I have been researching cycloconverters, on and off whenever time permits, since 1975. It is an interesting area of research because there are many problems yet to be solved and also because there is very little research being done on the subject.
I have concentrated on improved phase control techniques, and the application of these techniques to low cost cycloconverter configurations, particularly 2 and 3-pulse circuits, although the techniques are applicable to any pulse number.
A full description of the research up to 1995 can be found in my PhD thesis, available in Acrobat PDF format:
Download PhD Thesis, thesis.pdf (517kB)
Download Appendix B
Download Appendix C
Download Appendix D
Download Appendix E
Download Appendix F
Since completing the thesis, new phase locked loop software for determining the mains phase has been developed. The original technique, which used voltage zero crossings to detect the mains phase, was found to fail when large commutation notches due to a weak supply were present. This was corrected by using a full analog sine-cosine correlator to detect the mains phase.
Please contact me if more information is required.
The first commercial application for the new 3-pulse cycloconverter is a 1500kVA inching drive for the synchronous motor driven mills at a Canadian copper mine. The mill motors are normally operated direct on line and are started as induction motors using their wound rotor damper windings, but a low speed variable frequency, variable voltage drive is required to turn the mills for maintenance. The new 3-pulse cycloconverter proved ideal for this application.
A description of the drive can be found in the following report, available in Acrobat PDF format:
Download mill drive report, mill.pdf (73kB)
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