DC arc detection and prevention circuit and method

Details DC arc detection and prevention circuit and method DC arc detection and prevention circuit and method

2002-02-11

2004-01-27

Riley, Shawn (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

Ground fault protection

C361S097000

Reexamination Certificate

active

06683766

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the art of electrical arc detection and prevention, and, more specifically, to a system and method for detecting and preventing imminent DC arcs based upon a pre-arc condition.
BACKGROUND OF THE INVENTION
Electrical arcs comprise a significant source of potential fires and component damage in many different environments that employ electrical power. Electrical arcs generally occur when an electrical connector is disconnected thereby creating an air gap between the two sides of the electrical connector. At the beginning of the disconnection, the separation distance between the two sides of the connector is very small. As a result, the voltage across the air gap produces a very large electrical field in terms of volts per millimeter. This large electrical field causes the ignition of an electrical arc between the two sides of the connector.
Various methods are known to detect electrical arcs in Alternating Current (AC) systems. However, it is much more difficult to prevent an electrical arc in a Direct Current (DC) system because DC currents do not have zero-crossing moments, which are used to detect arcs in AC systems.
DC systems are employed in a variety of environments, including, for example, electrical systems of automotive vehicles. Traditionally, electrical systems in automotive vehicles have been based on a 12-volt power supply. It has been determined by the inventors that DC arcs generally do not persist unless the voltage across the air gap is at least 14 volts. Thus, arcs in traditional 12-volt automotive electrical systems have traditionally been relatively uncommon and/or less severe. However, a current developmental trend in automotive vehicles is to incorporate electrical systems having power supplies larger than the traditional 12 volts. A relatively common modern automotive electrical system includes a 42-volt power supply, and some vehicles, such as electric vehicles, may incorporate even higher voltage power supplies. The inventors hereof have recognized that these modem automotive electrical systems pose a much greater risk of igniting an electrical arc when an air gap is created by a connector being disconnected. Further, because DC arcs ignite at current levels lower than normal load currents and at voltage levels below the power supply output, common over-current or over-voltage protection devices (such as fuses, breakers, etc.) will not function to detect or prevent an arc. Thus, the inventors have recognized that there is a need for a new system for detecting and preventing electrical arcs in DC systems.
SUMMARY OF THE INVENTION
The present invention is directed to a system and method of detecting the imminent ignition of a DC arc prior to the actual arc ignition itself. The present invention detects an “arc precursor condition” that is indicative of an imminent arc ignition.
The inventors have recognized that the DC current and DC voltage across an electrical connector during a disconnection are not, as has been commonly believed in the industry, mere noise signals. Rather, the DC current and DC voltage signals across an air gap follow a particular pattern during a disconnection and prior to the ignition of an electrical arc across the two sides of the connector. According to one specific aspect of the invention, either the DC current or DC voltage across the air gap comprise the arc precursor condition that is used to detect an imminent arc ignition. According to a further specific aspect of the present invention, a sudden drop in the DC current across the connector is detected and considered indicative of an imminent arc ignition.
Other aspects and advantages of the present invention will become apparent to those skilled in the art in light of the detailed description and claims of this application.


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