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Accurate AC Sensor Using a Secondary Winding of a 50/60 Hz Transformer

IP.com Disclosure Number: IPCOM000100323D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Egan, PK: AUTHOR [+2]

Abstract

This is a method of sensing AC waveforms accurately on a secondary output of a 50/60 Hz transformer that eliminates the distortion of the waveform due to output loading. This distortion is caused by the IR losses in the 50/60 Hz transformer.

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Accurate AC Sensor Using a Secondary Winding of a 50/60 Hz Transformer

       This is a method of sensing AC waveforms accurately on a
secondary output of a 50/60 Hz transformer that eliminates the
distortion of the waveform due to output loading.  This distortion is
caused by the IR losses in the 50/60 Hz transformer.

      Shown in the figure is a block diagram of this AC sense
circuit.  Because the distortion of the waveform V1 is caused by IR
losses, the original waveform can be reproduced by adding a voltage
proportional to the output current to the distorted waveform.

      The two inputs to this circuit are the distorted AC waveform V1
and the output winding current I1.  This circuit will weigh each AC
input appropriately and add them together to create an undistorted
waveform that accurately resembles the original primary waveform.

      The peak of this waveform will be used to determine the AC line
voltage.  I1 is sensed by R1 and amplified by M1 to create a voltage
waveform V2 proportional to the output current I1.

      The weighted sum of waveform V2 and the rectified waveform V1
is processed by a peak-detector M2.  The output of M2 is used to
accurately determine the AC input voltage.