KAMAL NATH JHA
Engineers in Bethel Park, PA

5905619, May 18, 1999

Oct 15, 1997

8/951026

Kamal N. Jha - Bethel Park PA

The United States of America as represented by the United States
Department of Energy - Washington DC

H02H3/00

361 93

An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard.

5793586, Aug 11, 1998

Oct 25, 1996

8/736752

Joseph H. Rockot - N. Huntingdon PA
Harvey E. Mikesell - McMurray PA
Kamal N. Jha - Bethel Park PA

The United States of America as represented by the United States
Department of Energy - Washington DC

H02H 300

361 8

A device and a method for interrupting very high direct currents (greater than 100,000 amperes) and simultaneously blocking high voltages (greater than 600 volts). The device utilizes a mechanical switch to carry very high currents continuously with low loss and a silicon controlled rectifier (SCR) to bypass the current around the mechanical switch while its contacts are separating. A commutation circuit, connected in parallel with the SCR, turns off the SCR by utilizing a resonant circuit to divert the SCR current after the switch opens.