Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific quantity comparison means
Patent
1986-06-06
1988-03-15
Leung, Philip H.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific quantity comparison means
361 93, 361187, H02H 326
Patent
active
047316918
ABSTRACT:
A symmetry sensing safety circuit for automatically stopping electrical current flow through a thyristor to an electrical device which is supplied by a source of alternating current electrical energy. The symmetry sensing safety circuit includes a current sensing circuit operatively associated in series with the thyristor and the electrical device for sensing the electrical current flow; an amplifier circuit operatively associated with the current sensing circuit for generating a signal which is proportional to the amplitude and direction of the sensed electrical current flow; an integrating circuit operatively associated with the amplifier circuit for generating a signal which is proportional to the amplitude and direction of the signal generated by the amplifier circuit integrated over a predetermined time interval; a comparison circuit operatively associated with the integrating circuit for generating a signal indicating when the signal generated by the integrating circuit is outside of a predetermined range of values; a relay control circuit operatively associated with the comparison circuit for generating a triggering signal whenever the comparison circuit generates the signal indicating the signal generated by the integrating circuit is outside of the predetermined range of values; an electromechanical relay operatively associated with the relay control circuit and with the source of electrical energy for switching on and off the electrical current flow to the thyristor in response to the triggering signal.
REFERENCES:
patent: 3671761 (1972-06-01), Shibuya et al.
patent: 3886932 (1975-06-01), Suessmilch
patent: 3976918 (1976-08-01), Clark
patent: 4020394 (1977-04-01), Potash
patent: 4295177 (1981-10-01), Woodhouse et al.
patent: 4346424 (1982-08-01), Hansen
Gaffin Jeffrey A.
Jodziewicz Matthew F.
Kleinberg Marvin H.
Leung Philip H.
National Technical Systems
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