Alternator Power Conditioning for Launchers
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A high-energy pulse-discharge is needed to drive an electromagnetic (EM) or an electro-thermal-chemical (ETC) launcher. Various pulse power generators have been examined and used. Capacitor-based power supplies are convenient for laboratory launchers, but supplies based on rotating machines-alternators and homopolar generators-are generally more weight efficient and practical for storing, generating and shaping pulses for multi-shot, fieldable launchers. Alternators are the most flexible of the rotating machines, are better matched to the variable impedance of the launcher, and avoid the use of opening switches which are difficult to implement for repetitive and reliable operation. Also, a single pulse generator can be used to power several lethality and survivability platforms. Several alternator configurations are possible, each involving different pole geometries, numbers of poles and output phases. These configurations are in turn associated with a power converter system. The switch requirements can be met for small-caliber EM railguns and for ETC guns of all caliber by near-term silicon thyristors. For large caliber EM railguns, triggered vacuum switches are viable, although they may have to be augmented with diodes or other devices to ensure their recovery after each cycle. In the long term, thyristors based on silicon carbide offer the most promise for all applications because they can operate at 3 to 5 times the current density and electric field intensity of silicon devices.