Active Fault Detection Circuit for Refrigeration Current Leakage
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Solution Overview
Problem
Current passive protection technologies in transport refrigeration units fail to properly respond to certain conditions, posing safety concerns due to inadequate detection of current overload and leakage, which can lead to operational issues and quality control problems.
Innovation Solution
An active fault detection circuit using a microcontroller to measure line currents and voltage, controlling switches to manage power transmission and detect current overload and leakage, ensuring correct operation and safety by comparing actual and expected switch states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive protection technologies (circuit breakers) are used, then device complexity is reduced, but reliability of fault detection deteriorates due to inadequate response under certain conditions
Solution Approach 1:
The patent replaces passive mechanical circuit breakers with an active electronic fault detection system using a microcontroller that electronically monitors current and voltage conditions. This substitution enables intelligent decision-making through software logic (if-current-exceeds-threshold-then-open-switch) rather than relying solely on mechanical trip mechanisms, thereby improving detection reliability while maintaining acceptable complexity levels.
Solution Approach 2:
The system continuously monitors current and voltage conditions and uses this feedback to dynamically control the switch state. The microcontroller reads sensor data, compares it against predefined thresholds, and adjusts the switch accordingly. This closed-loop feedback mechanism ensures reliable fault detection and response, addressing the reliability weakness of passive protection systems.
2Reliability
If active fault detection circuit with microcontroller is implemented, then reliability of fault detection is improved, but device complexity increases due to additional components and control logic
Solution Approach 1:
The microcontroller serves multiple functions: it monitors current, monitors voltage, determines operational mode (run or start), controls the switch, and validates switch operation. By consolidating these functions into a single multi-functional component, the patent reduces overall system complexity despite the increased capabilities, as the microcontroller replaces what would otherwise require multiple separate components and circuits.
Solution Approach 2:
The patent combines the fault detection logic, switch control, and switch validation functions into a single integrated circuit system. The microcontroller and its associated components are merged into one cohesive unit that performs all protection functions, reducing the number of discrete components and simplifying the overall system architecture while maintaining high reliability.
3Reliability
If switch validation is performed by comparing present state to expected state, then reliability is further improved, but device complexity and processing requirements increase
Solution Approach 1:
The system performs self-validation by automatically comparing the actual switch state against the expected state that should result from the current operational conditions. The microcontroller independently verifies its own control actions, creating a self-checking system that enhances reliability without requiring external validation mechanisms or additional hardware components.
Solution Approach 2:
The system pre-determines what the switch state should be based on the operational mode and sensor readings before actually executing the switch control. This preliminary calculation of expected state allows for validation against the actual state, creating a predictive check that prevents erroneous switch operations and improves reliability through advance verification.
Data Source
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AI summary
A system and method for detecting current overload and leakage in a transport refrigeration unit. The method comprises measuring, by a microcontroller of an active fault detection circuit, a line current for each of one or more phases supplying power to a load of a refrigerant vapor compression system of the transport refrigeration unit; measuring, by the microcontroller, a voltage received by the active fault detection circuit from a battery of the transport refrigeration unit and transmitted via a conductor of the active fault detection circuit to a microprocessor of the refrigerant vapor compression system; controlling, by the microcontroller, a switch along the conductor of the active fault detection circuit to control transmission of the voltage, via the conductor to the microprocessor, Controlling the switch comprises (i) closing the switch upon a determination that the voltage level is greater than or equal to an operational threshold voltage level, (ii) closing the switch upon a determination that the voltage level is less than the operational threshold voltage level, and (iii) opening the switch upon a determination that any of the one or more line currents exceeds a threshold. Other embodiments are described herein.