Programmable overload circuit

Details Programmable overload circuit Programmable overload circuit

1979-07-30

1981-09-22

Salce, Patrick R.

Electricity: electrical systems and devices

Safety and protection of systems and devices

Motor protective condition responsive circuits

361 96, 361 25, 364492, 364480, 318800, 318334, H02H 7085

Patent

active

042913551

ABSTRACT:
Disclosed is an overload protective circuit for an electric motor which is adaped to monitor and track motor temperature as a function of an operating parameter, namely armature current. The motor's armature current is sensed and converted to a multi-bit digital signal which is used to address a programmable read only memory (PROM) which has been pre-programmed with discrete digital values of temperature for a plurality of armature currents for the motor being protected. The digital address signal for the armature motor current is periodically updated at a relatively rapid rate and depending upon the armature current sensed, multi-bit temperature values are outputted from the PROM to a digital latch which operates a relatively slower rate to output another address back to the PROM so as to predict what the temperature will be at the next time increment based on the present current value and the present temperature. When predetermined temperature levels are reached, two bits of the PROM's output are respectively adapted to provide an alarm signal, and then a subsequent trip signal which is adapted to deenergize the motor.

REFERENCES:
patent: 3814913 (1974-06-01), Ironside et al.
patent: 3854354 (1974-10-01), Boothman
patent: 3964020 (1976-06-01), Dickerson
patent: 4021700 (1977-05-01), Ellis-Anwyl
patent: 4071745 (1978-01-01), Hall
patent: 4115860 (1978-09-01), Atwater
patent: 4125895 (1978-11-01), Buhlmann
patent: 4161027 (1979-07-01), Russell
patent: 4174496 (1979-11-01), McFall et al.
patent: 4204249 (1980-05-01), Dye et al.
"Fault Protection with a Digital Computer", by G. D. Rockefeller, I.E.E.E. Transactions on Power Apparatus, vol. PA S-88, No. 4, Apr. 1969.

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