Generator Control Relay Test Circuit for Online Switch Integrity
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Solution Overview
Problem
Verifying the integrity of generator control relay circuitry in aerospace electrical power generation systems is difficult due to excitor current flowing through the circuit in steady state, making it challenging to detect failures in the generator control relay circuitry while the generating channel is online.
Innovation Solution
A continuous built-in test circuit for generator control relay switches, which includes a controller, GCR switch control circuit, and voltage monitoring circuit to periodically test the GCR switch operation by opening it when no current is flowing, measuring the voltage, and comparing it to a threshold to determine pass/fail conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the GCR switch control circuit opens the GCR switch for testing, then the test coverage is improved, but switching losses are introduced
Solution Approach 1:
The system performs continuous built-in tests periodically by opening the GCR switch only during designated test intervals rather than continuously. The controller receives test requests, determines appropriate test timing, and executes tests at periodic intervals, allowing the system to maintain test coverage while minimizing energy losses by keeping the switch closed during normal operation.
Solution Approach 2:
The system changes the operational state of the GCR switch from its normal closed state to an open state temporarily during test periods. By dynamically changing the switch state parameter based on test requirements rather than maintaining a fixed state, the system achieves test coverage while limiting switching losses to only the necessary test duration.
2Reliability
If the GCR switch is opened during steady state with current flowing, then the test can be performed, but it may impact the control loop and cause instability
Solution Approach 1:
The controller determines the appropriate timing for opening the GCR switch by evaluating control loop conditions before executing the test. The system performs preliminary assessment of whether the control loop can tolerate the switch opening, and only proceeds with the test when conditions are favorable, thereby maintaining control loop stability while enabling test execution.
3Reliability
If the GCR switch remains closed during operation, then the system provides continuous protection, but the switch integrity cannot be verified
Solution Approach 1:
The system performs self-diagnosis by continuously monitoring its own components. The voltage monitoring circuit measures the voltage across the GCR switch during normal operation and during test periods, allowing the system to self-verify switch integrity without external testing equipment. This enables the system to maintain continuous protection while periodically verifying switch health through built-in monitoring capabilities.
4Measurement precision
If voltage is monitored continuously across the GCR switch, then switch integrity can be detected, but energy consumption increases
Solution Approach 1:
The voltage monitoring circuit operates periodically rather than continuously, activating during test periods triggered by test requests and remaining inactive during normal operation. This periodic monitoring approach maintains the ability to detect switch integrity issues while significantly reducing energy consumption compared to continuous monitoring.
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
Ensures continuous test coverage of the GCR switch, detects dormant failure modes, and maintains safe operation by ensuring redundant protection without impacting the control loop or adding switching losses.
Implementation Method 1
a voltage monitoring circuit configured to monitor a voltage across the GCR switch when the GCR switch is opened
Implementation Method 2
compare the monitored voltage to a threshold value, generate a first output value indicating the GCR switch has passed the continuous built-in test responsive to a first comparison result
Data Source
AI summary
An apparatus may include a controller configured to periodically generate a control signal at a first logic level to initiate a continuous built-in test for a generator control relay (GCR) switch. The apparatus may also include a GCR switch control circuit configured to determine when the GCR switch will not have a current flowing therethrough and generate a GCR switch control signal to open the GCR switch responsive to the control signal. The apparatus may further include a voltage monitoring circuit configured to monitor a voltage across the GCR switch when the GCR switch is opened and compare the monitored voltage to a threshold value. The voltage monitoring circuit is also configured to generate a first output value indicating the GCR switch has passed the continuous built-in test or a second output value indicating the GCR switch has failed the continuous built-in test.