Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Patent
1989-04-20
1990-12-25
Pellinen, A. D.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
318474, 324127, 336233, 335298, H01F 2724
Patent
active
049807943
ABSTRACT:
A motor controller or contactor is disclosed which utilizes a non-saturating current transformer for sensing the amount of current flowing in the electrical conductor connected to the contactor. The current sensor is made of homogeneous sintered powdered metal having evenly distributed microscopic air gaps therein which increase the reluctance of the magnetic circuit but resist the influence of stray magnetic flux. This increased reluctance prevents magnetic saturation over a wide range of input current and allows the secondary of the transducer to produce a voltage which is proportional to the derivative of the primary current, that is the current being sensed by the transducer. The aforementioned voltage is linearly proportional to the derivative of the current over a wide range of primary current values. This voltage is integrated to produce an output signal which is directly proportional to the aforementioned primary current over the wide range of current values. By measuring only the derivative of the primary current, the current transducer can be significantly smaller than an equivalent current transformer. The homogenous magnetic core of powdered metal and interposed air gaps has a Rayleigh Constant .lambda. of such value .lambda.H is significantly less than the initial permeability less than the initial permeability .mu.o of the core, thus allowing the transformer to sense current over a wide range.
REFERENCES:
patent: 4071824 (1978-01-01), Kernander et al.
patent: 4255494 (1981-03-01), Reen et al.
patent: 4456867 (1984-06-01), Mallick, Jr. et al.
patent: 4597025 (1986-06-01), Rutchik et al.
patent: 4841424 (1989-06-01), Washburn et al.
IEEE Standard Dictionary of Electrical and Electronic Terms, Third Edition (1984), pp. 220 and 956.
Nilsson, James W., Electric Circuits, Addison-Wesley Publishing Co. (1983), pp. 406-407.
Moran M. J.
Osborn David
Pellinen A. D.
Westinghouse Electric Corp.
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