Motor Inverter Current Sensor Fault Detection Without DC Sensing
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Solution Overview
Problem
Existing motor control devices face challenges in accurately detecting gain failures in AC current sensors without a DC current sensor, as AC and DC current estimation values become abnormal simultaneously when the AC current sensor fails, making it difficult to reduce the number of DC current sensors while ensuring reliable motor control.
Innovation Solution
A control device that calculates estimated DC current values using duty values and AC current sensor values from two phases, allowing for the determination of AC current sensor failures without a DC current sensor, by analyzing changes in these values and utilizing determination tables to identify failure phases and modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC current sensor is used for diagnostic purposes, then the reliability of failure detection is improved, but the cost and device complexity increase
Solution Approach 1:
The patent creates a virtual copy of the DC current sensor functionality by estimating DC current values from AC current sensor measurements and PWM duty ratios. This estimated DC current serves as a substitute for the physical DC current sensor, enabling failure detection without adding hardware complexity
Solution Approach 2:
The patent introduces an intermediary estimation mechanism that bridges the gap between AC current sensor data and DC current monitoring requirements. By using the PWM duty ratio as an intermediary parameter, the system can infer DC current conditions without direct measurement
2Device complexity
If DC current estimation is performed using AC current sensor values and duty ratios, then the number of sensors is reduced, but the accuracy of failure detection deteriorates when AC current sensor fails
Solution Approach 1:
The patent segments the failure detection process into multiple independent estimation calculations. By performing separate DC current estimations using different phase combinations and comparing results, the system can identify which specific sensor reading is abnormal, maintaining detection accuracy even with reduced hardware
Solution Approach 2:
The patent implements a feedback mechanism where the estimated DC current values are continuously monitored and compared against expected ranges. When discrepancies are detected, the system can identify sensor failures and provide feedback for corrective action, ensuring reliable failure detection without additional sensors
Data Source
AI summary
A failure phase of an AC current sensor is determined without providing a DC current sensor. A control device that controls a motor via an inverter circuit that supplies power converted from direct current to three-phase alternating current to the motor, in which a current sensor that detects alternating current of each phase of three-phase alternating current is provided at an output of the inverter circuit, and the control device calculates estimated DC current values by using a duty value of a PWM signal for controlling switching of the inverter circuit and an AC current value of two phases among three phases detected by the current sensor, and determines a failure of the current sensor on the basis of a change in the estimated DC current values that have been calculated.