Current Sensor Self-Test via Test Coil Injection
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Solution Overview
Problem
Current sensors in high-voltage battery systems for motor vehicles lack a reliable self-test function to ensure accurate current measurement, which is crucial for safety but is economically unattractive due to redundancy and ambiguity in sensor validation.
Innovation Solution
A current sensor with a test current generator that modifies the magnetic field to verify the output variable, using a test current signal to check for proper functioning by comparing measured values within defined intervals, accounting for operating state changes and non-linearities, and incorporating a compensation winding for improved linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy through the use of several current sensors is implemented, then measurement reliability is improved, but system cost increases
Solution Approach 1:
The current sensor performs self-diagnosis by injecting a test current through the test winding and measuring the resulting change in output signal. This allows the sensor to verify its own functionality without requiring redundant sensors or external testing equipment, thereby maintaining reliability while avoiding additional system cost.
Solution Approach 2:
The sensor conducts preliminary self-tests periodically to detect potential failures before they affect critical measurements. The test current generator injects test currents at predetermined intervals to proactively identify sensor degradation or failure modes, ensuring reliability without needing multiple sensors.
2Reliability
If a self-test function is added to the current sensor, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The test winding serves multiple functions: it acts as both a testing component for self-diagnosis and as part of the magnetic core structure for normal current measurement. The same magnetic core and sensor element are used for both testing and measurement, avoiding the need for separate dedicated test hardware and minimizing added complexity.
Solution Approach 2:
The test current generator is integrated with the existing sensor electronics, sharing the same signal processing path and microcontroller. The test current is injected through the existing conductor or additional winding, and the resulting signal is processed through the existing amplifier and A/D converter, merging the test function with the measurement function to minimize additional complexity.
3Measurement precision
If test current injection is used to verify sensor output, then measurement accuracy is improved, but power consumption increases
Solution Approach 1:
The self-test function is executed periodically rather than continuously. The test current generator injects test currents at predetermined intervals or when triggered by specific events, allowing the sensor to verify accuracy only when needed while minimizing power consumption during normal operation.
Solution Approach 2:
The test current uses a predetermined, controlled amplitude that is sufficient to verify sensor functionality but does not require excessive current levels. The test current is designed to be just enough to produce a measurable change in the sensor output, avoiding unnecessary power consumption while maintaining measurement accuracy verification.
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 solution provides a reliable self-test mechanism for current sensors, ensuring accurate measurements and initiating safety measures when necessary, while minimizing power consumption and additional circuit complexity.
Implementation Method 1
A sensor element (22) is arranged on the core (21), which generates an output variable that is dependent on the magnetic field
Implementation Method 2
Measurement using transformers, based on the induction principle
Implementation Method 3
A test winding (23) with a number w p of turns is also arranged around the core (21) and is connected to a test current generator (24). The test winding (23) thus generates an additional magnetic field in the core (21)
Data Source
Figure 1
Figure 2
Figure 3a~3e
AI summary
The invention relates to a current sensor for measuring a current in a conductor (20) using a magnetic field generated by the current, said current sensor at least having a core (21) that is arranged around the conductor, a sensing element (22) which is arranged on the core and which is designed to generate an output variable dependent on a magnetic field in the core, and a measuring unit which is designed to detect the output variable and to derive a measured value of the current in the conductor from the detected output variable. The current sensor further has a test coil (23) that is arranged around the core, a test current generator (24) which is connected to the test coil and which is designed to generate a test current signal of a specified amplitude in response to a control signal and to output said test current signal to the test coil. The current sensor also has a testing unit (25) which is connected to the measuring unit and to the test current generator and which is designed to output information on whether the current sensor is functioning properly, said information being outputted as a test signal, dependent on a result of the comparison of a first and a second measured value.