Calculation of the critical current in pancake-coiled long length Bi-2223/Ag tapes in non-uniform local magnetic fields perpendicular to the grain alignment axis

The DC magnetic held pattern of three pancake windings consisting of 150, 1 80 and 850 m of Bi-2223/Ag tape, was mapped within each winding volume. The analysis revealed a very non-uniform held distribution across the pancake width within each turn of the pancake. The effect of this non-uniform field across the tape width on the critical current of the pancake coil and on s hort sections within a single turn was measured. A model is proposed to exp lain the observed experimental data along with a method for correctly calcu lating the field free critical current (C) 1999 Elsevier Science Ltd. All r ights reserved.