Low-Voltage Protection Device Using Miller Effect Feedback
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Solution Overview
Problem
Conventional low-voltage protective devices experience late interruption of short-circuit currents due to uncertainties in the opening behavior of mechanical bypass switches, leading to increased load on the network and semiconductor circuit arrangements.
Innovation Solution
The implementation of a low-voltage protective device that utilizes the Miller effect-induced voltage spike to accurately detect the opening of the bypass switch contacts, allowing for precise timing in the activation of the semiconductor circuit arrangement to quickly interrupt the short-circuit current, thereby minimizing network and semiconductor load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bypass switch is activated electrically with a timer and safety factors to ensure sufficient opening, then the reliability of current interruption is improved, but the interruption time is delayed and the load on the network and semiconductor circuit arrangement is increased
Solution Approach 1:
The patent employs feedback by detecting the actual opening state of the bypass switch contacts through voltage measurement arrangements that monitor the voltage across the contacts. This real-time feedback allows the control unit to determine when the contacts are sufficiently opened and to trigger the semiconductor circuit arrangement at the optimal moment, eliminating the need for conservative timing margins while ensuring reliable current interruption.
Solution Approach 2:
The patent replaces the mechanical timer-based delay system with an electronic detection and control system. Instead of using mechanical switches and predetermined time delays, the system uses electronic voltage sensing and microcontroller-based logic to determine the exact moment when contact opening is sufficient, thereby substituting mechanical timing mechanisms with electronic control.
2Reliability
If the bypass switch contacts are opened wider and more slowly to ensure safe interruption, then the safety margin is increased, but the interruption speed is reduced and the short-circuit load is increased
Solution Approach 1:
The patent applies preliminary action by pre-positioning the semiconductor circuit arrangement in a ready state before the bypass switch contacts are fully opened. The control unit monitors the voltage across the contacts and, upon detecting that the voltage reaches a predetermined threshold indicating sufficient contact separation, immediately triggers the semiconductor circuit arrangement to interrupt the short-circuit current, thereby achieving both safety and speed.
Solution Approach 2:
The system continuously monitors the voltage across the bypass switch contacts and uses this feedback to determine the precise moment when contact opening is sufficient. This real-time feedback mechanism allows the system to wait for the optimal moment rather than using fixed timing margins, thereby achieving fast interruption while maintaining adequate safety margins.
3Reliability
If safety factors are applied to account for variations in mechanical switch opening behavior, then the reliability of contact opening is improved, but the timing precision is reduced and the interruption is delayed
Solution Approach 1:
The patent uses feedback from voltage measurement arrangements that directly monitor the actual voltage across the bypass switch contacts. This measurement provides direct information about the actual contact opening state, eliminating the need for timing-based estimates or safety margins. The control unit triggers the semiconductor circuit arrangement when the measured voltage indicates sufficient contact separation, achieving both reliability and timing precision.
Solution Approach 2:
The patent replaces the mechanical timer and switch-based delay mechanism with an electronic voltage detection system. Instead of relying on mechanical timing components and predetermined delays, the system uses electronic voltage sensing and microcontroller-based logic to determine the exact moment when contact opening is sufficient, thereby achieving high timing precision while maintaining reliability.
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
This approach enables the precise detection of the time point for complete contact opening, allowing for earlier and more efficient interruption of short-circuit currents, reducing the load on the network and semiconductor circuit, and enabling the use of power semiconductors with lower maximum loads, which are smaller and have reduced internal resistance and loop inductance.
Implementation Method 1
at least one voltage measurement arrangement configured to detect a Miller effect-induced voltage spike at the at least one power semiconductor
Data Source
AI summary
A low-voltage protective device includes: at least one outer conductor path from an outer conductor power terminal of the low-voltage protective device to an outer conductor load terminal of the low-voltage protective device; a neutral conductor path from a neutral conductor terminal of the low-voltage protective device to a neutral conductor load terminal of the low-voltage protective device; a mechanical bypass switch arranged in the outer conductor path; a first semiconductor circuit arrangement connected in parallel to the mechanical bypass switch, the first semiconductor circuit arrangement having at least one power semiconductor, such as an IGBT, with a control terminal, such as a gate terminal; an electronic control unit; a current-measurement arrangement arranged in the outer conductor path, connected to the electronic control unit of the protective device; and at least one voltage measurement arrangement for detecting a Miller effect-induced voltage spike at the at least one power semiconductor.