High-voltage switch gear protection circuit

Details High-voltage switch gear protection circuit High-voltage switch gear protection circuit

1999-03-19

2001-03-13

Sherry, Michael J. (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific current responsive fault sensor

C361S005000, C361S008000

Reexamination Certificate

active

06201678

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention generally relates to a switching circuit and more particularly to a circuit used as a switch gear circuit in electric vehicles for controlling capacitive loads.
Electric vehicles typically include switch gear circuits designed to control power supply and usage of capacitive loads. In most arrangements a precharge circuit pathway is provided for charging a capacitive load by selectively coupling it with a power source. After the capacitive load is charged sufficiently, a main circuit pathway, which is in parallel with the precharge pathway, connects the power source to the load. After a preselected amount of time, the precharge circuit pathway is opened while the main pathway remains closed.
In typical situations it becomes necessary to disconnect the capacitive load from the power source. Therefore, a relay that can consistently break large currents at high voltages has been included in the main pathway. While such an arrangement has. proven usable, those skilled in the art are always striving to make improvements. One improvement that could be made is to use less-expensive components, which would make the overall system more economical.
This invention provides a circuit arrangement that eliminates the need for a relatively expensive high-voltage relay switch in the main circuit pathway. This invention replaces the relatively expensive component with a very low cost arrangement that is reliable and economical.
SUMMARY OF THE INVENTION
In general terms, this invention is a switch gear circuit for use in electrical vehicles. The circuit is useful for selectively connecting a power source with a capacitive load and especially for making failsafe disconnections. A first circuit pathway includes a first switch element that is selectively closed to allow current to flow between the power source and the load. The first switch element is selectively opened only when the voltage across the switch element is less than a predetermined threshold value. A second pathway in parallel with the first includes a second switch element in series with a circuit breaker element. The second switch element is selectively closed to allow current to flow through the second pathway so that the voltage across the first switched element becomes less than the predetermined threshold value, which allows the first switch element to be selectively opened. The second switch element, which is protected from potentially damaging high currents by the circuit breaker element, is later opened to completely disconnect the power source from the load.
Providing a parallel second pathway allows for a high-current, low-voltage relay switch or contactor to be used in the main pathway, which presents a substantial savings compared to conventional high-voltage relay switches that would otherwise be required.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the presently preferred embodiment. The drawings that accompany the detailed description can be described as follows.


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patent: 5805393 (1998-09-01), Thomas

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