Motor Current Detector Fault Detection With Dead Time Compensation
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Solution Overview
Problem
Existing motor control devices face challenges in detecting abnormalities in current detectors, particularly when the motor is stopped, leading to potential overcurrent and burnout due to increased dead time voltage errors and erroneous detections, especially in multi-motor systems.
Innovation Solution
A motor control device that calculates a voltage command threshold by adding a dead time voltage error to an ideal voltage command threshold, using current detection values and dead time compensation to determine abnormalities, preventing erroneous detections and prompt detection of current detector issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current detector abnormality detection is performed using three-phase sum method, then abnormality detection capability is improved, but device complexity and cost increase due to requiring current detectors on all power lines
Solution Approach 1:
The patent extracts the abnormality detection function from a system requiring multiple current detectors and implements it using only one current detector on a single power line. By taking out the essential detection capability and removing unnecessary components (other current detectors), the system achieves abnormality detection without increasing device complexity.
Solution Approach 2:
The patent makes a single current detector perform multiple functions: it detects both normal current values and abnormality conditions (such as open circuit or short circuit faults). By utilizing the voltage command value and current detection value relationship, the same detector serves dual purposes, eliminating the need for separate detectors on all power lines.
2Ease of operation
If dead time voltage error is not considered in abnormality detection threshold, then detection simplicity is improved, but measurement precision deteriorates leading to erroneous detections
Solution Approach 1:
The patent changes the detection threshold parameter from a fixed value to a dynamic value that accounts for dead time voltage error. By calculating the threshold as (voltage command value - dead time voltage error), the system adapts the threshold to actual operating conditions, improving measurement precision without significantly complicating the detection process.
3Reliability
If margin is set large to avoid erroneous detection, then reliability is improved, but detection responsiveness deteriorates as abnormalities cannot be promptly detected
Solution Approach 1:
The patent dynamically adjusts the detection threshold parameter based on the voltage command value and dead time voltage error calculation. This allows the system to maintain high reliability by accounting for error sources while achieving prompt detection, as the threshold is set precisely rather than using a conservative large margin that would delay detection.
4Device complexity
If current detector abnormality is not detected when motor is stopped, then system simplicity is maintained, but safety deteriorates due to potential overcurrent and burnout
Solution Approach 1:
The patent performs preliminary abnormality detection by checking the relationship between voltage command value and current detection value even when the motor is stopped. By conducting detection in advance before motor operation, the system identifies potential abnormalities that could lead to overcurrent and burnout, preventing harmful effects before they occur.
Solution Approach 2:
The patent implements a feedback mechanism where the abnormality determination unit continuously monitors the relationship between voltage command value and current detection value. This feedback loop detects abnormalities regardless of motor state (stopped or running), providing continuous safety monitoring without significantly increasing system complexity.
Data Source
AI summary
A motor control device includes an abnormality determination unit that determines the presence of any abnormality in a current detector. The abnormality determination unit includes, for example, a U-phase abnormality determination device. The U-phase abnormality determination device calculates, as a voltage command threshold, a value obtained by adding a dead time voltage error, which is a voltage error occurring due to a dead time, to an ideal voltage command threshold, which is a value obtained by multiplying a prescribed reference current value by a motor resistance value, and outputs a signal indicating an abnormality in the current detector when the effective value of a voltage command value is equal to or greater than the voltage command threshold and the effective value of a current detection value is equal to or less than a current detection threshold that is lower than the reference current value.