High-Tc superconducting power supplies are devices which can deliver kA+ currents into superconducting circuits without introducing any heat pathways from the ambient laboratory environment. Experimental results from a prototype optically switched, high-Tc superconducting half-wave transformer rectifier submerged in liquid nitrogen are presented. The entire secondary side of the rectifier is comprised of commercially manufactured coated conductors. This includes the transformer secondary, the bridge, and an HTS double pancake load coil. The switch is opened by applying nanosecond bursts of infrared light which transition the bridge into a resistive state. The frequency of the transformer primary is 1 Hz and the bridge is switched using optical radiation from a benchtop Nd:YAG laser with a wavelength of 1.064 μm. The pulse repetition rate is 35 kHz with pulse duration’s of 200 nanoseconds. Using this configuration, 100 A is injected into 220 μH load coil in approximately 60 seconds. The voltage measured over the bridge exceeds 100 mV and lasts approximately 3 ms each cycle or a duty cycle of 0.3%. The measured resistance is several milliohms, significantly higher than is measured using other switching mechanisms such as dynamic resistance or Jc(B,θ). Increasing the primary frequency dramatically increases the charging speed of the device.
This work was supported by a faculty research establishment grant from Victoria University of Wellington and in part by the New Zealand Ministry of Business, Innovation and Employment under the Advanced Energy Technology Platform program “High power electric motors for large scale transport” contract number RTVU2004
Keywords: High-Tc Superconductors, Optical Switching, Power Electronics, Transformer Rectifier