Princeton Power Systems (United states)

AC loss presents a major design consideration for superconducting rotating machines. Superconducting DC field coils on the rotor are exposed to high-order-harmonic ripple fields from the AC stator, which can create an excessive heat load on the cryogenic system. To mitigate these effects, an electromagnetic (EM) shield surrounding the outermost surface of the rotor is usually employed to intercept stator harmonics before they can interact with the superconducting coils and other components inside the cold environment. Due to the important role of the EM shield, it is necessary to correctly characterize its behavior. The EM shield is characterized by a self-inductance and its mutual-inductance with the stator coils. These parameters can be calculated easily using 2-D analytical formulations or 2-D finite-element analysis (FEA). However, these methods tend to underestimate the inductances compared to 3-D FEA simulations which are more accurate but also more time-consuming. In this paper, we determine correction factors necessary to bring shield parameters calculated by 2-D analytical methods closer to the values obtained by 3-D FEA simulation. The corrections are independent of motor radius, and are applicable to both small and large machines. Their use enables rapid machine optimization using 2-D methods.

Superconducting machine designs have historically focused on an isolated, cryogenic rotor and conventional (copper) stator due to unacceptable levels of AC loss in a superconducting stator. Thus, AC loss reduction in the armature windings is one of the key issues for achieving practical all-superconducting motors that could deliver an unprecedented power density and significantly reduce machine complexity. In this paper, a 100 kW, 1500 rpm, all - HTS motor operating at 65 K is designed and AC loss simulations in HTS armature windings wound with different types of (RE)BCO conductor arrangements are carried out by implementing the T-A formulation and a rotating mesh using commercial FEM software COMSOL Multiphysics. Either 4 mm-wide (RE)BCO conductors, 14/2 (14 strands, each strand is 2 mm wide) (RE)BCO Roebel cables, or striated (RE)BCO conductors with four 1 mm-wide filaments are considered in the armature windings. The simulation results show that armature windings wound with Roebel cables or striated conductors can significantly reduce the AC loss in the armature windings compared to windings wound with 4 mm-wide conductors. It is also shown that the AC loss in the armature winding wound with the 4 mm-wide (RE)BCO conductors decreases with decreasing operating temperature. The AC loss reduction can be attributed to the reduced magnetic field penetration associated with the increased $I_{\mathrm {c}}$ in the winding. Finally, a 2% AC loss reduction can be achieved in the armature winding wound with (RE)BCO conductors with asymmetric $I_{\mathrm {c}}(B$ , $\theta$ ) characteristics by simply flipping the direction of the conductors of the armature winding. The simulation results in this work have practical implications for designing all-HTS superconducting rotating machines. Such machines could be suitable for H2 powered electric vehicles like large interstate trucks, heavy machinery, or locomotives.

A unique variable speed drive topology is presented. This topology has been shown to use silicon controlled rectifier switches without commutation circuitry at a frequency of 2 kHz to produce input and output waveforms with current total harmonic distortion below 3%. Furthermore, the voltage rise on the output is 1.2 v//spl mu/s without inductive filtering, which preserves motor insulation and bearing life. The topology is low cost due to its minimal switching complexity.