Motor Drive Electronics Fault Isolation via Phase Current Analysis
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Solution Overview
Problem
In pulse width modulated three-phase motor systems, it is challenging to accurately identify and isolate motor coil shorts and opens in the harnessing and motor from faults within the controlling circuitry, as current sensing circuitry typically does not provide sufficient information for component isolation.
Innovation Solution
A method and system that apply excitations to different phases of the electric motor, measure phase current values, and repeat the process for all possible combinations to isolate faults, using sourcing and sinking switching devices, and analyzing current values to determine fault locations, including identifying failures in motor drive electronics components without additional external test equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sensing circuitry is used for closed loop operation, then motor control functionality is achieved, but fault isolation capability is insufficient
Solution Approach 1:
The system performs preliminary diagnostic actions by applying test excitations to motor phases before normal operation to proactively identify faults. The MDE component applies excitation signals to each phase combination and records current responses, creating a baseline of expected behavior that enables future fault isolation without requiring additional external test equipment during actual operation.
Solution Approach 2:
The system uses current sensing circuitry to provide feedback on phase currents during both normal operation and diagnostic testing. By comparing the feedback current measurements from test excitations against expected values, the system can isolate faults in the motor, harnessing, or MDE component itself, transforming the existing feedback mechanism into a dual-purpose tool for both control and diagnostics.
2Measurement precision
If additional external test equipment is used for fault isolation, then diagnostic accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The MDE component is designed to perform multiple functions: it serves as both the motor drive controller during normal operation and as a self-contained diagnostic test system. The existing current sensing circuitry and switching devices are reused for both motor control and fault isolation testing, eliminating the need for separate external test equipment and reducing overall system complexity while maintaining diagnostic accuracy.
Solution Approach 2:
The motor drive electronics component performs self-diagnostics by applying test excitations to its own output phases and measuring the resulting currents through its existing sensing circuitry. This self-service capability allows the system to isolate faults within itself without requiring external testing equipment, reducing complexity while maintaining the ability to accurately identify failures in the motor, harnessing, or control circuitry.
Data Source
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Figure 3A~3B
AI summary
A system and a method of isolating a fault in an electric motor system having a motor drive electronics (MDE) component (210) that is configured to drive an electric motor (130) with a plurality of phases, the MDE executing a method of isolating the fault that includes applying an excitation to a first phase and a second phase of the electric motor (130) in a first direction and sensing a phase current value for each phase phases of the electric motor (130). The method also includes providing an excitation, for the first and second phase in an opposite direction of the first direction and measuring a phase current value for each phase. The applying, sensing, providing and measuring is repeated for every possible combination of phases of the electric motor. Finally, the method includes isolating the fault within the electric motor system based on the sensed and measured current values.