AC Motor Control Device Sensor Abnormality Detection
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Solution Overview
Problem
Existing control devices for AC motors face challenges in accurately detecting abnormalities in current sensors, particularly due to interference from current feedback and the need for high-speed sampling, which can lead to impaired detection accuracy and increased size and cost.
Innovation Solution
A control device for a three-phase AC motor that includes separate current sensors for control and monitoring phases, with a system that switches between monitoring stop and monitoring modes to prevent interference, allowing for accurate abnormality detection using estimated current values and enabling the use of fewer and less expensive sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If current sensors are used for both control and monitoring purposes, then device complexity is reduced, but measurement precision deteriorates due to current feedback interference
Solution Approach 1:
The patent divides the monitoring function into two distinct modes: a first monitoring mode that uses current sensors for abnormality detection without feedback interference, and a second monitoring mode that uses estimated current values. This segmentation allows the system to achieve accurate abnormality detection while reducing the number of physical current sensors needed.
Solution Approach 2:
The patent changes the parameter being monitored by switching between two different monitoring approaches: one that directly measures current using sensors, and another that monitors based on estimated current values calculated from motor parameters and control signals. This parameter change enables accurate monitoring with fewer sensors.
2Productivity
If high-speed sampling is performed for current feedback control, then control performance is improved, but abnormality detection accuracy deteriorates due to feedback interference
Solution Approach 1:
The patent implements periodic switching between the first monitoring mode (using current sensors) and the second monitoring mode (using estimated current values). This periodic action allows the system to perform high-speed current feedback control while periodically checking for sensor abnormalities using estimation-based monitoring that is free from feedback interference.
Solution Approach 2:
The patent introduces estimated current values as an intermediary for abnormality detection. These estimated values serve as a mediator that allows monitoring without being affected by the current feedback loop, enabling accurate abnormality detection while maintaining high-speed control performance.
3Device complexity
If current sensors are reduced in number, then cost and size are reduced, but reliability deteriorates due to inability to detect sensor abnormalities
Solution Approach 1:
The patent replaces direct mechanical/electrical measurement with a computational estimation approach. By using motor parameters, control signals, and mathematical models to estimate current values, the system can detect sensor abnormalities without relying solely on additional physical sensors, thereby maintaining reliability while reducing hardware complexity.
Data Source
AI summary
A control device for a three-phase alternate current motor, includes: a control phase current acquisition means; a monitor phase current acquisition means; a rotation angle acquisition means; a two-phase control current value current calculation means; a one-phase current estimated value estimation means; a voltage command value calculation means; an other phase current estimation means for calculating a monitor or a control phase current estimated value; an abnormality detection means for detecting an abnormality in a monitor phase or a control phase current sensor; and a switching means for switching between a monitoring stop mode, in which the voltage command value is calculated based on the two-phase control current value, and a monitoring mode, in which the voltage command value is calculated based on the one-phase current estimated value, and the abnormality detection means detects the abnormality, at predetermined time intervals.