Browse Prior Art Database

DC AC Converter

IP.com Disclosure Number: IPCOM000089908D
Original Publication Date: 1968-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Prange, R: AUTHOR

Abstract

This circuit arrangement provides a switch which turns off a converter with inductive input impedance, at zero current. In drawing 1, SCR1, SCR2, L, C, D1, D2 and transformer Tr comprise a DC-AC converter. DC power is applied to the circuit between terminals A and B. Gating signals are alternatively applied to SCR1 and SCR2 gates respectively.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

DC AC Converter

This circuit arrangement provides a switch which turns off a converter with inductive input impedance, at zero current. In drawing 1, SCR1, SCR2, L, C, D1, D2 and transformer Tr comprise a DC-AC converter. DC power is applied to the circuit between terminals A and B. Gating signals are alternatively applied to SCR1 and SCR2 gates respectively.

Input impedance of this parallel type DC-AC converter is essentially inductive. Therefore a problem of switching off the power supply occurs.

Electromechanical switches are often used for this purpose. This is a lack of reliability due to induced voltages. This switch includes diode D3 and controlled rectifier SCR3, which enables switching power off at zero current, by automatically delaying this switching up to a zero current moment.

During switching time from one SCR1 or SCR2 to the other, this converter feeds a negative current back to the power supply. As shown in drawing 2, after each half converter cycle, a negative current flows into the input circuit which then crosses zero level. The current characteristic is used for switching off purposes. Switching on is obtained by applying and maintaining a DC level on SCR3 gate. Switching off is realized by removing this DC voltage level at any time. The effect is delayed by the circuit itself until the input current itself crosses zero, maximum equals T/2.

1

Page 2 of 2

2

[This page contains 3 pictures or other non-text objects]