Motor Driver Phase Loss Detection via Current Monitoring
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Solution Overview
Problem
Existing phase-loss detection methods for motor drivers are limited as they require closed-loop control and only detect phase loss before motor operation, failing to address phase loss conditions after startup and not applicable to motors without accurate current control.
Innovation Solution
A method using an OPHL detection module implemented via firmware, comprising logic, sample-and-hold, low-pass filter, and comparison units to detect direct-current and alternating-current phase loss before and after motor operation, allowing for single-phase and multi-phase detection without precise current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current vector control is used to detect phase loss before motor startup, then phase loss detection accuracy is improved, but the method becomes inapplicable to motors without closed-loop control
Solution Approach 1:
The patent changes the detection parameter from current vector (requiring closed-loop control) to phase current magnitude and voltage command state (applicable to open-loop and closed-loop systems). By monitoring whether phase current remains zero when voltage is applied, the system achieves universal applicability across different motor control types while maintaining detection accuracy
Solution Approach 2:
The patent replaces the complex closed-loop current vector control mechanism with a simpler open-loop detection approach using basic current sensing and logic operations. This substitution eliminates the requirement for accurate current control while preserving phase loss detection capability
2Device complexity
If phase loss detection is executed only before motor startup, then detection simplicity is improved, but phase loss conditions after startup cannot be detected
Solution Approach 1:
The patent implements continuous phase loss detection that operates both before and during motor startup by continuously monitoring phase current and voltage command states. The detection logic runs in real-time during motor operation, ensuring continuous safety monitoring without interrupting the useful action of motor control
Solution Approach 2:
The patent performs preliminary phase loss detection before motor startup by checking if phase current is zero when voltage command is applied. This preliminary action prevents startup under phase loss conditions, and the same detection logic continues to operate during runtime for ongoing protection
Data Source
AI summary
A method of detecting an output phase loss (OPHL) for a motor drive detects an abnormal OPHL operation when at least one phase of a three-phase current is continually zero. Each phase of the three-phase current is acquired, sampled, filtered, and compared. Hence, a corresponding zero-current counter value is continually added, and a corresponding abnormal current value is set as logic 1 when a zero-phase current of the three-phase current is continually zero. Finally, an OPHL certified value is set as logic 1 to confirm that the motor driver is operated in the abnormal OPHL operation. Therefore, a direct-current and an alternating-current OPHL can be detected before and after the motor driver is operated, respectively.