100_A_CLASS_SMALL_AC_TRANSFORMER_USING_OXIDE_SUPERCONDUCTOR_______________________________________________________________*
 *____

                          __OPERATING_AT_LIQUID_NITROGEN_TEMPERATURE____________________________________________



            E._S._Otabe______, H. Matsuoka, M. Izawa, T. Matsushita, J. Fujikami*, K. Ohmatsu*

          Department of Computer Science and Electronics, Kyushu Institute of Technology,

                                          680-4 Kawazu, Iizuka 820-8502, Japan

                 Basic High Technology Laboratories, Sumitomo Electric Industries, Ltd.,

                               1-1-3 Shimaya, Konohana-ku, Osaka 554-0024, Japan



    A small superconducting transformer of 100 A class was designed and fabricated using a Bi-

2223 oxide superconductor as a compact AC current source of a laboratory-scale.  For the primary

winding, a copper wire of 0.2 mmOE was wound on a bobbin of 54 mm in diameter by 300 turns.

A  silver-sheathed  Bi-2223  multifilamentary  tape  with  61  filaments  was  used  for  the  secondary

winding.  Its DC critical current was 30 A at 77.3 K and 0 T and three tapes connected in parallel

were wound to attain a sufficient secondary current.  The diameter of a bobbin for the secondary

winding  was  64  mm.   An  iron  core  was  used  to  get  a  good  coupling  between  the  primary  and

secondary windings.  The observed ratio of transformer was 79.3 at 77.3 K in the frequency range

of  30-100  Hz.   The  secondary  AC  current  reached  80  A(rms)  without  a  distortion  of  the  wave

form  in  this  frequency  range.   A  similar  transformer  with  the  maximum  secondary  current  of

about 500 A is designed using a superconducting tape of the critical current of 45 A.