Electric Motor Control Apparatus Abnormal Phase Disconnect
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Solution Overview
Problem
Existing electric motor control systems fail to effectively manage abnormal states such as grounding or short-circuiting in multiphase electric motors or inverters, leading to torque pulsation and operational inefficiencies, as they either rely on hardware devices that increase size and cost or merely suppress overcurrent without improving motor operation.
Innovation Solution
An electric motor control apparatus with a current detecting circuit, current control means, switching element driving circuit, and inverter configuration that includes abnormal-state determining and disconnecting mechanisms to alter current control methods based on detected abnormal states, allowing continued operation and reduced torque pulsation by disconnecting affected phases and generating voltage commands suited to abnormal states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuses are added to blow out in abnormal states, then overcurrent protection is achieved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical fuse-based protection with an electronic control system that uses switching elements to disconnect abnormal phases. The controller detects abnormal states and commands switching elements to open circuits in affected phases, eliminating the need for physical fuses while achieving the same protective function through electronic means.
Solution Approach 2:
The patent introduces switching elements as intermediary components between the power source and motor phases. These switching elements act as controllable intermediaries that can be commanded to open or close circuits based on abnormal state detection, providing flexible protection without requiring permanent hardware additions like fuses.
2Reliability
If duties are limited to suppress overcurrent, then overcurrent is prevented, but torque pulsation increases
Solution Approach 1:
The patent segments the control strategy into normal-state control and abnormal-state control modes. In abnormal states, it selectively disconnects only the affected phases while maintaining control over healthy phases, allowing for optimized current distribution that reduces torque pulsation compared to uniform duty limitation across all phases.
Solution Approach 2:
The patent dynamically changes control parameters based on detected abnormal states. It adjusts voltage commands and current distribution strategies specifically for abnormal phases versus healthy phases, optimizing torque output and reducing pulsation by adapting control parameters to the specific abnormal condition rather than applying uniform limitation.
3Reliability
If switching elements are driven with limited duties, then overcurrent is suppressed, but short-circuiting paths may form due to response delays
Solution Approach 1:
The patent implements preliminary protection by having the controller detect abnormal states and immediately command switching elements to disconnect affected phases before dangerous current levels can develop. This proactive approach prevents short-circuiting paths from forming by establishing protective disconnection before response delays could allow hazardous conditions to arise.
Data Source
AI summary
A control apparatus for a multiphase AC electric motor having an inverter includes a current control including an abnormal-state current controller; an abnormal-state detector that detects an abnormal state of any of a wire of an electric motor, a wire of an inverter, and a wire connecting the electric motor to the inverter as an abnormal phase; and an abnormal phase disconnect. The abnormal phase disconnect disconnects one or more of phases detected to be in an abnormal-state and the abnormal-state current controller generates an abnormal state voltage command in accordance with detection of an abnormal state, and uses phases other than the disconnected phases of the inverter to control individual currents of the phases, with the abnormal-state voltage command used as a multiphase voltage command.