Generator Stator Core Testing via Frequency-Converted Rotor Excitation
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Solution Overview
Problem
Current methods for testing the insulation condition of a generator's stator core, such as the loop test, are inefficient and costly due to the need to remove the rotor or block monitoring access, and provide limited information on insulation health, risking damage from overheating.
Innovation Solution
An apparatus and method using a frequency converter to increase the excitation current frequency, allowing the rotor to simulate a generator operation state without overheating, using a single excitation winding to test the stator core's temperature and insulation condition without removing the rotor, reducing costs and setup complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a loop test is conducted using excitation cables wrapped through the stator core, then the stator core temperature can be simulated, but the rotor must be removed which increases time and cost
Solution Approach 1:
The patent introduces an intermediary frequency converter device that converts 50Hz excitation current to higher frequency (e.g., 500Hz), enabling the rotor to function as an excitation winding without direct physical modification or removal. This intermediary frequency conversion mechanism allows the test to proceed with the rotor in place, resolving the contradiction between testing accuracy and time loss.
2Temperature
If excitation current frequency is increased to simulate generator operation state, then stator core temperature increases for better testing, but rotor may overheat
Solution Approach 1:
The patent changes the frequency parameter of the excitation current from 50Hz to higher frequencies (e.g., 500Hz). This parameter change allows the stator core to reach sufficient testing temperatures while the higher frequency reduces the current magnitude required, thereby limiting rotor heating and preventing overheating damage.
3Ease of manufacture
If ELCID is used to test stator core insulation, then the testing is economical, but only limited information on insulation condition is provided
Solution Approach 1:
The patent merges the advantages of ELCID (economic feasibility) with the comprehensive temperature monitoring capability of loop tests. By using frequency-converted excitation current applied to the rotor while monitoring stator core temperature, the method combines cost-effectiveness with complete insulation condition information, resolving the contradiction between testing cost and information completeness.
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 allows for efficient and reliable testing of the stator core's insulation condition, simulating a near-normal operation state with reduced power and equipment size, minimizing overheating risks and setup time, while providing comprehensive temperature monitoring.
Implementation Method 1
The frequency convertor is configured to convert the base frequency of the excitation current to an excitation frequency that is greater than the base frequency
Implementation Method 2
A rotating magnetic flux may be produced by the rotor winding rotating within the stator core, which cuts stator windings and generates alternating current within the stator windings
Implementation Method 3
If a number of laminations short together such that a loop can be established around the magnetic flux, then current will flow in that loop generating heat
Implementation Method 4
A damaged insulation of stator core may result in higher eddy current and a higher local temperature, also known as a local hot spot, between several laminations
Data Source
AI summary
An apparatus and a method for testing a stator core of a generator are presented. The apparatus includes a power supply. The power supply provides an excitation current having a base frequency. A frequency convertor is connected to the power supply. The frequency convertor converts the base frequency of the excitation current to an excitation frequency that is greater than the base frequency. An excitation cable connects the frequency convertor to a rotor at two axial ends. The rotor is excited by the excitation current with the excitation frequency as a single excitation winding for simulating an operation state of the generator causing hot spots on the stator core without overheating the rotor.