Operation of traction drive and auxiliary power supply converters installed onboard modern vehicles causes increased content of line harmonics and interharmonic components in the line current. ...Passive techniques for filtration of low frequency interference line currents appeared to be insufficient, but are combined with active mitigation techniques. The paper describes and suggests active suppression methods based on proper design of the grid interface of the power converter and its corresponding control system. Interference currents, including those induced by the operation of onboard power converters can significantly influence the correct operation of telecommunication, train control systems and other railway signaling infrastructure along the tracks, having direct impact to the safety of the railway transport. Therefore, suppression of low-frequency interference line currents requires careful implementation of active/passive methods. For purpose of quality evaluation of performances of the grid interface of the traction drive converters and its corresponding control system in particular, a series of tests for assessment of the line current frequency spectrum, resulting from the operation of the converter in typical exploitation conditions, were performed. Tests were performed in laboratory conditions and on the vehicle, with satisfactory results.
Široka primjena pretvarača glavnih i pomoćnih pogona, na suvremenim željezničkim vozilima, uzrokuje pojavu povećanog sadržaja neželjenih viših harmonika te međuharmonika u strujama pojne mreže. ...Pasivne tehnike filtriranja nisko-frekvencijskih struja smetnji pokazale su se nedostatnim, te se kombiniraju s aktivnim tehnikama. U radu su predložene aktivne metode potiskivanja zasnovane na odgovarajućem dizajnu mrežnog sučelja pretvarača glavnih i pomoćnih pogona i pripadne upravljačko-regulacijske strukture. Struje smetnji, pa tako i one nastale kao posljedica rada pretvarača glavnih i pomoćnih pogona instaliranih na vozilo, uzrokuju elektromagnetske smetnje koje mogu značajno utjecati na ispravan rad telekomunikacijske (TK) i signalno-sigurnosne (SS) infrastrukture uz prugu, a samim tim i na sigurnost željezničkog prometa. Stoga se potiskivanju nisko-frekvencijskih struja smetnji u pojnoj mreži treba pristupiti s posebnom pozornošću, koristeći pasivne/aktivne mjere. U svrhu ocjene kvalitete postignutih radnih karakteristika mrežnog sučelja pretvarača za napajanje glavnog pogona, u smislu potiskivanja struja smetnji, proveden je čitav niz pokusa mjerenja spektralnog sastava struja pojne mreže pod djelovanjem pretvarača u tipičnim uvjetima eksploatacije. Ispitivanja su provedena u laboratorijskim uvjetima, kao i na vozilu, uz zadovoljavajuće rezultate.
This paper presents an adaptive PWM control scheme of four-cell interleaved boost-type switching-mode rectifier, used as an input stage of auxiliary power supply of electrical vehicles, and its ...operation under regular, as well as under specific operating conditions - failure of one or more IGBTs.
Enterprise resource planning (ERP) systems are highly complex and their development is very long and expensive. The market needs to be defined in order to develop and maintain ERP systems. Croatian ...vendors need to be competitive in both domestic and foreign market, due to the size of the domestic market. The research indicates that only a small number of Croatian ERP systems vendors have linguistically adjusted their product to the demands of the foreign market. Linguistical support is essential for foreign market distribution and this situation can be resolved by preparing technology that would allow ERP systems vendors to translate the system in multiple languages in a simple, fast and cheap way. The application of standard software component with the support of publicly accessible on-line translation service would fasten the ERP systems translation process and reduce its price. The system would be ready to use instantly, and the translator could verify and upgrade local translation base when necessary (human aided machine translation). PUBLICATION ABSTRACT
New prototype of an auxiliary soft-switching power supply for the tram of the city of Zagreb was developed and built based on specifications of the existing auxiliary hard-switching power supply. A ...new soft-switching topology for the input DC-DC converter is proposed. It was possible to compare two power supplies built to the same specifications with only one basic difference: switching technology. Switching frequency of both supplies is equal and to lower the audible noise is fixed at 20 kHz. Experimental results are shown. A high efficiency of 97 % is achieved for the input soft-switching DC-DC converter and overall efficiency of the new auxiliary power supply is 92,5 %. Compared to the existing auxiliary power supply based on hard-switching technology, efficiency, weight and volume are substantially reduced.
