Current Sensor Failure Detection in Three-Phase Machines
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Solution Overview
Problem
Existing methods for detecting failed current sensors in three-phase machines are costly, complex, and prone to errors, leading to incorrect identification of faulty sensors and potential motor control issues, with a lack of efficient strategies for requalifying sensors that have recovered from failure.
Innovation Solution
A method and system that detect failed current sensors by determining if the absolute sum of phase currents is below an open circuit value, identifying approximately zero phase currents, and estimating a phase current value to balance the sum, using a controller to manage the detection and estimation process, thereby reducing the need for extensive components and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sensor control strategies are used to detect sensor failure by summing detected currents and comparing against estimate values, then sensor failure detection capability is provided, but the system becomes costly and complex requiring multiple sensors and extensive processing
Solution Approach 1:
The patent extracts only the essential detection logic needed for sensor failure detection. Instead of implementing full backup detection schemes with multiple sensors and extensive processing, the invention isolates the core function by simply summing the detected phase currents and comparing the absolute value against a predetermined threshold, eliminating unnecessary system complexity while maintaining detection capability
Solution Approach 2:
The patent inverts the conventional approach by not trying to detect sensor failure through complex comparison of detected currents against estimated values. Instead, it uses a straightforward threshold comparison of the summed current absolute value, simplifying the detection mechanism while maintaining effectiveness
2Measurement precision
If precision sensors are deployed for each phase to ensure accurate current detection, then measurement precision is improved, but the cost and device complexity increase
Solution Approach 1:
The patent makes the existing current sensors multi-functional by using them not only for normal current measurement but also for failure detection through the summation method. This eliminates the need for additional precision sensors or backup sensors, as the same sensors serve dual purposes, reducing both cost and device complexity while maintaining measurement precision
Solution Approach 2:
The system uses its own existing sensors to detect their own failures through the summation method. The current sensors continue to measure phase currents for motor control while simultaneously providing failure detection capability through the simple threshold comparison, making the system self-diagnostic without requiring external detection devices
3Reliability
If conventional detection methods with predetermined maximum current error values are used, then sensor failure can be detected, but small errors cause estimate drift leading to incorrect failure identification
Solution Approach 1:
The patent changes the detection parameter from comparing detected currents against estimated values with predetermined error margins to comparing the absolute value of summed currents against a predetermined threshold. This parameter change makes the detection method insensitive to small measurement errors and estimate drift, as the threshold comparison approach does not rely on accurate current estimates, thereby preventing incorrect failure identification
Data Source
AI summary
A method of detecting one or more failed current sensor and estimating a phase current for the failed current sensor on a three-phase machine is disclosed. The method may include detecting one or more failed current sensor by determining if an absolute value of a sum of the phase currents of the motor is below an open circuit value. The method may also include determining which phase currents are approximately zero, for each phase current associated with each phase of the motor, if the sum of the phase currents of the motor is not below the open circuit value. The method may further include estimating the phase current for the failed current sensor by determining the phase current value for the failed current sensor, that when added to the phase currents of the remaining current sensors, will make the sum of all the phase currents equal to approximately zero.