Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1983-09-14
1985-11-12
Pellinen, A. D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361 31, H02H 3087
Patent
active
045531870
ABSTRACT:
An overload detection circuit protects a motor against currents above rated current that persist for certain exposure times. The allowable exposure times are inversely related to the degree of overload current. The circuit has two overload current sensors with two respective overload thresholds. These are both connected to a pulse generating circuit and the pulse rate is accelerated when the second overload threshold is reached. The pulse generating circuit couples pulses to a pair of cascaded counters which generate a fault signal when a predetermined count is reached. The pulse generating circuit includes an integrator with a capacitor that must be discharged, before another pulse can be generated. The pulse generating circuit includes a comparator which operates a switch to discharge the capacitor shortly before coupling each pulse to the counters, to prevent a delay that would otherwise occur between signals from the integrator circuit.
REFERENCES:
patent: 3419757 (1968-12-01), Steen
patent: 3831061 (1974-08-01), Boyd
patent: 3959704 (1976-05-01), McCrea
patent: 4021700 (1977-05-01), Ellis-Anwyl
patent: 4327391 (1980-01-01), Grzebielski
Reliance Electric Company, Instruction Manual for Max Pak Plus Spindle Drive, Sep. 1981, pp. 29-32.
Burns James A.
Nolan Dennis C.
Allen-Bradley Company
Choe Hong K.
Pellinen A. D.
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