Hybrid solid state/mechanical switch with failure protection
AssigneeWestinghouse Electric Corp.
InventorsDerek A. Paice, Kenneth E. Mattern
Life of this patent
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Abstract
A hybrid solid state/mechanical switch is provided with a pair of mechanical contacts connected in parallel with a solid state switching device. These components are operated by a control circuit to achieve arcless current interruption under normal conditions. A circuit breaking device, which can be operated by a crowbar circuit, provides failure protection for the hybrid switch if excessive leakage current is detected in the solid state switching device or current continues to flow through the switch at a preselected time following the occurrence of a turn-off command signal.
Claims8
A hybrid electrical switch comprising:
- a pair of terminals for connection to a power line;
- a branch circuit connected between said power line terminals, said branch circuit including the series connection of a circuit breaking device and a pair of mechanical contacts;
- a solid state switching device electrically connected in parallel with said pair of mechanical contacts;
- a crowbar circuit connected between a reference terminal and a connection point in said branch circuit located between said circuit breaking device and said pair of mechanical contacts;
- means for controlling the operation of said pair of mechanical contacts and said solid state switching device such that said solid state switching device is turned on before the closure of said mechanical contacts and is turned off after said mechanical contacts open;
- means for triggering said crowbar circuit when the leakage current through said solid state switching device exceeds a preselected magnitude;
- and
- means for triggering said crowbar circuit when current flows through said circuit breaking device for a period which exceeds a predetermined duration following the expected opening time of said pair of mechanical contacts.
A hybrid electrical switch comprising:
- a pair of terminals connected to a power line;
- a pair of mechanical contacts connected between said power line terminals;
- a branch circuit electrically connected in parallel with said pair of mechanical contacts, said branch circuit including the series connection of a circuit breaking device and a solid state switching device;
- a crowbar circuit connected between a reference terminal and a connection point in said branch circuit located between said circuit breaking device and said solid state switching device;
- means for controlling the operation of said pair o mechanical contacts and said solid state switching device such that said solid state switching device is turned on before the closure of said mechanical contacts and is turned off after said mechanical contacts open;
- means for triggering said crowbar circuit when the leakage current through said solid state switching device exceeds a preselected magnitude;
- and
- means for triggering said crowbar circuit when current flows through said circuit breaking device for a period which exceeds a predetermined duration following the expected opening time of said pair of mechanical contacts.
Dependencies are inferred from the claim text.