High performance control system, necessary to implement advanced concept for dominantly soft-switching based IGBT converter for traction applications, auxiliary power supply for light rail vehicles, ...is described with more detailed insight in some specific control solutions. Those control solutions, implemented by very compact hardware, based on DSP-FPGA digital core module, and its analogue module counterpart, enabled accomplishment of enhanced dynamic characteristics of the converter, as well as improvements with respect to the converter's power density, as well as the achieved reduction of size and mass of the converter.
A simple method for determination of the counterion binding parameter (α) and aggregation number (N) from conductivity data is proposed. The method is based on fitting the values of the first ...derivative of conductivity (κ) versus total surfactant concentration (ct) function according to the equation derived from the mass action model (MAM) by using different conductivity models. Sodium dodecylsulphate (SDS) and dodecyltrimethylammonium bromide (DTAB) were chosen for validation of the proposed method. It was shown that the method gives a fairly accurate values for micellisation parameters of SDS (N=51–64, α=0.74–0.75) and DTAB (N=56–62, α=0.77–0.79), both in good agreement with the literature data. In addition, application of the proposed method does not require the value of the critical micelle concentration (cmc).
Conductivity models: A method for simultaneous determination of the micellar parameters from the conductivity data is proposed. The method is based on fitting the values of the first derivative of conductivity versus total surfactant concentration function, according to the equation derived from the mass action model using different conductivity models. An example of the fit is shown here, open circles represent the experimental data and the line, the calculated values.
Phase diagrams of binary symmetric double-tailed alkylbenzenesulfonate surfactant/water systems, as well as the structure of the phases, were determined using crossed polars, polarized light ...microscopy,2H NMR spectroscopy, Nomarski differential interference contrast optics, and cryo-transmission electron microscopy. The isotropic phase, the lamellar phase, and a high-viscosity solution representing an intermediate between the isotropic phase and the mesophase, which refers to the beginning of the formation of vesicles, were found. As may be expected, the isotropic phases at higher concentrations are formed mostly at higher temperatures. Isotropic regions are followed by regions characterized as the isotropic solutions containing vesicles; the optically isotropic phase contains a lamellar dispersion of vesicles in solution. The viscosity of these phases is found to be high near the borderline of the two-phase regions. At the same concentrations two-phase regions were found to contain the isotropic + lamellar phases at the higher temperature and the isotropic + crystalline phase at the lower temperature. Molecular-mechanical and semiempirical quantum-mechanical calculation searches for the global minimum in the conformational space of alkylbenzenesulfonate ions were conducted to examine the influence of monomer molecular structure on the micellar shape.
Asocijacija molekula površinski aktivnih tvari (PAT), rast i agregacija samoasocijata u lamelarne dvoslojeve (fleksibilne i zatvorene), micele, vezikule i tekuće kristale, predstavljaju važna ...temeljna istraživanja s primjenom - između ostalog - na transmembranska svojstva vezikula u prijenosu i enkapsulaciji lijekova. Među mnogim praktičnim upotrebama amfifilni agregati predstavljaju mogućnost primjene dobro definiranih dvoslojeva i multislojeva liotropnih mezotaza za kozmetičku i faimaceutsku industriju. Asocijati katanionskih PAT pokazuju široku raznovrsnost oblika, veličina i strukture čestica pa je moguće proizvesti nove materijale različitih svojstava. Vezikule mogu nastajati spontano kao rezultat samo nakupljanja fleksibilnih monoslojeva u jednoslojne i višeslojne meke čestice sa zatvorenim dvoslojevima. U ovom radu istraživanja su provedena u katanionskim smjesama natrijevoga n dodecilbenzensulfonata (SDBS) i didodecildimetil amonijevoga bromida (DDAB) u vodi te u vodenim otopinama neionskoga dvolančanog PAT, 4-(l-pentilheptil)benzensulfonata (6SDBS). Određivanje faznoga dijagrama, područja stvaranja micela i vezikula te faznih prijelaza, određivanje unutarnjih i vanjskih struktura čestica, provedeno je s pomoću metode raspršenja svjetlosti, raspršenja X zraka pod malim kutom te drugih komplementarnih metoda, npr. reoloških mjerenja u pseudo-izotropnim područjima koja dobro indiciraju stvaranje micela i vezikula karakterizirano kritičnim micelizacijskim i vezikularnim koncentracijama. Dodatno, mezofaze su istraživane polarizacijskom i elektronskom mikroskopijom.