Wyniki 1-3 spośród 3 dla zapytania: authorDesc:"Viacheslav MELNYKOV"

Sensorless vector-control system with the correction of stator windings asymmetry in induction motor

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Estimation of induction motor stator windings asymmetry influence on power and dynamic characteristics of sensorless vector control systems is performed. A system of vector control in a three-phase coordinate system is developed. This system makes it possible to compensate for induction motor windings asymmetry by correction of flux linkage assignment. Streszczenie. Analizowano wpływ asymetrii uzwojeń twornika silnika indukcyjnego na właściwości dynamiczne przy sterowaniu bezczujnikowym. Badano układ silnika trójfazowego. Przedstawiono metody korekcji wpływu asymetrii uzwojeń. (Bezczujnikowe wektorowe sterowanie silnikiem indukcyjnym z korekcją asymetrii uzwojeń) Key words: asymmetry, stator windings, power characteristics, vector control system. Słowa kluczowe: silnik indukcyjny, sterowanie bezczujnikowe, asymetria uzwojeń Introduction Sensorless induction motor (IM) vector control systems (VCS) are widely spread in industry. Long-term performance of IM results in occurrence of various damages. As diagnostics results show [1], at present, a great number of IM with unsymmetrical stator windings are used. According to statistic data, more than half IM failures occur due to stator windings damages [2, 3]. The main reason for this consists in damages of conductor and slot insulation which can be caused by both violation of motor production or repair methods and abuse. It results in short circuits: winding short circuits, interfacial ones and ironwork faults [4, 5]. As, due to the crisis, industrial enterprises reduce the amount of repair work, when some sections of stator winding of high- and medium-power motors fail, these sections are not removed out of the slots, but are excluded from the circuit and the sections ends are connected passing over the faulty ones [3]. As a result, the stator winding becomes asymmetric and henceforth the motor operates with this winding. Consequences of operation of IM with unsymmetrical stator wi[...]

The review of methods and systems of the fault-tolerant control of variable-frequency electric drives DOI:10.15199/48.2019.01.36

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Introduction Correct functioning of variable-frequency electric drives (VFD) with induction motors (IM) depends on the reliable operation of IM, a three-phase autonomous voltage invertor (AVI), and a control system (CS). IM malfunctions include failures of: - one or several phases of the stator; - electrical asymmetry; - magnetic asymmetry; - mechanical breaks, etc. AVI malfunctions include: - the failure of a separate semiconductor switch; - the failure of one or two invertor arms; - the malfunction or failure of the control driver, etc. CS malfunctions include: - the break of angular rotation frequency sensor; - the break of the current sensors; - the breaks at the formation of the control signals, etc. The share of IM malfunction is the biggest in the whole scope of VFD failures. When IM operates with insignificant defects or with the breaks at the early stages of their development the system maintains its operability. In this case the quality of control deteriorates; the indices of the energy efficiency of the process of the electromechanical energy conversion decreases, the losses increase essentially and variable components of the electromagnetic torque and consumed active power appear. In such cases fault-tolerant control systems (FTC) are of great interest. They usually consist of two parts: the system of diagnostics and fault revelation and the system of the formation of special control impacts for their compensation. The scope of FTC systems is determined by the elements for which it is important to maintain an operational state in case of damage, despite the reduction in power, speed and energy efficiency: - electric transport drive; - electric drive of critically important technological objects; - electric drive of fire pumps, pumping stations of public water supply and water disposal; - electric drive of ventilation systems. Problem statement With the given significant number of developed fault toler[...]

Decrease of the thermal overloads of a variable-frequency electric drive at damages in the electric circuit of an induction motor stator DOI:10.15199/48.2019.05.11

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Damages in the stator power electric circuits stand out of the main causes of induction motors (IM) failure. Therefore, according to the research [1], the cause of 25% - 40% of IM failures consists in turn-to-turn shorting resulting from the stator winding insulation damages. The occurrence of turnto- turn shorting in the windings of IM of alternating current variable-frequency electric drives (ED) results in local overheat of particular semiconductor switches of frequency convertors (FC). A break of the whole winding or a parallel section of IM phase winding is a logical development of the turn-to-turn shorting. For IM with the number of parallel winding paths exceeding four a break of one path results in the asymmetry of the stator winding three-phase system and usually ends in the motor emergency outage. ED operation with asymmetric windings of the stator phases may also result in thermal overloads of particular FC switches and IM phases [2]. Timely detection and elimination of IM damages at the early stages of their development may increase the life span of the technological equipment and reduce the financial losses caused by unpredictable disconnection of the equipment resulting from technological faults or IM failure. Thus, fault-tolerant control systems (FTC) are of special interest as they are able to detect various types of damages at the initial stage and operatively adapt the control law in such a way that ED functionality remains for a long time till there is a possibility of IM repair or change [3]. There are two groups of the conventional methods of fault-tolerant control of IM with damages in the stator power electric circuit. The first group includes methods only allowing the detection of occurring damages and the termination of ED operation at their further development [4, 5]. This group may also include software redundancy methods based on the switch between the control algorithms from complex to simpler[...]

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