Abstract
One of the main operation modes that characterizes power quality in distribution networks is asymmetry of three-phase voltage system. Operation of an induction motor (IM) with disturbed voltage symmetry in the supply network can not be considered as a rated one. The system of voltages applied to the stator winding of IM under these conditions contains positive- and negative-sequence components. This worsens the performance characteristics of IM essentially. In order to balance the 0.38 kV network operation and enhance the efficiency of the three-phase electric motor operation it is suggested to use a special balancing unit (BU) that minimizes the negative-sequence components of current and voltage. The operation modes of the obtained system “supply source – induction motor – balancing unit” are simulated within the MATLAB software package of applied programs, which allows one to assess the impact of low quality of power on the operating characteristics of the electric motor and the efficiency of the balancing unit to increase the “durability” of the motor under the asymmetrical power consumption.
Highlights
The coefficient of negative-sequence voltages should be considered as the main index of power quality that characterizes the level of voltage asymmetry in threephase three-wire networks: K 2U
The operation of induction motors under voltage asymmetry is complicated by the emergence of symmetrical components of the negative-sequence current
Numerous researches in the field of creation of imitating models of operation of the electric motor practically did not consider its work in the asymmetrical mode [2 - 11]
Summary
The coefficient of negative-sequence voltages should be considered as the main index of power quality that characterizes the level of voltage asymmetry in threephase three-wire networks:. The operation of induction motors under voltage asymmetry is complicated by the emergence of symmetrical components of the negative-sequence current. This causes additional power losses in the windings of rotor and stator which result in local overheating and affect greatly the motor lifetime and operation stability. Such losses for three-phase threewire (without zero wire) electric networks can be assessed using a coefficient of additional power losses [1]: KP. An aggregate impact of asymmetrical currents and voltages at motor operation in an asymmetric electric network causes a considerable change in its operating characteristics
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