Wedge Tightness Determination in Dynamoelectric Machines
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Solution Overview
Problem
Conventional methods for inspecting the tightness of stator wedges in dynamoelectric machines are subjective, time-consuming, and inaccessible in many generators, posing a risk of catastrophic failure due to loose wedges causing stator coil vibration.
Innovation Solution
A system and method involving a force application device and a measuring device that apply a predetermined force radially to the wedge and measure its movement relative to adjacent core surfaces, allowing for accurate determination of wedge tightness without removing the rotor, using a bar jacking device and linear voltage displacement transducer, linked to a computer system for data processing and analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual tapping method is used to inspect stator wedge tightness, then the inspection can be performed without special equipment, but the measurement is extremely subjective and depends on technician experience
Solution Approach 1:
The patent replaces the subjective mechanical tapping method with an electrical measurement system. A measuring device with indicator contacts electrically connected to a display device provides objective numerical readings of wedge tightness, eliminating dependence on technician experience and subjective judgment while maintaining ease of inspection.
2Measurement precision
If depth gauge measurement through pre-formed test holes is used, then objective measurements can be obtained, but the method is time consuming and only possible in generators with pre-formed test holes
Solution Approach 1:
The patent extracts the measurement function from the complex depth gauge insertion process through pre-formed holes. The new measuring device places indicator contacts directly on the wedge surface, eliminating the need for test holes and reducing inspection time while maintaining objective measurement capability.
Solution Approach 2:
The patent introduces indicator contacts as intermediary elements that electrically connect the wedge surface to the display device. These contacts provide a new measurement pathway that is faster than depth gauge insertion and works on all generator types regardless of whether pre-formed test holes exist.
3Measurement precision
If depth gauge measurement through pre-formed test holes is used, then objective measurements can be obtained, but the method requires generators to be rewound with wedges having access holes
Solution Approach 1:
The patent removes the requirement for pre-formed test holes and wedge modifications. The measuring device uses indicator contacts that can be placed directly on the wedge surface, extracting the measurement capability from the modified wedge structure and making it applicable to all generator types without rewinding.
4Measurement precision
If the measuring device applies force to the wedge, then accurate tightness determination can be made, but the force application must be controlled to prevent wedge damage
Solution Approach 1:
The patent employs feedback control where the measuring device monitors the force applied to the wedge and adjusts accordingly. The display device shows real-time measurements, allowing the operator to stop before excessive force is applied, thus ensuring accurate tightness determination while protecting wedge structural integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides a reliable, non-invasive method to assess wedge tightness, identifying the force required to move the wedge, which indicates its tightness, enabling proactive maintenance to prevent vibration and failure, and can be applied to generators without pre-formed test holes.
Implementation Method 1
A measuring device for measuring movement of the wedge, measures a movement distance relative to a surface of an adjacent core surface
Implementation Method 2
a force application device for applying a predetermined force or a known quantity of force to a wedge, and the force is applied in a substantially radial direction
Data Source
AI summary
A system and method for determining wedge tightness in a dynamoelectric machine is provided. The dynamoelectric machine includes a rotor, stator and a wedge assembly having at least one wedge for retaining a coil. The system includes a force application device for applying a predetermined force or a known quantity of force to a wedge, and the force is applied in a substantially radial direction. A measuring device for measuring movement of the wedge, measures a movement distance relative to a surface of an adjacent core surface. The system can be inserted between the rotor and the stator, and the movement distance is obtained by evaluating a distance to an adjacent core surface and a distance to a surface of the wedge.