Phase Current Sensor Fault Detection Beyond Linear Range
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Solution Overview
Problem
Current electric machine systems struggle to detect sensor-related faults when current sensors measure currents outside their linear ranges, leading to inaccurate measurements and potential system degradation.
Innovation Solution
A control system for a multi-phase electric machine that includes an inverter, phase current sensors, and a controller capable of monitoring and extrapolating current values using a current extrapolation routine, detecting faults by determining a zero-sum-shift parameter and comparing it with measured currents, thereby extending the sensing range and preventing false fail counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If current sensors operate outside their linear measurement range, then the electric machine can operate at higher current levels, but measurement accuracy deteriorates and sensor faults cannot be reliably detected
Solution Approach 1:
The patent introduces an intermediary calculation method that uses the relationship between multiple phase currents (where the sum should equal zero) to detect sensor faults. Instead of directly trusting the saturated sensor reading, the system calculates an expected current value based on the other phase sensors and compares it with the actual reading, using this intermediate comparison to identify faults even when operating outside the linear range
Solution Approach 2:
The system implements feedback by continuously monitoring the relationship between multiple phase current sensors and comparing measured values against expected values derived from the fundamental principle that phase currents sum to zero. This feedback mechanism allows the system to detect when a sensor has failed or is operating non-linearly, even at high current levels
2Reliability
If traditional fault detection methods are used, then the system can detect sensor faults within the linear range, but fault detection capability is lost when currents exceed the linear measurement range
Solution Approach 1:
The patent makes the fault detection system universal by designing a methodology that works across all operating conditions - both within and outside the linear measurement range. The same fault detection algorithm (comparing phase current relationships) applies regardless of current magnitude, making the system adaptable to the full range of operating conditions without requiring different detection methods for different ranges
3Force
If current sensors are used beyond their calibrated range, then the electric machine can deliver higher torque, but the signal output becomes non-linear and saturated
Solution Approach 1:
The system uses an intermediary calculation approach where the expected current value is derived from the relationship between multiple phase sensors rather than directly from the potentially saturated sensor reading. This intermediary calculation method allows the system to maintain accuracy and detect faults even when individual sensors operate beyond their linear range
Data Source
AI summary
The disclosure includes a control system for a multi-phase electric machine that includes an inverter configured to transfer electric energy from a rechargeable energy storage device (RESS), and phase current sensors. A controller includes an executable instruction set to monitor, via the phase current sensors, the phase currents, and detect that one of the phase currents is outside a linear measurement range of a respective one of the phase current sensors. An extrapolated current for the respective one of the phase current sensors is determined based upon the phase currents from others of the phase current sensors. A current extrapolation routine evaluates the respective one of the phase current sensors. A fault is detected in the respective one of the phase current sensors based upon the current extrapolation routine and the extrapolated current.