Feasibility Study of High Current Transistor D.C. Choppers

  • B. Y. M. Marogy

    Student thesis: Master's Thesis


    This dissertation describes an investigation into the feasibility of high current transistor d.c. choppers.

    Present d.c. choppers employ thyristors and are expensive due to the turn-off circuits required. The use of low cost power transistors in electric vehicle chopper controllers is investigated, and a brief survey of power transistors has been carried out to establish which transistors are most economical
    for use in choppers.

    A transistor d.c. chopper employing Germanium transistors and capable of controlling 400 A at 72 V was designed and constructed: special design consideration was given to suppression of voltage transients and minimisation of power losses in the chopper during switching. Results of laboratory tests have shown the transistor chopper to be reliable and highly efficient. The replacement of the Germanium output transistors, used in the initial design, by Silicon power transistors resulted in the elimination of current sharing problems and a negligible effect on chopper efficiency.

    The experimental chopper was costed and found to be cheap relative to a comparable thyristor chopper, thus offering the possibility of rapid industrial acceptance.
    Date of AwardJan 1975
    Original languageEnglish


    • Transistors

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