Brian Wolhaupter with Advisor Prof. Kiruba S. Haran

This project aims to produce an inverter to drive superconducting electric machines. Superconducting electric machines have two main challenges from an electronics design standpoint: low temperatures and significant power requirements. The low temperatures are particularly challenging because few electronic devices can operate at the temperatures necessary to support a superconducting machine (typically between 50 and 100 Kelvin). These temperatures eliminate silicon carbide as a viable semiconductor because the on-state resistance increases significantly at these temperatures leading to unacceptably high losses in the power semiconductors. Gallium nitride field effect transistors exhibit improved performances at cryogenic temperatures, reducing the losses in the device and making them viable for the power levels required for superconducting electric machines. As a result, GaNFETs have been chosen for the cryogenic inverter project.

In the past year, a cryogenic power converter prototype was assembled and tested. It highlighted the limitations of off-the-shelf power isolators for gate drive circuits that are not ground referenced. To address the limitations, a power isolation circuit has been designed and is currently being tested at room temperature and at cryogenic temperatures. In the next year, a small-scale prototype of the final inverter will be tested to make sure all the components can operate at the intended power levels and temperatures.