When the machine is at high speed, serious problems occur, such as high frequency loss, difficult thermal management, and the rotor structural strength insufficiency. In this paper, the performances of two high-speed permanent magnet generators (HSP- MGs) with different rotational speeds and the same torque are compared and analyzed. The two-dimensional finite element model (FEM) of the 117 kW, 60 000 rpm HSPMG is established. By comparing a calculation result and test data, the accuracy of the model is verified. On this basis, the 40 kW, 20 000 rpm HSPMG is designed and the FEM is established. The relationship between the voltage regulation sensitivity and power factor of the two HSPMGs is determined. The influence mechanism of the voltage regulation sensitivity is further revealed. In addition, the air-gap flux density is decomposed by the Fourier transform principle, and the influence degree of different harmonic orders on the HSPMG performance is determined. The method to reduce the harmonic content is further proposed. Finally, the method to improve the HSPMG overload capacity is obtained by studying the maximum power. The research showed that the HSPMG at low speed (20 000 rpm) has high sensitivity of the voltage regulation, while the HSPMG at high speed (60 000 rpm) is superior to the HSPMG at low speed in reducing the harmonic content and increasing the overload capacity.
This paper analyzes the concept of context with a special focus on the context of communication. We suggest two ways of classifying approaches to the context of communication: (i) classifying approaches based on a number of relevant dimensions for analyzing context in social activities, (ii) classifying approaches, based on the dimensions of Peirce’s semiotics. We also discuss the use of collected corpora of language, especially multimodal corpora of spoken interaction, as an aid in studying context. Finally, building on the two ways of classifying approaches to the context of communication, we present our own proposal for how to analyze the main relevant contextual dimensions influencing human interaction and communication.
One of the most important business areas of the company is the management of working capital. Energy companies that produce electricity and heat are the main consumers of steam coal, so their decision concerning stock levels is a major determinant of supply schedules. These decisions depend on legal and technical requirements as well as economic aspects. The seasonality of coal consumption jointly with pre-purchase costs and storage costs has a straight impact on delivery scheduling in a parabolic way. There is a divergence in expectations regarding delivery schedules among the coal market participants (energy, mining, transport companies). The purpose of this article is to present the concept of pricing of steam coal and transport service on the Polish market, assuming the use of price incentives, resulting in delivery scheduling during the year. The article presents selected theoretical content in the field of coal logistics and working capital management in the company, the expectations of the steam coal market participant regarding delivery schedules have been identified. The proposed concept of pricing steam coal and transport service should be discussed further in scientific and expert work.
Field programmable analog arrays (FPAA), thanks to their flexibility and reconfigurability, give the designers quite new possibilities in analog circuit design. The number of both academic projects on FPAA and applications of commercially available programmable devices is still growing. This paper explores the properties and parameters of two most popular FPAA circuits: the AnadigmVortex AN221E04 and AnadigmApex AN231E04 from the Anadigm company. The research conducted by the authors led to the discovery of some undocumented features of these devices. Several applications for audio processing were built and tested. The results show that these circuits can be used in medium-demanding audio applications. Thanks to dynamic reconfigurability, they also allow to build an universal analog audio signal processor. These circuits can also act as a versatile platform for rapid prototyping and educational purposes.
The paper presents the method of probabilistic optimisation of load bearing capacity and reliability of statically indeterminate bar structures, and of coupling of members in kinematically admissible failure mechanisms (KAFM), which contain minimal critical sets of elements (MCSE). The latter are characterised by the fact that if only a single element is operational, the whole set is operational too. A method of increasing load bearing capacity and reliability of KAFM built from bars dimensioned in accordance with the code is presented. The paper also shows estimation of load bearing capacity and reliability of KAFM of the optimised structures containing elastic-plastic bars with quasi-brittle connections with nodes. The necessity of increasing connection of load bearing capacity and reliability in relation to bar reliability in order to prevent bars from being excluded from MCSE due to connection fracture is estimated.
This paper presents a computationally efficient method for modelling an impact of the converter drive on the power grid. The formalized variable structure method (FVSM) allows for comprehensive studies of the effect on the power grid and examining the relation between this effect and the number of drive and feeding line parameters. In order to obtain a comprehensive model along with the model of the power grid, the parameters that are applied originate from a drive of a coal-fired power station. These parameters have been determined based on assessment and estimation. The estimation process was conducted with the aid of a model that allows for the commutation of power electronic elements. The authors confirmed that the model was correct by comparing empirical and theoretical voltage and current waveforms. Harmonic content of the voltage and current in the power grid which feeds the drive are considered to be the measure of the converter drive impact on the power grid. The standard method for the reduction of a harmonic content in the voltage and current involves the application of line reactors and distribution or converter transformers. As an example, the authors determine the impact of the drive on the power grid with respect to the adopted parameters of the line reactor. This example presents FVSM abilities with regard to simulation of complex systems that contain power grid components and converter drives.