Open Phase Fault Detection in Multi-Phase Electric Machines
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Solution Overview
Problem
Existing methods for detecting open phase faults in multi-phase electric machines, particularly in high-power applications like hybrid electric vehicles, are complex and require numerous hardware components, posing safety risks due to unpredictable torque behavior caused by overcurrents in two-phase motors when one phase is open.
Innovation Solution
A method that measures current values of each phase, calculates phase delays using cross-correlation coefficients, and applies a debouncing algorithm to detect if the phase delay exceeds a threshold, allowing for efficient detection of open phase faults with minimal hardware components and input parameters, thereby ensuring safety by transferring the system into a safe state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If detection circuits with many components are used to detect open phase faults, then detection capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential detection function from complex detection circuits by using only the existing current sensor signals that are already available in the motor control system. The open phase detection is achieved by processing the current signals Iu, Iv, and IW through coordinate transformation and phase difference calculation, eliminating the need for additional detection hardware components.
Solution Approach 2:
The existing current sensors, which are already installed for motor control purposes, are made multi-functional by also using them for open phase fault detection. The same current signals serve both motor control and fault detection functions, thereby avoiding additional hardware requirements.
2Measurement precision
If additional hardware components are added to improve detection accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses its own existing current measurement capabilities to perform self-diagnosis for open phase detection. The motor control system's built-in current sensors and processing units are leveraged to detect faults without requiring external or additional measurement devices.
Solution Approach 2:
The patent introduces mathematical transformations (coordinate transformation and phase difference calculation) as intermediaries to extract fault information from the existing current signals. These computational methods serve as mediators that enable precise fault detection without additional physical hardware.
Data Source
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AI summary
Method for detecting an open phase fault in a multi-phase electric machine, wherein the method (40) comprises the steps of: - measuring at least one current value of each phase of the multi-phase electric machine (41); - for always two phases of the multi-phase electric machine, determining a phase delay between the two phases based on the measured current values (42); - determining if a determined phase delay between two phases exceeds a predetermined threshold (43); - if a determined phase delay between two phases exceeds a predetermined threshold, detecting that there is an open phase fault (44).