Turn-to-turn loss and mechanical behaviors of no-insulation layer-wound coil with active feedback control

The no-insulationhigh-temperaturesuperconductinglayer-woundcoil has a long chargingdelay, whichcan be mitigatedthroughproportionaland integral(PI) activefeedbackcontrols.However, PI controlrequiresa larger powersupplycurrent,potentiallycausingadditionalenergyloss and mechanicaldamage.Thus,analyzingthe electromagneticandmechanicalbehaviorsof the layer-woundcoil with PI controlis necessary. In this article,a hybridnumerical,combiningthe equivalentcircuitnetworkmodelwith the finiteelementmodel,is usedto calculatethe turn-to-turnloss andmechanicalresponseof the coil with PI control.The numericalcalculationdemonstratesthat the layer-woundcoil with PIcontrolrequiresa largerpowersupplyand generateshigherturn-to-turnloss energy and hoop stresscomparedwith a coilwithoutPI control.Higherstressis generatedin the coil with PI control,whilethe differencein the hoopstressisrelativelysmallerthan that in the turn-to-turnloss. In a backgroundfield of 10 T, the differencein the hoopstressis20 MPa.The loss of energyincreasesrapidlywith increasingnumberof turnsin the axialdirection.Thus,a coil withfeweraxial turns is preferredto reducethe turn-to-turnloss and hoop stress.In addition,increasingthe chargingtime candecreasethe loss of energy and peak stres