Three-Phase Motor Cable Anomaly Detection via Test Current Pulse
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Solution Overview
Problem
Existing electrified vehicle systems, such as hybrid-electric and all-electric vehicles, fail to detect anomalies in single-phase AC cables or current sensors, as high voltage interlock systems primarily monitor DC circuits and do not account for AC connections, leading to potential disconnections or loose connections going undetected.
Innovation Solution
A controller is programmed to inject a test d-axis current pulse into a three-phase electric machine, applying a position offset to the rotor measurement to ensure non-zero current magnitude at specific rotational positions, generating a diagnostic signal if any current sensor signal falls below a threshold, thus detecting anomalies in single-phase cables or current sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If high voltage interlock system monitors only DC circuits, then system complexity is reduced, but AC cable and current sensor anomaly detection capability is lost
Solution Approach 1:
The controller performs multiple functions: it controls the inverter to convert DC to three-phase AC power, monitors current through current sensors, and detects anomalies in AC cables and sensors. By making the controller multi-functional, the system avoids adding separate monitoring hardware while gaining comprehensive diagnostic capability.
Solution Approach 2:
The system continuously monitors current during normal operation and during specific rotational positions where phase current should be zero. By performing preliminary monitoring actions and comparing actual current against expected values, the system detects anomalies before they cause system failure.
2Reliability
If current monitoring is performed at all rotational positions, then anomaly detection capability is improved, but energy consumption increases
Solution Approach 1:
Instead of continuously monitoring at all rotational positions, the system performs anomaly detection at specific periodic intervals when the rotor reaches predetermined positions where phase current should be zero. This periodic monitoring approach maintains detection capability while minimizing energy consumption by activating monitoring only when needed.
Solution Approach 2:
The system applies a position offset to generate non-zero current at specific rotational positions, creating a test condition that exceeds normal operating requirements. This partial excessive action ensures detectable current flow for anomaly detection only when necessary, rather than maintaining elevated monitoring at all times.
3Productivity
If test current pulse exceeds maximum current threshold, then vehicle motion is initiated, but diagnostic accuracy for cable anomalies is reduced
Solution Approach 1:
The system applies a test current pulse that is carefully calibrated to exceed the minimum detectable current threshold for anomaly detection but remains below the maximum threshold that would initiate vehicle motion. This partial action achieves diagnostic testing without causing unwanted side effects.
Solution Approach 2:
The system changes the current parameter by injecting test pulses at specific rotational positions where the expected current is zero or minimal. By timing the test current injection with the rotor position, the system creates detectable current signals for diagnosis while maintaining control over the magnitude to prevent vehicle motion.
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 approach enables the detection of disconnections or anomalous operations in single AC cables or current sensors, improving the reliability of electric propulsion systems by generating a diagnostic signal for alerting operators and service personnel, thereby preventing system failures.
Implementation Method 1
an inverter coupled to the traction battery and operable to convert direct current (DC) power from the traction battery to three-phase alternating current (AC) power
Implementation Method 2
command the inverter to inject a test d-axis current pulse to the electric machine
Implementation Method 3
a current sensor associated with each cable/phase of the three-phase electric machine
Data Source
AI summary
An electrified vehicle includes a traction battery, an inverter coupled to the traction battery and operable to convert direct current (DC) power from the traction battery to three-phase alternating current (AC) power, a three-phase electric machine coupled to the inverter by associated cables, a sensor configured to generate a signal associated with rotational position of a rotor of the three-phase electric machine, a current sensor associated with each cable/phase of the three-phase electric machine, and a controller programmed to generate non-zero phase current at each of a plurality of predetermined regularly spaced rotational positions by either adjusting rotor angle or injecting q-axis current, command the inverter to inject a test current pulse to the electric machine, and generate a diagnostic signal in response to any one of the current sensor signals being less than an associated threshold to detect a cable or current sensor anomaly in a single phase.