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Diagnosis of voltage unbalance state in a system with power converter

Oliszewski Stanisław, Dybkowski Mateusz

Diagnostyka

2024

Vol. 25, No. 3

art. no. 2024304

In the paper problem of power supply unbalance voltage states with the same Voltage Unbalance Factor (VUF) value for power converters is tackled. This factor is being used to assess the quality of power supply. There are many sources of voltage unbalance phenomenon such as system asymmetries and uneven distribution of demand throughout phases. Based on literature three unbalance states are presented: lines overvoltage, lines undervoltage and phase angle asymmetry. VUF value alone cannot provide information on the type of voltage unbalance state. Moreover, the same VUF percentage can be obtained for different amount of unbalanced phases. In this paper simulation experiments were conducted in order to obtain data of rectifier output voltage during different unbalance states with same VUF. Ripple, mean value and frequency components of said voltage were used in order to detect and categorise power supply voltage unbalance. Such approach does not require complex power quality measuring tools as power supply unbalance can be initially diagnosed using single voltage sensor.

Performance analysis of a modified three-phase induction motor with optimal capacitance fed by single-phase ac supply

Bumroongphuck Chavaporn, Kinnares Vijit

Przegląd Elektrotechniczny

2020

R. 96, nr 10

62--70

This paper proposes a performance analysis of a modified three-phase induction motor with optimal capacitance operating with a singlephase mains supply. The modified three-phase motor is described and analyzed. Based on analytical equations, calculation of optimal capacitance to minimize voltage unbalance and torque pulsations is performed. Moreover positive and negative components of voltages are revealed. A d-q-0 reference frame for dynamic performance analysis is used to investigate flux linkages and electromagnetic torque. The validity of the optimal capacitance is confirmed by experimental results, showing that the motor has the least voltage unbalance and the highest efficiency compared with other non-optimal capacitances. The experimental and simulation results are in good agreement.

W artykule analizowano właściwości zmodyfikowanego trójfazowego silnika indukcyjnego. Na podstawie modelu matematycznego wyznaczono optymalną pojemność przy minimalnej liczbie zwojów oraz pulsację momentu. Określono też dodatnie i ujemne składowe napięcia. Zbadanno też właściwości dynamiczne.