Frequency Characteristics of Generator Stator Windings

2013 ◽  
pp. 151-183
Author(s):  
Charles Su
Keyword(s):  
Pulse Propagation ◽  
Low Voltage ◽  
Travelling Wave ◽  
Wave Mode ◽  
Frequency Characteristics ◽  
Capacitive Coupling ◽  
Stator Winding ◽  
Stator Windings ◽  
Steel Core ◽  
Generator Stator

A generator stator winding consists of a number of stator bars and overhang connections. Due to the complicated winding structure and the steel core, the attenuation and distortion of a pulse transmitted through the winding are complicated, and frequency-dependent. In this chapter, pulse propagation through stator windings is explained through the analysis of different winding models, and using experimental data from several generators. A low voltage impulse method and digital analysis techniques to determine the frequency characteristics of the winding are described. The frequency characteristics of generator stator windings are discussed in some detail. The concepts of the travelling wave mode and capacitive coupling mode propagations along stator winding, useful in insulation design, transient voltage analysis, and partial discharge location are also discussed. The analysis presented in this chapter could be applied to other rotating machines such as high voltage motors.

scholarly journals FREQUENCY CHARACTERISTICS OF ELECTRICAL MACHINES WITH A MESH WINDING DURING HEAT-AND-MOISTURE AGING

2021 ◽  
pp. 59-66
Author(s):  
V. Chumak ◽  
O. Timoshuk ◽  
Е. Monakhov ◽  
А. Vishnevsky ◽  
А. Stulishenko
Keyword(s):  
Electric Motor ◽  
Low Voltage ◽  
Short Circuit ◽  
Area Under The Curve ◽  
Electric Circuit ◽  
Frequency Characteristics ◽  
Diagnostic Features ◽  
Stator Windings ◽  
Steel Core ◽  
Periodic Monitoring

Operation of an electric drive with damages in power electric circuit of the motor stator results in asymmetry of the motor phase current charge, increase of heating losses in certain phases, occurrence of variable components of electromagnetic torque and consumed power. An electric motor stator winding consists of a number of stator bars and overhang connections. Due to the complicated winding structure and the steel core, the attenuation and distortion of a pulse transmitted through the winding are complicated, and frequency-dependent. A low voltage impulse method and digital analysis techniques to determine the frequency characteristics of the winding are described. The frequency characteristics of electric motor stator windings are discussed in some detail. The analysis presented in this chapter could be applied to other rotating machines such as low voltage motors. An experiment of damping of electric motor wilding was conducted. Changes in frequency characteristics after the cycle are shown. In this article an analysis of the frequency characteristics of low-voltage electric machines with mush-wound windings, taking into account the processes of successive destruction of the insulation structure by the influence of heat-wet cycles. It is shown that the frequency characteristics can be generalized by the parameter of the state of isolation in the conditions of periodic monitoring of the quality of insulation during regulatory audits. It is proved that the frequency characteristics taken in idle and short-circuit modes have diagnostic features of the level of insulation destruction during humidification, which consist of shifting the characteristics of extremes into the region of lower frequencies, as well as reducing the area under the curve between the minimum and maximum extrema of the characteristic.

Generator Stator End Winding Resonance: Problems and Solutions

2013 ◽  
Author(s):  
Bill Moore ◽  
Clyde Maughan
Keyword(s):  
Visual Inspection ◽  
Fatigue Cracking ◽  
Vibration Monitoring ◽  
Stator Winding ◽  
Resonant Vibration ◽  
Primary Methods ◽  
Stator Windings ◽  
Problems And Solutions ◽  
On Line ◽  
Generator Stator

Stator windings that are in resonance will have high levels of vibration, if not properly damped or braced. Windings in resonance can suffer from early conductor strand fatigue cracking, arcing and failure during operation. Evidence of high vibration can sometimes be seen through visual inspection, with observance of dusting and greasing. There are two primary methods to anticipate and detect end winding resonant vibration — the bump test and on-line monitoring. Both are important and play a key role in identifying stator winding resonance problems, as well as implementing the appropriate solution. This paper will discuss the reasons that stator end winding resonance occurs. The technology, as well as the advantages and limitations of both the bump test and vibration monitoring, will be discussed. Solution approaches to end winding vibration are included, as well as one case history.

Comparison of the Influence Coefficient Method and Travelling Wave Mode Approach for the Calculation of Aerodynamic Damping of Centrifugal Compressors and Axial Turbines

2017 ◽  
Author(s):  
K. Vogel ◽  
A. D. Naidu ◽  
M. Fischer
Keyword(s):  
Centrifugal Compressor ◽  
Travelling Wave ◽  
Wave Mode ◽  
Forced Response ◽  
Computational Time ◽  
Influence Coefficient ◽  
Average Deviation ◽  
Aerodynamic Damping ◽  
Influence Coefficients ◽  
Periodic Boundaries

The prediction of aerodynamic damping is a key step towards high fidelity forced response calculations. Without the knowledge of absolute damping values, the resulting stresses from forced response calculations are often afflicted with large uncertainties. In addition, with the knowledge of the aerodynamic damping the aeroelastic contribution to mistuning can be considered. The first section of this paper compares two methods of one-way-coupled aerodynamic damping computations on an axial turbine. Those methods are: the aerodynamic influence coefficient, and the travelling wave mode method. Excellent agreement between the two methods is found with significant differences in required computational time. The average deviation between all methods for the transonic turbine is 4%. Additionally, the use of transient blade row methods with phase lagged periodic boundaries are investigated and the influence of periodic boundaries on the aerodynamic influence coefficients are assessed. A total of 23 out of 33 passages are needed to remove all influence from the periodic boundaries for the present configuration. The second part of the paper presents the aerodynamic damping calculations for a centrifugal compressor. Simulations are predominantly performed using the aerodynamic influence coefficient approach. The influence of the periodic boundaries and the recirculation channel is investigated. All simulations are performed on a modern turbocharger turbine and centrifugal compressor using ANSYS CFX V17.0 with an inhouse pre- and post-processing procedure at ABB Turbocharging. The comparison to experimental results concludes the paper.

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