Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1992-09-23
1994-02-01
Pellinen, A. D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361 24, 361103, H02H 708
Patent
active
052837084
ABSTRACT:
A device protects an electric load, such as a motor, from excessive current levels. The current flows from a source to the load through a switch and a primary winding of a current sensing transformer. The voltage across a secondary winding of the current sensing transformer is rectified to produce a voltage which is measured to determine the level of current through the load. The voltage across the secondary winding also powers components of the device. In a first mode of operation, current from the secondary winding is applied to charge a power supply capacitor. In a second mode of operation the level of the rectified voltage is sensed to produce a sample of the level of the current flowing through the load. From this sample the change in temperature of the load since a previous sample is calculated and used to derive the present load temperature. When the present load temperature exceeds a defined threshold level, the switch is opened to disconnect the load from the electricity source.
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Pages 2, 10 and 11 from an Allen-Bradley catalog entitled IEC Contactors, Overload Relays & Enclosed Starters.
The Allen-Bradley Product Data Bulletin for the 100 Line of Contactors and overload relays.
Allen-Bradley Company Inc.
Jackson S.
Pellinen A. D.
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