Regulated Capacitor Charging Circuit Using a High Reactance Transformer
AIR FORCE RESEARCH LAB KIRTLAND AFB NM DIRECTED ENERGY DIRECTORATE
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A high reactance transformer circuit is used to provide for the compact, simple, economic and reliable charging of a capacitor energy store to a predetermined and regulated voltage. The circuit can be operated from a single phase, three phase, or poly phase prime power source or service. The circuit employs a high-reactance transformer in combination with a phase-programmed switch. The transformer impedance limits the surge current loading on the prime power source. The phase-programmed switch is used to achieve the voltage regulation. The transformer secondary is rectified and is wound to provide the desired charge voltage on the capacitor store. The controller commands the primary switch that begins the charging cycle by closing at a predetermined phase relation to the prime power a.c. alternating current source. The predetermined phase is necessary to control the in-rush current to the primary of the transformer. The primary switch may be a fast solid state type such as an SCR Silicon Controlled Rectifier. The same primary switch opens, or recovers in the open state at a current zero crossing, to remove the primary voltage when the capacitor store reaches full charge, and thus provides regulation of the charging voltage. The repetition rate of the charging circuit is limited to approximately 25 of the prime power a.c. source frequency for three phase applications and approximately 8 of the a.c. source frequency for single phase applications. The accuracy of the regulation also depends on the maximum repetition rate in relation to the source frequency.
- Electrical and Electronic Equipment