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Frequency Converter

IP.com Disclosure Number: IPCOM000074598D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Peard, M: AUTHOR

Abstract

Shown is a high-efficiency frequency converter that permits the frequency of a sine wave to be divided by an integer N. This division is completed by thyristors which are fired in such a way that the output wave is composed of N positive half-cycles followed by N negative half-cycles of the input wave. It comprises two intermediate tapped transformers, four thyristors, a logic circuit for providing the firing pulses to the thyristor gates and a filter Which rejects the unwanted harmonics of the output wave.

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Frequency Converter

Shown is a high-efficiency frequency converter that permits the frequency of a sine wave to be divided by an integer N. This division is completed by thyristors which are fired in such a way that the output wave is composed of N positive half-cycles followed by N negative half-cycles of the input wave. It comprises two intermediate tapped transformers, four thyristors, a logic circuit for providing the firing pulses to the thyristor gates and a filter Which rejects the unwanted harmonics of the output wave.

For clarity, assume that N is equal to 3. During the first half-cycle THA is fired and due to the arrangement of transformers, Vout is equal to A Vin/2 (A being a constant). During the second half-cycle THC is fired and Vout is equal to -A Vin. During the third half-cycle THA is fired and Vout is equal to A Vin/2. During the fourth and sixth half-cycles THB is fired and Vout is equal to A Vin/2 and during the fifth half-cycle THD is fired and Vout is equal to -A Vin.

A logic, not shown, provides firing pulses to thyristors at suitable times, and a filter, not shown, rejects the fifth harmonic of the output wave.

To avoid short circuits, a three-winding supply transformer feeds a three- winding output transformer through THA, THB which are connected respectively, during alternations 1 and 3 and 4 and 6 to two different windings. Thus, whatever the voltage-current phase lag may be, no short circuit can occur between opposite voltage points, s...