Synchronous Generator Short-Circuit Test Apparatus
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Solution Overview
Problem
The existing methods for performing instantaneous short-circuit tests on polyphase synchronous generators are inaccurate due to manual operation of the switch, leading to variability in rotation speed and synchronization with test voltages, which affects the reliability of measured circuit parameters.
Innovation Solution
An apparatus comprising an electromechanical medium voltage switch controlled by a unit that synchronizes the switch closure with the generator's voltage peaks, ensuring precise rotation speed matching and accurate short-circuit conditions, including a control unit, voltage and current measurement stages, and a recording device to measure transient currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual operation of the switch is used to perform instantaneous short-circuit tests, then the operation is simple and easy to perform, but the rotation speed and synchronization with test voltages become inaccurate and variable
Solution Approach 1:
The patent replaces manual mechanical switch operation with an automated control system that uses electronic switching devices (such as thyristors or transistors) controlled by a microprocessor or programmable logic controller. This substitution eliminates human reaction time variability and enables precise synchronization of switch closure with voltage peaks through electronic timing circuits that detect voltage zero-crossings or peak positions, thereby achieving accurate rotation speed matching and voltage synchronization while maintaining operational simplicity through automated control interfaces.
2Strength
If a medium voltage switch is used to withstand strong currents and electrodynamic stresses, then the switch can handle the short-circuit conditions, but the device complexity increases
Solution Approach 1:
The patent divides the switching function into multiple stages: a pre-switch that closes before the main medium voltage switch, allowing the main switch to operate under reduced stress conditions. The measurement system is also segmented into separate channels for voltage and current measurements with dedicated signal conditioning circuits for each phase, reducing the complexity of any single measurement path while maintaining overall system capability to handle strong currents and electrodynamic stresses.
Solution Approach 2:
The patent introduces intermediate measurement circuits and signal conditioning stages between the high-power switch and the measurement instrumentation. These intermediary devices include current transformers, voltage dividers, and signal amplifiers that isolate the sensitive measurement equipment from the high-stress electrical environment, allowing the medium voltage switch to withstand strong currents while protecting the measurement system from damage and reducing overall device complexity.
3Speed
If the prime mover is powered during short-circuit to maintain rotation speed, then nominal speed can be maintained, but torsional moments damage the mover and generator
Solution Approach 1:
The patent performs preliminary acceleration of the rotor to a speed slightly above nominal speed before initiating the short-circuit test. The prime mover is then disconnected before the short-circuit occurs, allowing the rotor to coast down naturally through inertia. The control system is designed to trigger the short-circuit at the optimal moment during this coast-down phase when the rotation speed is still sufficiently close to nominal, eliminating torsional moments while maintaining adequate speed for accurate measurement of synchronous generator parameters.
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 enables repeatable and accurate measurement of circuit parameters by ensuring optimal rotation speed and synchronized switch closure, enhancing the reliability and precision of short-circuit tests.
Implementation Method 1
the rotor is set to nominal rotation speed in the presence of an excitation current, so that a triad of symmetrical three-phase voltages is present at the terminals of the generator. When the test conditions are achieved, an instantaneous short-circuit is caused between the terminals of the generator by closing a dedicated switch.
Data Source
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AI summary
An apparatus for performing instantaneous short- circuit tests on polyphase synchronous generators includes : a switch (5) having first terminals (5a, 5b, 5c) connected to respective stator terminals (2a, 2b, 2c) of an electric generator (2) and second terminals (5d, Se, 5f) connected to one another; an acquisition module ( 18 ), configured to acquire electric signals (VR', VS', VT' ) representative of output voltages (VR,VS, VT) on the stator terminals (2a, 2b, 2c) of the electric generator (2), respectively; and a processing module (20), configured to cause the switch (5) to close as a function of the output voltages (VR, VS, VT) of the electric generator (2).