Limiting the influence of regulated electrical drainage on track circuits

For the past two years, the authors of this paper have been working on the development of a new regulated electrical drainage system for tram tracks, which may also be used on railways in the future. When this drainage is used on train tracks equipped with track circuits, it is necessary to make sure that the drainage does not generate current harmonics which may be dangerous for the correct functioning of the circuits. In the Czech Republic, requirements regarding the operation of track circuits are stated by Standard CSN 342613. When the drainage was tested on tram tracks, where there are no track circuits, it was found out that in certain operation modes, the drainage generates frequencies which collide with the frequencies of track circuits. Therefore, a passive filter was designed to solve this problem. With the use of computer simulation and measurements on a laboratory model, it was verified that this filter is able to suppress unwanted current harmonics, so that they are in agreement with the above mentioned Standard. These measurements and simulations are described in this paper.Web of Science245565

Low-cost extra-low voltage LED dimmer for tuneable white lighting

The colour appearance of light sources has a major impact on how people perceive space. With LED illumination lighting, the colour output can be tuned to virtually any perceivable colour, including any hue of white light. It has been established that the right shade of white light during the 24-hour day cycle has a positive effect on the human body's biological system. For this reason, it is very important to focus on the development and application of new lighting systems that have dynamically variable light outputs in order to imitate the sunlight. Circadian regulation is most responsive to short-wavelength light (460 nm = blue colour). This paper describes the development of a low-cost extra-low voltage LED dimmer for tunable white lighting systems aiming to achieve maximum electrical performance and light-output. This dimming module has two independent LED control channels and allows for a variable colour temperature control from warm white to cold white light. Experimental results of the dimming module efficiency measurements, correlated colour temperature (CCT), colour rendering index (CRI), illuminance and power consumption of the luminaire depending on the duty cycle for different control frequencies (200 Hz, 1.5 kHz, 5 kHz, 10 kHz and 20 kHz) are presented. The paper further describes the principle of creating control curves for an independent regulation of correlated colour temperature and illuminance. In the form of a table, the control curve outputs may be uploaded into a microcontroller. The paper details the construction, function and the advantages of this LED dimmer prototype.Web of Science253494

Towards the text compression based feature extraction in high impedance fault detection

High impedance faults of medium voltage overhead lines with covered conductors can be identified by the presence of partial discharges. Despite it is a subject of research for more than 60 years, online partial discharges detection is always a challenge, especially in environment with heavy background noise. In this paper, a new approach for partial discharge pattern recognition is presented. All results were obtained on data, acquired from real 22 kV medium voltage overhead power line with covered conductors. The proposed method is based on a text compression algorithm and it serves as a signal similarity estimation, applied for the first time on partial discharge pattern. Its relevancy is examined by three different variations of classification model. The improvement gained on an already deployed model proves its quality.Web of Science1211art. no. 214

Laboratory device detecting the magnitude of the static friction coefficient of brake lining

The paper describes the design of laboratory equipment, which was created for verification and determination of the value of the static coefficient of friction in the contact surfaces of the brake lining and the brake drum of the drum brake with external shoes by experimental procedure. Suppliers of brake linings state the values of the friction coefficients which correspond to different operating temperatures, but do not state the values of the friction coefficient of the respective brake lining with regard to the state of contamination of the contact surfaces. In practice, the brake contact surfaces are exposed to moisture, dust, lubricants and oils; these weather and operational influences significantly affect the value of the coefficient of friction. The results of the laboratory tests performed with two types of brake linings (commonly used in practice) (fabric, hardened rubber) show that the coefficient of friction of a given brake lining is strongly influenced by the state of contamination of the contact surfaces.Web of Science15219719

Innovative bidirectional isolated high-power density on-board charge for vehicle-to-grid

This paper deals with developing and implementing a bidirectional galvanically isolated on-board charger of a high-power density. The power density of the new charger was 4 kW/kg and 2.46 kW/dm(3), and the maximum efficiency was 96.4% at 3.4 kW. Due to the requirement to achieve a high-power density, a single-stage inverter topology was used. Regarding switching losses, due to the topology of the circuit with so-called hard switching, the switching frequency was set to 150 kHz. A laboratory prototype was built to verify the properties and operating principles of the described charger topology. The on-board charger has been tested in a microgrid test platform. Due to the parasitic properties of the transformer and other electronic components, overvoltage with subsequent oscillations occurred on the primary side of the transformer and damped resonance on its secondary side. These parasitic properties caused interference and especially voltage stress on the semiconductor elements. These undesirable phenomena have been eliminated by adding an active element to the charger topology and a new transistor control strategy. This new switching control strategy of transistors has been patented.Web of Science2221art. no. 847

