Multiphase Inverter Neutral Point Switching for Fault Tolerance
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Solution Overview
Problem
Existing rotary electric systems with multiphase inverters face challenges in reliably addressing open faults in high-side or low-side switching elements without complicating the circuit structure, leading to increased torque ripples and reduced drivability in multiphase motors.
Innovation Solution
A rotary electric system that includes a controller to selectively switch between full-wave and half-wave driving modes by connecting a switch member between the neutral point and either the high-side or low-side electrodes, allowing continuous operation even if one high-side switching element fails, thereby reducing current unbalance and torque ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If individual relays are added for each phase stator winding to address open faults, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple relay functions into a single relay that can selectively connect or disconnect any phase stator winding. Instead of having separate relays for each phase (U-phase, V-phase, W-phase), one relay is designed to handle all phases by selectively connecting the neutral point to different phases, thereby reducing device complexity while maintaining fault addressing capability
Solution Approach 2:
The relay is designed with multi-functionality to serve multiple purposes: it can disconnect faulty phases, connect healthy phases to the neutral point, and enable half-wave driving mode. This universal relay replaces what would traditionally require multiple specialized relays, reducing overall circuit complexity while improving reliability
2Reliability
If two-phase stator winding driving method is used to address switching element failure, then reliability is improved, but torque ripples increase
Solution Approach 1:
The system dynamically switches between full-wave driving mode (using all three phases) and half-wave driving mode (using only healthy phases) based on fault detection. When a switching element failure is detected, the relay selectively disconnects the faulty phase and connects only healthy phases to the neutral point, enabling dynamic adaptation that maintains continuous operation while minimizing torque ripples by optimizing the driving mode
Data Source
AI summary
In a rotary electric system, a switch member includes at least one of a first switch and a second switch. The first switch is connected between a neutral point of multiphase stator windings and a high-side electrode of a direct current power source. The second switch is connected between the neutral point and a low-side electrode of the direct current power source. A controller works to turn the switch member off and on thereby switching control of the multiphase inverter between full-wave driving mode and half-wave driving mode. The full-wave driving mode allows the controller to drive all of the high-side and low-side switching elements per phase of the multiphase stator windings. The half-wave driving mode allows the controller to drive any one of the high-side switching element and the low-side switching element per phase of the multiphase stator windings.