Low cost circuit controller

Details Low cost circuit controller Low cost circuit controller

1994-06-01

1997-04-01

Gaffin, Jeffrey A.

Electricity: electrical systems and devices

Safety and protection of systems and devices

Motor protective condition responsive circuits

361 24, 361106, 338 22R, H02H 504

Patent

active

056172818

ABSTRACT:
A circuit controller for selectively connecting a power source to a load includes a switching mechanism, which selectively connects the power source to the load and switches a current which flows through the switching mechanism, and a substantially radiant energy dissipating positive temperature coefficient current limiter for limiting the current which flows through the switching mechanism. The switching mechanism includes a current sensor, which senses the current flowing through the switching mechanism and provides a sensed current value, and a switching controller for disconnecting the power source from the load whenever the sensed current value is above a predetermined current value. The switching mechanism may include a contactor having separable contacts which are responsive to the switching controller. The current limiter may have a first resistance which results from a first series current, and a higher second resistance which results from a second series current. The ratio of the second resistance to the first resistance may exceed 16. The current limiter may be a tungsten or, alternatively, a carbon conductor. The tungsten conductor dissipates greater than 70 percent of the energy of the short circuit current by radiation. The current limiter may further include a tubular glass cylinder which encloses the conductor therein. The cylinder may have two copper ends, each of which are electrically connected to a corresponding end of the conductor within the cylinder. The cylinder may further enclose a non-oxidizing gas, such as nitrogen, helium, argon, krypton or a halogen gas mixture. The conductor may be wound on a ceramic cylinder within the cylinder.

REFERENCES:
patent: 4315237 (1982-02-01), Middleman et al.
patent: 4549161 (1985-10-01), McTavish et al.
patent: 4893102 (1990-01-01), Bauer
patent: 5296996 (1994-03-01), Hansson et al.
Klockner-Moeller Main Catalogue (HPL 90/91 GB, FLs/Br), pp. 9/1-9/28, published May 1990 in the Federal Republic of Germany.

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