Contactor Failure Detection During Filter Capacitor Charging
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Solution Overview
Problem
Existing power conversion apparatuses in electric railway vehicles cannot determine failures in contactors after the start of charging the filter capacitor, as they rely on voltage threshold detection which may be delayed or incorrect due to contactor failures.
Innovation Solution
A power conversion apparatus with a contactor controller, failure determiner, and voltage measurers that monitor the contactor state and voltage variations over a preset period to determine contactor failures, ensuring accurate detection even after charging begins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the threshold voltage is set at a sufficiently small value to shorten the determination period, then the productivity is improved, but the reliability deteriorates because failures occurring after voltage increase cannot be detected
Solution Approach 1:
The patent applies preliminary action by performing failure determination during the charging period before the voltage reaches the threshold. The controller determines whether a failure has occurred by monitoring if the voltage increase rate falls below a predetermined threshold during the charging process, enabling detection of contactor failures that would occur after traditional threshold-based detection concludes.
2Measurement precision
If the power conversion apparatus determines charging based on voltage threshold arrival, then the measurement precision is improved, but the reliability worsens as it cannot detect failures after charging starts
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage increase rate during the charging period and comparing it against a predetermined threshold. The controller receives feedback about the charging status and uses this information to determine whether a contactor failure has occurred, creating a closed-loop detection system that operates throughout the entire charging process rather than only at the threshold arrival point.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables timely and accurate determination of contactor failures by assessing the contactor's closed state and voltage variations, preventing misinterpretation of voltage changes caused by external factors, thus ensuring reliable power conversion.
Implementation Method 1
a filter capacitor connected to the primary terminals of the inverter and configured to be charged with electric power fed from the power source
Implementation Method 2
a first voltage measurer to measure a first voltage value that is a value of a voltage between the terminals of the filter capacitor
Data Source
AI summary
A power conversion apparatus includes a filter capacitor, a contactor to electrically connect the filter capacitor to a power source or electrically disconnect the filter capacitor from the power source, and a failure determiner to determine whether a failure occurs in the contactor. When the contactor is kept closed during a determination period since closing of the contactor and a reduction in the voltage in the filter capacitor during the determination period is greater than or equal to a reference value, the failure determiner determines occurrence of a failure in the contactor.