Investigation of the Transient Inductance for a Pulsed Alternator With Fully Passive Compensation

The passively compensated pulsed alternator (PCPA) is one of the most competitive pulsed power technologies for future electromagnetic launcher systems. The PCPA is mostly designed for the high pulse repetition frequency military applications, such as the railgun, coilgun, and electrothermal chemical gun. The PCPA is a high-energy and high-power (sub-GW) electrical synchronous generator operating in a fast-transient, short-pulse regime. Due to its low internal impedance during the discharge, the pulsed alternator is capable of extremely high output current, almost two orders of magnitude higher than similar rotating synchronous generators of the same size. This paper has investigated the transient inductance of the armature winding of a PCPA, including the internal inductance and the end leakage inductance. A novel method is proposed to decrease the end leakage inductance in which the end windings are surrounded by totally enclosed conductive shields settled at the stator ends. The analytic formulas of the internal inductance and the end leakage inductance are deduced using the magnetic vector potential method. The concept of end winding shielding can be generalized to other types of compensated pulsed alternators, such as the selective PCPAs and actively compensated pulsed alternators.