Repeated thermal expansions and contractions their effect on long armature coil insulations

THERE has been considerable discussion among engineers interested in the operation of large turbo-generators as to the possible effects of expansion and contraction on armature coil insulation. During the past ten years, generators have increased in core length from less than 100 in. to 160 in. and generators approaching 200 in. in core length are being discussed. With increasing length of cores, it has become more important to settle this question and the tests described in this paper were undertaken three years ago with this object in view. Preliminary tests were started on May 5, 1921, in order to work out some of the details of the procedure. The investigations herein described were actually started on June 2, 1922, the test coils having been prepared just previous to that time.