Field Initiation Design Fundamentals for Pulsed Alternators

Efficient high-performance pulsed alternator (PA) systems have low-impedance field windings that rely on very fast current rise times in order to maintain attractive system efficiencies. These systems rely on positive feedback self-excitation, or "boot-strapping" action, to energize the field winding. The self-excitation process is typically started by a small capacitor-based power supply which is discharged (or seeded) directly into the field winding. The design of this power supply, often called the field initiation module (FIM) is critically important to the process of self-excitation. Augmented by numerical simulations, this paper examines the important aspects to consider when designing a proper FIM, including: impact on system efficiency; minimum rotor speed for proper FIM function; control schemes for triggering the FIM; and proper operating voltage for the FIM