Petr Orsag

Interference between electric traction supply network and distribution power network - resonance phenomenon

Electric traction is one of the biggest appliances in power network and can have a significant influences on supply network. These influences include non-harmonic currents and voltages, unsymmetric loading of the three phase system or rapid fluctuation in power consumption. Traction network, feeding network, traction transformer and, in some cases, filtration-compensation unit, altogether form a system of inductivities, capacities and resistances. That is why resonances can occur in this system. This paper investigates these resonance phenomena in a traction transformer substation that feeds alternate electric traction. The paper includes a theoretical analysis of the problem, computer simulation, and results of measurements in the transformer substation where resonances were recorded.

Efficiency evaluation of various assemblies of variable speed drive

The paper presents results of experimental measurements of efficiency of variable speed drive assemblies and their analyses. These configurations of the drive have been tested: without any filtering devices, with an input AC reactor and broadband passive harmonic filters, and with output filtering, such as output reactor or sine-wave filter, respectively. These filtering devices are used to match the requirements of drive electromagnetic compatibility; nevertheless, they have an influence on drive efficiency. An assumption of drive efficiency decrease in the case these devices were used was confirmed and analyzed in this paper. Efficiency of individual units of the variable speed drive is also shown.

Solutions to increase the efficiency of induction motors

This paper presents possibilities to increase the efficiency of three-phase squirrel cage induction motors. The necessary legislative requirements are stated in the first part of the paper, which are basically the main reason for efficiency increasing. After that a theoretical basis and explanation of the design for efficiency increasing follow. The final part presents the results of measurements on the concrete samples of induction motors of different efficiency classes, their comparison, evaluation and comparison with the limits prescribed by the relevant standards.

Impact of mains power quality on operation characteristics of induction motor

The paper deals with the impact of chosen main power quality indices, such as the voltage distortion, the voltage unbalance and the voltage dip on operation characteristics of an induction motor rated at 4 kW fed from the frequency converter and AC source. In this paper the motor efficiency and motor power factor are analyzed in dependence on the motor load at rated motor frequency and the maximum permitted standard levels of power quality indices. In particular, it is shown that the greatest impact on motor operation characteristics has the voltage dip, and that the motor efficiency decreases approximately linearly with the level of the voltage distortion and the voltage unbalance in the specific range of motor load. To distinguish the energy characteristic differences, we used the standard deviation.

Track occupancy detection using ratio of open-circuit impedance to short-circuit impedance

This paper deals with the change of the ratio of the open circuit impedance to short-circuit impedance of the electric traction depending on the distance of the traction vehicle from the beginning of the section. This ratio is calculated in order to estimate the traction vehicle speed and the distance at which the track occupancy can be indicated. Therefore, the impedance moduli and the impedance phases of the open track circuit and the impedance of the occupied track (short-circuit impedance) is compared at different short-circuit distances. The impedances ratio varies with changing weather conditions. It is different in dry weather than in the rain. Therefore, in practical use, the track occupancy indicator must always be updated and the ratio must always be recalculated for the new situation. In this paper, the impedances ratio is calculated for specific parameters measured in the section of the track in Orlova. The distance between a reference point (place of short circuit rails) from a measuring point is for the impedance module ratio of F = 10 about 218 m.

The influence of nonharmonic voltage source on losses in induction motor

This paper deals with analysis of induction motor fed by non-harmonic voltage source. The losses are determined based on direct method for analysis of motor efficiency. The method is presented for fractional losses analysis with consideration harmonics generated by PMW. The introduced method earmarks the fundamental harmonic components of electrical magnitudes for comparison purposes of different harmonic and non-harmonic sourcing types. The motor losses harmonic effect influence is demonstrated on measuring case of induction motor fed by grid and PWM converter.

Power system studies of electrical drive test field using EMTP-ATP software

The aim of this paper is to present the power system studies - the approach, main results and design recommendations carried out as a design verification of the electrical drive test field. The drive test field is a specific problem, as unlike of standard industrial installation the exact types of connected loads differ and thus, the particular input data of connected loads are not known. The possible way of data mining and assumptions taken into account, as well as simulation inaccuracies, are presented here. All studies were performed in the EMTP-ATP software, and, if applicable, the approach and assessment of results was in accordance with EN standards or Czech PNE standards. The work also presents some useful points which should be a part of the executive summary of particular power system studies.

Harmonic analysis according to IEC 1000-2-6 of the newly designed drive test field using EMTP-ATP software

The aim of this paper is to present the approach of emission levels assessment in the power supply of industrial plant, including data mining and simplified rules for summation of harmonic voltages as described in internal Czech electrical plant power systems standards for distribution network operators. Besides to quality of supply voltages in the point of common coupling, and internal points of coupling, there is other useful information which should be mentioned in the executive summary, and are necessary to submit the overall electrical system study in this field.

The Enlarged d-q Model of Induction Motor with the Iron Loss and Saturation Effect of Magnetizing and Leakage Inductance

The main aim of this paper is the presentation of induction motor model with the iron loss and the saturation effect of magnetizing and leakage inductances. The previous published standard models of induction motor using the d-q model actually neglect the iron loss effect. Hence, the iron loss represents about 3–5 % total loss in the induction motor. This paper is focused on the inferred model, which considers the iron loss in motor, and comparing with the standard models. The second part of the paper deals with the saturation effect of magnetizing and leakage inductances.

An equivalent model of a single-phase load under non-sinusoidal conditions

This paper deals with modelling of a single-phase load under non-sinusoidal conditions based on a physical point of view and duality principle. The paper describes Kirchhoffs laws and the generalized Ohms law for rms values of load equivalent models, and presents some new theoretical aspects in this field. Finally, a comparison between our approach and two similar ones is performed.