Browse Prior Art Database

Overcurrent Sensing

IP.com Disclosure Number: IPCOM000096959D
Original Publication Date: 1962-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Dumas, AM: AUTHOR

Abstract

The device utilizes current transformer action to monitor the current in a D.C. circuit without interrupting that current.

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Overcurrent Sensing

The device utilizes current transformer action to monitor the current in a D.C. circuit without interrupting that current.

Magnetic core 10 is biased toward a first state by winding N1. Core 10 is energized by half-wave A. C. supplied through current limiting resistor R1 and diode CR1 from terminals 12, 14. Winding N2, carrying the current to be monitored, provides MMF in the opposite direction.

The output circuit consists of diode CR2 and load resistor R2 across winding N1. Diode CR2 is poled to pass current induced by change of the flux in core 10 from its first state in response to the MMF of winding N2. The input of an alarm trigger device, such as a flip-flop, can be connected between a reference terminal 16 and output terminal 18. In an overcurrent condition, current induced in N1 is sufficient to develop a signal across R2 for triggering the flip flop.

If the core 10 is of square hysteresis loop material, the half-wave A.C. operates to drive the core into saturation. The current through winding N2 exerts a demagnetizing effect between the half wave pulses. However, the exact shape of the hysteresis loop is not critical. This is because the action is primarily that of a current transformer, with load current induced in N1 so as to oppose decrease of the flux from its half wave A. C. excited state.

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