  This paper describes electrical design and operational characteristics of a
zero-voltage-switching 20 kHz polyphase bridge, boost converter/modulator for
klystron pulse application. The DC-DC converter derives the buss voltages from
a standard 13.8 kV to 2300 Y substation cast-core transformer. Energy storage
and filtering is provided by self-clearing metallized hazy polypropylene
traction capacitors. Three "H-Bridge" IGBT switching networks are used to
generate the polyphase 20 kHz transformers primary drive waveforms. The 20 kHz
drive waveforms are chirped the appropriate duration to generate the desired
klystron pulse width. PWM (pulse width modulation) of the individual 20 kHz
pulses is utilized to provide regulated output waveforms with adaptive
feedforward and feedback techniques. The boost transformer design utilizes
amorphous nanocrystalline material that provides the required low core loss at
design flux levels and switching frequencies. Resonant shunt peaking is used on
the transformer secondary to boost output voltage and resonate transformer
leakage inductance. With the appropriate transformer leakage inductance and
peaking capacitance, zero-voltage-switching of the IGBT's is attained,
minimizing switching losses. A review of these design parameters and a
comparison of computer calculations, scale model, and first article results
will be performed.
