Passive Clamping Circuit for Fast Capacitor Discharge in DC Breakers

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Solution Overview

Problem

Existing circuit breakers for aircraft DC networks face challenges in efficiently dissipating inductively stored energy during fault conditions, leading to high voltage peaks that can damage components due to slow discharge times of primary capacitors, necessitating unnecessary throttling of the main switching unit.

Innovation Solution

Incorporating a discharge circuit with secondary capacitors and decoupling resistors to quickly discharge primary capacitors when the main switching unit is closed, reducing discharge time from seconds to microseconds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a clamping circuit with primary capacitors is used to absorb energy during fault conditions, then overvoltage protection is improved, but the discharge time becomes too slow (seconds), causing voltage peaks that can damage components

Engineering Contradiction:

Improveovervoltage protectionVSAvoiddischarge time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The clamping circuit is segmented into two distinct capacitor groups: primary capacitors for energy absorption during faults, and secondary capacitors for rapid discharge. This segmentation allows each capacitor type to be optimized for its specific function, resolving the contradiction between protection capability and discharge speed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The secondary capacitors act as an intermediary energy storage element that bridges the primary capacitors and the rest of the circuit. They quickly accept energy from the primary capacitors during discharge, enabling rapid voltage equalization and preventing damaging voltage peaks.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the main switching unit is throttled to prevent voltage peaks, then component protection is improved, but system performance and power transmission capability deteriorate

Engineering Contradiction:

Improvevoltage peak damageVSAvoidsystem performance

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The secondary capacitors are pre-configured and ready to immediately accept energy from the primary capacitors when a fault occurs. This preliminary arrangement of discharge paths allows rapid energy dissipation without requiring throttling of the main switching unit, thus maintaining system performance while preventing voltage peak damage.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If primary capacitors are used for energy absorption, then clamping capability is improved, but leakage current increases due to slow discharge

Engineering Contradiction:

Improveclamping capabilityVSAvoidleakage current

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The discharge circuit enables periodic energy transfer from primary to secondary capacitors. The secondary capacitors rapidly discharge the stored energy in controlled periods, preventing continuous leakage current while maintaining clamping capability. This periodic action converts continuous energy loss into controlled, intermittent discharge events.

Inventive Principle:

Principle #19Periodic action

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

The solution enables rapid discharge of capacitors, preventing voltage spikes and reducing leakage current, thus enhancing system performance and reliability without significant complexity or additional losses.

Implementation Method 1

at least one primary capacitor configured to be charged during clamping when the main switching unit is opened

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the discharge circuit includes at least one secondary capacitor and is configured to discharge the at least one primary capacitor when the main switching unit is closed

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

a passive transient suppression component... configured to be charged during clamping

Methodology Applied

Scientific EffectTransient suppression: Joule Heating

Data Source

PatentEP4645359A1Circuit breaker with a passive clamping circuit including capacitors, operation method, DC network and aircraft

Publication Date: 2025.11.05 AIRBUS (SAS)

Figure 1
Figure 2~3

AI summary

The invention relates to a circuit breaker (14) comprising a main switching unit (16) configured to be switched off in the event of a fault, and a clamping circuit (18) for absorbing energy and protecting against overvoltage wherein the clamping circuit (18) is connected in parallel to the main switching unit (16) and comprises a primary passive protective circuit (26) including a passive transient suppression component (20.2, 20.2, 20.3). In order to provide an enhance protection against overvoltage, especially for use on aircraft, it is proposed that the clamping circuit (18) comprises at least one primary capacitor (C1, C2) configured to be charged during clamping when the main switching unit (16) is opened, wherein the clamping circuit (18) further comprises a discharge circuit (28) including at least one secondary capacitor (C3, C4, C5) and configured to discharge the at least one primary capacitor (C1, C2) when the main switching unit (16) is closed.