Ground Fault Protection Adjusting DC Link Voltage
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Solution Overview
Problem
Existing ground fault protection systems unnecessarily restrict power output to zero when leakage currents exceed a maximum limit, preventing the movement of electric machines under faulty conditions, which is undesirable in applications requiring machine operation during maintenance.
Innovation Solution
A system that determines a ground fault detection percentage value based on detected voltage and DC link voltage, calculates a worst-case component insulation voltage, and adjusts the DC link voltage to a new value based on the rated insulation voltage when the component is under stress, allowing the machine to operate safely and move to a workshop for repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power output is restricted to zero when ground leakage current exceeds the maximum limit, then the machine components are protected from damage, but the machine cannot be moved to a workshop for repair
Solution Approach 1:
The patent applies dynamics by making the DC link voltage adjustable rather than fixed. The controller dynamically modifies the DC link voltage based on the detected ground fault condition, allowing the system to adapt its operating parameters in real-time. This enables the machine to continue operating at reduced capacity rather than being completely shut down, thus maintaining mobility while still protecting components.
Solution Approach 2:
The patent changes the operating parameter (DC link voltage) in response to the ground fault condition. By calculating a modified DC link voltage based on the detected leakage current and original DC link voltage, the system adjusts its operational parameters to allow continued movement. This parameter change resolves the contradiction by enabling machine mobility while maintaining component protection through controlled operation.
2Reliability
If the DC link voltage is reduced to protect component insulation, then the machine can operate under ground fault conditions, but the power output is limited
Solution Approach 1:
The patent applies partial action by implementing a proportional response rather than a complete shutdown. The controller calculates a modified DC link voltage that is partially reduced from the original value, allowing the machine to operate at reduced power output rather than zero power. This partial action protects insulation while maintaining sufficient power for movement and basic operations.
Data Source
AI summary
A ground fault protection system may include a controller that is configured to receive signals representing a ground fault detection voltage and a DC link voltage of the machine. Based on the ground fault detection voltage and the DC link voltage, the controller may determine a ground fault detection percentage value, and a worst case component insulation voltage. The controller may compare an absolute value of the worst case component insulation voltage with a rated insulation voltage of a component of the machine. When the absolute value of the worst case component insulation voltage is higher than the rated insulation voltage, the controller may determine a new DC link voltage based on the rated insulation voltage and the ground fault detection percentage value, and may operate the machine by using the new DC link voltage.