Symmetrical and unsymmetrical voltage sags are a major cause of energy loss in induction motors affecting the efficiency and longevity of the motor. A comprehensive and novel graphical method to determine energy loss during unsymmetrical sags is proposed. The energy is computed using torque-speed characteristics of the induction motor. Due to unbalance in the voltages during unsymmetrical sags, oscillations are observed in torque-speed characteristics. Throughout these oscillations, motor torque and speed attain extreme values. Area under the curve of torque and speed during oscillation is computed using MATLAB/Simulink simulation, which is a measure of the output power during unsymmetrical sags. The sag duration is measured to compute the energy loss. The analytical expression to assess output power of an induction motor during unsymmetrical sag is derived. The graphical results are validated using analytical calculations. Graphical representation is easy and faster to construct than analytical methods; in addition, the graphical method proposed makes it easier to assess the comparative magnitudes. Assessment of energy loss provides a useful tool for optimal injection of energy for sag mitigation techniques.

中文翻译：

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感应电机不对称电压暂降期间能量损失的计算__图解法


对称和不对称电压暂降是感应电机能量损失的主要原因，影响电机的效率和寿命。提出了一种全面且新颖的图形方法来确定不对称凹陷期间的能量损失。使用感应电机的扭矩-速度特性计算能量。由于不对称暂降期间电压不平衡，在扭矩-速度特性中观察到振荡。在这些振荡过程中，电机扭矩和速度达到极值。使用 MATLAB/Simulink 仿真计算振荡期间扭矩和速度曲线下的面积，这是不对称凹陷期间输出功率的度量。测量暂降持续时间以计算能量损失。推导了评估异步电机在不对称凹陷期间输出功率的解析表达式。使用分析计算验证图形结果。图形表示比分析方法更容易、更快速地构建；此外，所提出的图形方法可以更容易地评估比较幅度。能量损失评估为缓解电压骤降技术的最佳能量注入提供了有用的工具。