Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Alexandr NOVOZHILOV"

Process Simulation in Induction Motor where Short-Circuit Rotor Bar is Failed during Run-down Regime DOI:10.15199/48.2018.06.06

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Damages from operation of an induction motor (IM) with a short-circuit rotor when its bars are broken are mainly expressed in increased power consumption [1]. At the same time, the cost of power over consumption for the year of operation of such IM often exceeds the cost of engine itself[2]. Due to this fact there are many proposals on how to diagnose this type of damage during operation[3,10-23]. However most of them cannot be realized because of the effect of electric network parameters fluctuations, IM vibrations and resistance moment variation load on the measured signal. These effects can be ignored if IM diagnosis is carried out during run-down regime[3, 24-25]. However under these conditions development of such a diagnostic system without process simulation in IM is impossible. IM run-down regime starts when it is disconnected from the power network. Immediately after IM switching off the currents in stator winding become equal to zero and currents in rotor winding remain the same as they were at the moment of shutdown. Thereafter due to the fact that active resistances are available in the rotor windings attenuation of them occurs. At the same time speed of rotor rotation slows down under the impact of resistance moment in IM bearings, its air fan and drive mechanism. As a result EMF is changed in stator windings not only in terms of magnitude but in frequency. Mathematical model of induction motor In order to simulate processes occurring when IM runsdown with a broken rotor bar it is convenient to use a mathematical model differential equations of which are compiled by the method of loop currents for phase-to-phase voltages[4]. According to this mathematical model, taking into account Fig. 1 (K keyswitch closed) and application (1)                    =[...]

Sources of independent power supply for protection relay DOI:10.15199/48.2018.05.04

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Nowadays, telemetry and relay protection, which are located directly on the protected element of the electric power system or inside of it are increasingly used in the electric power industry. For its supply, it requires an autonomous source of low power, which has a stabilized DC voltage. Existing devices are unreliable, expensive to manufacture and operate. This work offers power and relay protection and diagnostics with the help of autonomous power sources that can be used in the network with the help of current or voltage transformers, and with the help of an inductive converter placed in the end zone of an electric machine as well. Streszczenie. W pracy nalizowano metody niezależnego zasilania układów przekaźnikowych zabezpieczeń. Układy takie powinny charakteryszować się małym poborem mocy, niezawodnością I niską ceną. Źródła niezależnego zasilania układów zabezpieczeniowych Keywords: Relay protection, diagnostic devices, autonomous power supply, stabilized voltage Słowa kluczowe: przekaźniki, niezależne zasilanie, zabezpieczenia Introduction. Nowadays, protective relay and telemetry equipment, which are located directly on the protected element of the interconnected power system or inside it, are used in the electric power industry. Examples of such devices for high voltage overhead lines are peripheral telemetry posts for monitoring of gust-and-glaze loading [1] and single phaseto- earth fault protection [2, 14] and controlled network devices of D-FASTS type [3]. In electrical machines, such devices include overtemperature protection [4] and protection against electrical faults in stator windings [5], which are highly sensitive. In this case, the signal of faults in the electric machine is transmitted over the protective power cable using a power switch made up of two thyristors connected in parallel opposition. The use of new generation distributed network devices in electric power systems implies the use of independent D[...]

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