Inter-turn short circuit of field windings is a common electrical fault of generators.Simulation is an important method of investigating the fault and providing data support for fault monitoring.However,huge numbers o...Inter-turn short circuit of field windings is a common electrical fault of generators.Simulation is an important method of investigating the fault and providing data support for fault monitoring.However,huge numbers of pole pairs and damper loops in large hydro-generators would lead to lengthy calculation time,hindering scientific research and engineering application.To deal with this problem,we analyze a theoretical basis for a damper winding simplified model and then propose an equivalent treatment method.Through the analysis of steady-state current harmonic characteristics of generators with different stator winding configurations during the fault,the simplified models suitable for steady-state calculation are derived from two aspects,namely,additional rotor harmonic current frequency characteristics and the relationship of the amplitude as well as the phase of each branch current of the stator.The calculation and experimental results of the two simplified models are then compared to verify the models' correctness.A calculation example of the Three Gorges left bank VGS generator shows few deviations between the calculation results of the simplified model and the original model.Moreover,the calculation time using the simplified model is 1/1500 that using the original model,which provides a more effective tool for on-line fault monitoring.Finally,the sensitivity-verification application of the fault-monitoring scheme based on the stator steady-state unbalanced current RMS is depicted.The result shows that the scheme can monitor two-turn short circuits of field windings in the Three Gorges generator and provide high sensitivity.展开更多
This paper presents a method of establishing simplified equivalent circuit model of traveling wave ultrasonic motor by using 1/2 wavelength stator with the similar vibration characteristics. Combined with the vibratio...This paper presents a method of establishing simplified equivalent circuit model of traveling wave ultrasonic motor by using 1/2 wavelength stator with the similar vibration characteristics. Combined with the vibration mode characteristics of the composite stator, the method utilizes Hamilton principle to obtain precise solution of the simplified equivalent circuit. The model shows the mechanism of ultrasonic motor, considering the influence of non-axisymmetric vibration mode, tooth outline, anisotropy of PZT (Piezoelectric ceramic), etc. With this method, various electric parameters corresponding to different vibration modes, such as static capacitance, dynamic capacitance, dynamic inductance, dynamic resistance, equivalent input impedance, etc., can be solved. Experiments show good agreement with theoretical results.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50807027)the China Postdoctoral Science Foundation(Grant No. 2012M520155)the Fundamental Research Funds for the Central Universities (Grant No. 2013JBM081)
文摘Inter-turn short circuit of field windings is a common electrical fault of generators.Simulation is an important method of investigating the fault and providing data support for fault monitoring.However,huge numbers of pole pairs and damper loops in large hydro-generators would lead to lengthy calculation time,hindering scientific research and engineering application.To deal with this problem,we analyze a theoretical basis for a damper winding simplified model and then propose an equivalent treatment method.Through the analysis of steady-state current harmonic characteristics of generators with different stator winding configurations during the fault,the simplified models suitable for steady-state calculation are derived from two aspects,namely,additional rotor harmonic current frequency characteristics and the relationship of the amplitude as well as the phase of each branch current of the stator.The calculation and experimental results of the two simplified models are then compared to verify the models' correctness.A calculation example of the Three Gorges left bank VGS generator shows few deviations between the calculation results of the simplified model and the original model.Moreover,the calculation time using the simplified model is 1/1500 that using the original model,which provides a more effective tool for on-line fault monitoring.Finally,the sensitivity-verification application of the fault-monitoring scheme based on the stator steady-state unbalanced current RMS is depicted.The result shows that the scheme can monitor two-turn short circuits of field windings in the Three Gorges generator and provide high sensitivity.
文摘This paper presents a method of establishing simplified equivalent circuit model of traveling wave ultrasonic motor by using 1/2 wavelength stator with the similar vibration characteristics. Combined with the vibration mode characteristics of the composite stator, the method utilizes Hamilton principle to obtain precise solution of the simplified equivalent circuit. The model shows the mechanism of ultrasonic motor, considering the influence of non-axisymmetric vibration mode, tooth outline, anisotropy of PZT (Piezoelectric ceramic), etc. With this method, various electric parameters corresponding to different vibration modes, such as static capacitance, dynamic capacitance, dynamic inductance, dynamic resistance, equivalent input impedance, etc., can be solved. Experiments show good agreement with theoretical results.
