Solid-State Circuit Breaker Interlocking for Short-Circuit Failure Isolation

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Solution Overview

Problem

Solid-state circuit breakers face challenges when a short circuit failure occurs, as they are unable to open, potentially leading to detrimental consequences for the circuit interruption system and load.

Innovation Solution

A system where a first solid-state circuit breaker detects a failure mode and requests an upstream circuit breaker to interrupt current, allowing the first circuit breaker to open its mechanical contacts when the current drops to a predetermined level, ensuring safe operation and minimizing disruption to other loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a solid state circuit breaker uses a semiconductor device to interrupt current, then the interruption speed and size are improved, but the reliability deteriorates when the semiconductor device fails in a short circuit mode

Engineering Contradiction:

Improveinterruption speedVSAvoidreliability under short circuit failure

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The circuit breaker is segmented into two functional parts: a solid state switch for normal operation and a mechanical contact system for failure mode handling. The solid state portion provides fast interruption under normal conditions, while the mechanical portion provides reliable interruption when the solid state device fails, thus resolving the contradiction between speed and reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mechanical contact system is pre-positioned and ready to activate when a short circuit failure is detected. The system performs preliminary preparation by having the mechanical contacts in a ready state, so that upon detection of solid state failure, the mechanical contacts can immediately take over to interrupt the current, ensuring reliability without sacrificing normal operation speed.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If an upstream circuit breaker interrupts current to allow the solid state circuit breaker to open mechanical contacts, then the safety is improved, but the disruption to other loads increases

Engineering Contradiction:

Improvesafety during failure modeVSAvoiddisruption to other loads

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The failure mode handling function is extracted from the solid state circuit breaker itself and assigned to the upstream circuit breaker. When a short circuit failure occurs, the upstream breaker is selectively activated to interrupt current only for the affected downstream circuit, while other circuits remain unaffected. This extraction allows safe failure handling while minimizing disruption to other loads.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The upstream circuit breaker acts as an intermediary that mediates between the failed solid state circuit breaker and the power source. It temporarily assumes control of current interruption for the affected circuit, allowing the mechanical contacts to open safely, then releases control once the failure is resolved. This intermediary role ensures safety while limiting the scope of disruption.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Volume of moving object

If the solid state circuit breaker uses a smaller air gap, then the size is reduced, but the ability to provide galvanic isolation deteriorates when the semiconductor device fails

Engineering Contradiction:

Improveair gap sizeVSAvoidgalvanic isolation capability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

Different parts of the circuit breaker have different isolation characteristics: the solid state switch provides compact, localized isolation suitable for normal operation with small air gap, while the mechanical contact system provides robust, extended isolation for failure modes. This local differentiation allows the small air gap to be maintained overall while ensuring galvanic isolation reliability when needed.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The mechanical contact system is pre-positioned to provide galvanic isolation in case of semiconductor failure. By having the mechanical contacts ready in advance, the system ensures that when a failure occurs, robust galvanic isolation can be immediately established, compensating for the reduced isolation capability of the smaller air gap during normal operation.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11777301B2Solid state circuit interrupter with solid state interlocking mechanism

Publication Date: 2023.10.03 EATON INTELLIGENT POWER LTD

AI summary

A system includes a first circuit breaker comprising a first solid state switch, first mechanical contacts, and a current sensor structured to sense current flowing through the first circuit breaker, and a second circuit breaker electrically coupled to the first circuit breaker and being structured to interrupt current flowing to the first circuit breaker, wherein the first circuit breaker is structured to transmit, to the second circuit breaker, a request upon detecting a failure mode, and wherein the second circuit breaker is structured to interrupt current flowing to the first circuit breaker in response to receiving the request, and the first circuit breaker is further structured to open the first mechanical contacts when the current flowing through the first circuit breaker drops to a predetermined level.