Study on reducing the charge delay of the no-insulation HTS coil after solder impregnation

A new kind of Impregnation method using conductive material, solder, was proposed recently. Experimental results showed that the solder impregnation (SIM) method was a feasible method for fixing no-insulation (NI) coils. However, the charge delay of the solder impregnated coil is too long which is one of the shortcomings of this method. Therefore, this paper focuses on using the proportional and integral (PI) feedback control of the power supply to reduce the charge time of the SIM coil. Comparing the charge delay of the SIM coil without and with the PI control, the time to reach the target magnetic could be reduced from about 350 s to about 20 s and the relative overshoot could be limited within 4%. The test results show that the charge delay of the SIM coil can be well addressed. Moreover, for comparison, an insulation coil and a NI coil were both fabricated and tested.