Inverter Emergency Mode for Torque Control
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Solution Overview
Problem
Existing drive unit systems disconnect the electric machine from the inverter during errors, leading to loss of torque control and increased complexity, cost, and space requirements, as they rely on phase separation relays to prevent undesired torque production.
Innovation Solution
The drive unit operates the inverter in an emergency mode after an error occurs, maintaining electrical connection and allowing the electric machine to produce torque, eliminating the need for phase separation relays by using high-side and low-side switches with freewheeling paths and selecting appropriate emergency operating modes based on the error type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase separation relay is used to disconnect the electric machine from the inverter during errors, then the electric machine is prevented from producing undesired torque, but the device complexity, construction space, and costs increase
Solution Approach 1:
The invention extracts and eliminates the phase separation relay from the system by implementing emergency operating modes that directly control the inverter switches. The error handling functionality is integrated into the control unit, removing the need for separate separating devices while maintaining torque control during errors
Solution Approach 2:
The control unit is enhanced to provide multiple functions: normal operation control, error detection, and emergency operating mode management. This multi-functional approach consolidates the roles previously requiring separate components, reducing device complexity while maintaining reliability
2Reliability
If a phase separation relay is used to disconnect the electric machine from the inverter during errors, then the electric machine is prevented from producing undesired torque, but the construction space and costs increase
Solution Approach 1:
The phase separation relay and its associated mounting space are completely removed from the system. The control unit directly manages inverter operation during errors, eliminating the need for physical separating devices and reducing construction space requirements
3Productivity
If the inverter is operated in emergency operating mode after an error, then torque production is maintained, but the inverter must handle fault conditions
Solution Approach 1:
The control unit is designed with pre-programmed emergency operating modes that are prepared in advance for various error conditions. When errors occur, these pre-established modes enable immediate torque maintenance without requiring complex real-time decision-making, cushioning the system against fault impacts
Solution Approach 2:
The control unit continuously monitors inverter operation and switch states, using feedback from error detection to automatically transition between normal and emergency operating modes. This closed-loop control ensures the inverter adapts to fault conditions while maintaining torque production
Data Source
AI summary
In a method for operating a drive unit having an electric machine, in a normal operating mode the electric machine is operated with current provided by an inverter on at least two phases, and particular phase voltages for the electric machine are set on the phases. Upon an occurrence of an error of the inverter, the inverter is operated in an emergency operating mode for the further operation of the electric machine.