METHOD OF DEMAGNETIZING CORE OF ELECTROMAGNETIC INDUCTION APPARATUS AND ELECTROMAGNETIC INDUCTION APPARATUS HAVING DEMAGNETIZING UNIT

摘要

PROBLEM TO BE SOLVED: To avoid giving electrically adverse effect on an electromagnetic induction apparatus and suppress the exciting rush current by facilitating reducing the residual flux at a lower voltage than rated voltage of this apparatus. SOLUTION: A demagnetizing a-c voltage lower than the rated voltage of a single phase transformer 10 at a frequency less than the rated frequency of the transformer is applied to a prm. low voltage winding wound round its core 10a and at least either the demagnetizing voltage or frequency is changed to reduce the residual flux in the core 10a. If the demagnetizing frequency is 1/1000 of the rated one, e.g. 0.05HZ, demagnetizing can be done by gradually reducing the applied demagnetizing voltage of 1/1000.