types of contactless coupling circuits, generically called ""contactless couplers"". The inductive coupler can be considered as an electrical transformer in air or with open magnetic circuit in which the primary (Tx) and the secondary winding (Rx) can occupy different positions from each other depending on the application [1]. It is considered a representative element for WPT (Wireless Power Transfer) systems currently used from transferred powers of several watts to tens or hundreds of kilo-watts. To increase the transfer efficiency, the coupler works at high frequencies, of the order of kHz or MHz and in some cases has planar windings, of different shapes, made of litz wire and usually has magnetic flux concentrators [2]. Any inductive coupler is integrated into a complex transmission system, consisting of many other components [3]. In addition to the electromagnetic calculation widely presented in other works, open magnetic circuit construction produces electric and magnetic scattering fields that have a negative effect on both electrical and electronic equipment in the vicinity and on human health if the exposure exceeds certain thresholds. These thresholds are indicated by international standards and requirements [4-5] achieved by applying the precautionary principle [6] so that they can be reviewed periodically and are not mandatory unless they are taken over in national law. In this paper we analyze by the finite element method, in approximate 2D, the electric field produced by an inductive coupler in various simplified construction variants and calculate certain related quantities of practical importance such as: electric field distribution in the field of calculation, electric field strength in the vicinity of the inductive coupler, equipotential lines, reactive power, equivalent capacities."

ANALIZA UNUI ECRAN MAGNETIC POZIțIONAT ÎN SPAȚIUL DINTRE ÎNFĂȘURĂRILE UNUI TRANSFORMATOR MONOFAZAT, DE MICĂ PUTERE

"This paper aims to analyze the impact of using a thin magnetic shield placed in the space between the primary and secondary winding of a simplified, low power, single-phase transformer used in energy harvesting applications that demand power transformers not only in the energy conditioning stage but also in the energy harvesting stage. By using magnetic shields, the saturation of the ferromagnetic core and, in some particular cases, the destruction of electronic devices is avoided. For this purpose two scenarios are studied: one which doesn't take into account the magnetic shield, as it considers only the air space between the primary and secondary windings, respectively, and the second case study which considers a magnetic screen placed in the centre of the air space domain. The size of the air space domain, d, is varied as the secondary winding distance itself from the primary one until it reaches the core. The number of turns in the primary and secondary winding is equal, N1 = N2 = 300 turns. By moving the secondary winding away from the primary winding, the variation of the distance d between the coils is achieved, thus keeping the same cross-section of the secondary winding. The thickness of the magnetic shield is chosen arbitrarily, as thin as possible, with a dimension of 400 µm. The idealy, 1:1, simplified, low-power, single-phase transformer powered by a harmonic voltage supply at V1 = 20 V and at a frequency, f = 50 Hz, with load resistance of Rs = 100 Ω, is analyzed in a time-dependent study and its computational domain is taken from literature [4]. Different materials can be used for realizing this magnetic shieling, even copper and aluminum, but in this paper a magnetic sheet metal material is considered because of its small, almost nonexistent electrical conductivity. Our goal is to analyze the effect of magnetic shielding on the saturation of the ferromagnetic core, and the reactance and resistance values of the primary and secondary winding, respectively, for different dimensions of the air space, d. For comparison purposes, the second model, the one in which we have the magnetic sheet metal, an analysis is performed in the permanent harmonic regime, in addition to the one performed in the dynamic one."