MANUFACTURE OF HOLLOW LITZ WIRE

PURPOSE:To reduce a loss in the winding of a transformer and a chock coil in the high-frequency range, and to make the outer diameter in a small size, by forming a clearance at the center of a parent stranded wire as well as forming a fan form in a child stranded wire. CONSTITUTION:The stranding pitch in the first process is set by the rotation frequency in the direction ZaO of a bobbin 11a and the winding speed of the ra, and the stranding pitch in the second process of a child stranded wire 5 is set by the rotation in the direction ZbO of a bobbin 12b, the winding speed of the rb, and a die. The pitch in the stranding back of a grandchild stranded wire 4 is set by the rotation in the direction Zb1 of the bobbin 11b, and furthermore, the stranding pitch of the third process is set by the rotation in the direction ro of a bobbin 13c and the die. The pitch when the grandchild stranded wire 4 and the child stranded wire 5 are stranded back is set by the rotation frequency in the direction r1 of a bobbin 12c and the rc winding speed. By setting to strand back the grandchild stranded wire 20 to 50% than the pitch of the first process in the second process, and to strand the child stranded wire 40 to 60% than the pitch of the second process in the third process, a good hollow litz wire 6 is manufactured.