AC Loss Calculation and Analysis in Armature Windings for Superconducting Electrical Machines

AC losses in armature windings arise from time- varying currents and fields, raising effective resistance and lowering efficiency. We compare three-phase armature winding losses for Litz wire and REBCO high-temperature superconductor (HTS) tapes, and examine how turn count and operating temperature affect them. For Litz windings, we use a hybrid analytical model that captures skin and proximity effects. For HTS windings, we develop a time-domain model that includes the angle and field-dependent critical current density J$_c$(B,θ) and power-law exponent n(B,θ). Both models are validated against finite-element method simulations. We then generate torque–speed loss maps under constraints from the drive and the cryocooler. The results provide a clear comparison of Litz and HTS armature windings across the entire operating speed range and offer recommendations for efficiency-oriented machine design and control.