AC Solid State Power Controller Asymmetric Fault Detection

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Solution Overview

Problem

Aircraft electrical systems face damage and hazardous conditions due to asymmetric fault conditions caused by half-wave rectified AC power, which existing solid state power controllers (SSPCs) fail to detect and protect against.

Innovation Solution

An SSPC with a logic section and power section, including a microcontroller, gate drive, and signal conditioning module, detects half-wave rectified voltage and selectively turns ON or OFF to clear faults by setting status indications for 'SSPC Failed Shorted' or 'SSPC Failed Open' conditions, using body diodes and current sense resistors to manage switches and prevent damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an SSPC is used to distribute AC electrical power, then status capability and reliability are improved, but asymmetric fault detection capability deteriorates

Engineering Contradiction:

ImproveSSPC reliabilityVSAvoidasymmetric fault detection

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies preliminary action by detecting the presence of body diode conduction currents before they can cause harmful half-wave rectified output. The control circuit proactively identifies asymmetric faults by monitoring these currents and takes preventive action by controlling the switching elements to block faulty conduction paths, thereby preventing damage to downstream circuitry while maintaining the reliability benefits of SSPC technology.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If the SSPC blocks asymmetric faults, then load protection is improved, but circuit complexity increases

Engineering Contradiction:

Improveload protection from half-wave rectified powerVSAvoidSSPC circuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies self-service by utilizing the inherently present body diodes within the MOSFET switching elements for fault detection purposes. Rather than adding separate detection components, the system leverages the natural parasitic elements already present in the circuit architecture. The control circuit monitors conduction currents through these body diodes and autonomously determines asymmetric fault conditions, enabling load protection without significantly increasing external component count or circuit complexity.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS7656633B2Asymmetric fault detection and protection with AC solid state power controllers

Publication Date: 2010.02.02 HAMILTON SUNDSTRAND CORP

AI summary

An apparatus and method for protecting an AC load from half-wave rectified power detects a half-wave rectified voltage or current, sets a status indication indicating the type of asymmetric fault causing the half-wave rectified power, and selectively turns the SSPC ON or OFF depending on the type of fault. There are two example circumstances that can cause an asymmetric fault: when the SSPC is OFF and a switch is shorted (“SSPC Failed Shorted”), or when the SSPC is commanded ON and a switch remains open (“SSPC Failed Open”). If the SSPC is OFF when the half-wave rectified AC voltage or current is detected, an “SSPC Failed Shorted” status indication is set, and the SSPC is turned ON to clear the fault. If the SSPC is commanded ON when the half-wave rectified AC voltage or current is detected, an “SSPC Failed Open” status indication is set, and the SSPC is turned OFF to clear the fault.