همبستگی عزت نفس با پیشرفت تحصیلی در دانشجویان دانشکده‌ی پرستاری و مامایی زنجان 1388

زمینه و هدف: یکی از بزرگترین معضلات آموزشی، افت تحصیلی دانشجویان است. بنابراین توجه به بهداشت روانی و پیشرفت تحصیلی این گروه اهمیت به‌سزایی دارد. پاره‌ای از مطالعات بیانگر ارتباط مستقیم بین عزت نفس و پیشرفت تحصیلی است، لیکن بعضی از صاحب نظران رابطه‌ی مستقیم این دو را مورد تردید قرار داده‌اند. این پژوهش با هدف تعیین همبستگی عزت نفس با پیشرفت تحصیلی دانشجویان دانشکده‌ی پرستاری و مامایی زنجان انجام شده است. روش بررسی: این پژوهش یک مطالعه‌ی همبستگی بود، کلیه‌ی دانشجویان دانشکده‌ی پرستاری و مامایی زنجان که حداقل دو نیم‌سال سابقه‌ی تحصیلی داشتند، (182 نفر) در مطالعه شرکت کردند. ابزار جمع‌آوری اطلاعات پرسش‌نامه بود. پرسش‌نامه از دو بخش شامل: ویژگی‌های فردی و تحصیلی واحدهای پژوهش و آزمون 58 سوالی عزت نفس کوپراسمیت تشکیل شده بود. یافته‌ها: ضریب همبستگی پیرسون رابطه‌ی معنی‌داری بین عزت نفس و پیشرفت تحصیلی دانشجویان نشان داد (31/0= r ). ولی عزت نفس با سن و جنسیت ارتباط آماری معنی‌داری نداشت (05/0 P ). نتیجه‌گیری: با توجه به وجود همبستگی مثبت بین عزت نفس و پیشرفت تحصیلی دانشجویان، به نظر می‌رسد استفاده از روش‌های تقویت عزت نفس می‌تواند در جلوگیری از افت تحصیلی دانشجویان نقش داشته باشد

Řídící jednotka trojfázového střídače pro laboratorní úlohu z výkonové elektroniky

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta elektrotechniky a informatiky. Katedra (448) výkonové elektroniky a elektrických pohon

Application of fuzzy logic in control of switched reluctance motor

The flux linkage of switched reluctance motor (SRM) depends on the stator current and position between the rotor and stator poles. The fact determines that during control of SRM current with the help of classical PI controllers in a wide regulation range unsatisfied results occur. The main reasons of the mentioned situation are big changes of the stator inductance depending on the stator current and rotor position. In a switched reluctance motor the stator phase inductance is a non-linear function of the stator phase current and rotor position. Fuzzy controller and fuzzy logic are generally non-linear systems; hence they can provide better performance in this case. Fuzzy controller is mostly presented as a direct fuzzy controller or as a system, which realizes continued changing parameters of other controller, so-called fuzzy supervisor. Referring to the usage of fuzzy logic as a supervisor of conventional PI controller in control of SRM possible improvement occurs

Elektrický regulovaný pohon se spínaným reluktančním motorem bez snímače polohy rotoru

Import 31/07/2008Prezenční448 - Katedra elektronikyNeuveden

Improving power quality with the use of a new method of serial active power filter (SAPF) control

The quality of electric energy has currently become a widely discussed issue. The operation of appliances with nonlinear power consumption and with harmonic distorted current leads to voltage drops on network impedance, which in turn leads to power voltage distortion. To transform the distorted network voltage into harmonic voltage and thus improve the quality of electric energy, it is possible to use serial active power filters. SAPF can also be used as line conditioners. These devices are able to regulate supply voltage at the ends of a distribution grid, so that it meets the relevant standards. Line conditioners are also used in the increasingly widespread off grid systems. This paper deals with serial active power filter control. A new control method, called "comparative method", is presented. The efficiency of this method is demonstrated by measurement results, and compared with standard methods of active power filter control, such as the Butterworth filter method, or the Fast Fourier Transform based method.Web of Science231201