With consideration of both the operating properties from cryogenic MOSFETs and refrigerating costs from cryogenic refrigerators, this paper attempts to carry out the experimental tests and performance evaluations of state-of-the-art 650-V class MOSFETs, and thus to explore a possible design guideline for cryogenic power conversions at liquid nitrogen temperature. Three cryogenic operating behaviors of on-state resistances and breakdown voltages of five types of commercial power MOSFETs and on-state voltage across their built-in reverse diodes are tested from 300 K to 77 K. The measured on-state resistances obtained in low-current tests show almost double-exponential functional relations with the operating temperatures, while the other two cryogenic parameters are directly or inversely proportional to the operating temperatures. Moreover, cryogenic on-state resistance behaviors in high-current tests from 20 A to 90 A are also found to have double-exponential functional relations with the operating currents. Based on the experimental results and their fitted temperature-dependent and current-dependent functions, integrated evaluation of overall energy efficiency involved with refrigerating cost is presented to form a feasible design guideline for cryogenic power conversions. Finally, two 40-kW and 4-MW boost choppers are conceptually designed and discussed to verify the proposed design guideline for the use in various MOSFET-based cryogenic power conversions.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.