Capabilities, performance, and future possibilities of high frequency polyprase resonant converters

High frequency polyphase resonant power conditioning (PRPC) techniques developed at Los Alamos National Laboratory (LANL) are now being utilized for the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS) accelerator klystron RF amplifier power systems. Three different styles of polyphase resonant converter modulators were developed for the SNS application. The various systems operate up to 140 kV, or 11 MW pulses, or up to 1.1 MW average power, all from a DC input of plusmn1.2 kV. Component improvements realized with the SNS effort coupled with new applied engineering techniques have resulted in dramatic changes in RF power conditioning topology. As an example, the high-voltage transformers are less than 1% the size and weight of equivalent 60 Hz versions. With resonant conversion techniques, load protective networks are not required. A shorted load detunes the resonance and little power transfer can occur. This provides for power conditioning systems that are inherently self-protective, with automatic fault "ride-through" capabilities. By altering the Los Alamos design, higher power and CW power conditioning systems can be realized without further demands of the individual component voltage or current capabilities. This has led to designs that can accommodate 30 MW long pulse applications and megawatt class CW systems with high efficiencies. The same PRPC techniques can also be utilized for lower average power systems (~250 kW). This permits the use of significantly higher frequency conversion techniques that result in extremely compact systems with shorter pulse (10 to 100 us) capabilities. These lower power PRPC systems may be suitable for medical Linacs and mobile RF systems. This paper will briefly review the performance achieved for the SNS accelerator and examine designs for high efficiency megawatt class CW systems and 30 MW peak power applications. The devices and designs for compact higher frequency converters utilized for shorter pulse, lower average power applications will also be presented