Fast Semiconductor Switching Modules for Transformer-Coupled LC Inversion Generators

The recent availability of fast high-power semiconductor switches makes the transformer coupled LC inversion generator (TCLCG) topology a very promising candidate for the realization of reliable, multi-kHz repetition rate pulse generators with an output voltage in the range of 200 kV and more. Usage of 1:1 transformers instead of closing switches in each generator stage reduces the total number of switches inside the TCLCG to only one, independent of the numbers of stages. Thus, problem of synchronization as in Marx-generators or classical LC inversion generators can be omitted. In principle, capacitors are initially charged to the charging voltage, whereas the odd-numbered of each stage are charged with the opposite polarity to the even-numbered capacitors. Fast voltage inversion of the even-numbered capacitors leads to efficient voltage multiplication provided the semiconductor switching module will be sufficiently fast to minimize switching losses. For initial investigations, a special asymmetrically compensated three-stage test TCLCG was designed and set up. Three high-voltage semiconductor switching modules were experimentally tested in detail; two 20-kV high-voltage switching modules consisting of a series arrangement of 15 Si-based insulated gate bipolar transistors or 15 SiC-based MOSFETs, with in each case 1700-V breakdown voltage, and a fast experimental 10-kV thyristor switching module with kilo ampere current carrying capability. The achievable output signal rise time and generator efficiency for different electrical loads (resistive, capacitive, or inductive) are discussed.