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AC Voltage Present Sensor

IP.com Disclosure Number: IPCOM000088924D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Braithwaite, KA: AUTHOR

Abstract

The AC voltage present sensor is capable of detecting both single and three phase AC voltage for a wide frequency band over a wide range of input voltages.

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AC Voltage Present Sensor

The AC voltage present sensor is capable of detecting both single and three phase AC voltage for a wide frequency band over a wide range of input voltages.

The references are established by the Zener diodes 12 in the Y input lines, and the voltages to be sensed are applied to the X input lines. In normal operation, the input voltage will be above the reference voltage, thus causing the optical isolator diode 10 to conduct. Since the input voltage is a varying AC voltage, the diode 10 will conduct for a part of each cycle.

This turns on the optical isolation transistor 14 for the time the associated diode conducts. The result is a pulse output from the transistor 14 for normal operation and a steady state high output for a fault condition. These signals, from the appropriate phase input, are applied to the (-) terminal of the respective comparator amplifier 16, which is utilized to give sharp on and off switching and, also, to invert the input signals. Thus, normal operation still produces a pulse output from the comparator. However, the down pulses are now up pulses, etc. This can best be seen when it is realized that the input of the comparator amplifier 16 as marked, that is, when the input voltage at the minus terminal is below the input voltage at the plus terminal, a high output results. Similarly, when the voltage at the minus terminal passes to a more positive condition than the voltage at the positive terminal, a down output is o...