Current imbalance can be estimated by the solution of the circuit equation, which depends on the result of the measurement of the self- and mutual inductances. Strand circuit is coupled with each other strongly, and therefore the matrix calculation is stiff. This situation leads to enhance the error of the measurement. In order to study this problem, we made a magnet, in which the cable was composed of the nine insulated strands, and measured the inductance matrix of the strand circuits by the LCR-meter. The inductance of the magnet is 11 mH, and the error of the measurement is the order of micro Henry to 10 mu H. The average coupling factor of the magnet is 0.9956, and therefore this inductance matrix is almost singular. Finally, we calculated the currents of the strand. The accuracy of the inductance measurement is the order of 5-6 digits. We used~(TM) Mathematica to solve the circuit equation, and we tested the accuracy of the calculation precision. Random number method is introduced to estimate the required accuracy of the inductance measurement. The required accuracy of the inductance measurement is the order of micro Henry in this magnet to obtain the accuracy of 5 percent for the strand currents.
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