Research On Design Methods And Key Technologies Of Air-core Compensated Pulsed Alternator

Compensated Pulsed Alternator(CPA), serving as a kinetic energy high-power pulsed source, is a rotating electrical machine to supply giant pulse current to load by means of electromagnetic induction and magnetic flux compensation. Compared with the pulsed power sources with other types of energy storage, the air-core cpa made of fiber reinforced epoxy composite with high strength-to-density ratio has the comprehensive advantage of energy density and power density. The air-core CPA is widely used as the pulsed power supply of new concept weapons like electromagnetic gun, electromagnetic chemical gun and directed energy weapons.The preliminary study of air-core CPA mainly lies in the engineering prototype and the study of operation principle and design theory is not well-developed. Some key technologies are not mastered. In recent years, the research of key technology and basic theory is paid more and more attentions for the development of more compact and lighter next generation pulsed power source. This article is specified in the aspects of electromagnetic and structural design, analysis methods and corresponding key technologies. A novel topology is presented and the theoretical and experimental research is done for exploring the rule of design of air-core CPA.This article explored the operation principle in the aspects of electromagnetic theory for clarifying the analysis and design. The compensation principle and the armature reaction flux distribution characteristic are analyzed in the aspect of electromagnetic theory.The transient inductance of armature winding has a great impact on CPA performance. The formula for calculating the transient inductance of the armature winding is presented with account for the non-uniform distribution of the pulse current flowing in the armature conductors (skin effect and proximity effect) and the compensation effect in the shield.There are no magnetic circuits in air-core CPA which are confined by ferromagnetic materials. It is very difficult to calculate the electromagnetic parameters correctly by traditional magnetic circuit method. Therefore, A three-dimensional finite element simulation model of electromagnetic field is established for calculating the electromagnetic parameters. The no-load and discharge electromagnetic field and the eddy current field in the compensation shield were simulated. The self-excitation process was simulated and the self-excitation current was calculated. The influence factors on air-core CPA performance were presented.During discharge, the electromagnetic force mainly acted on the armature winding and compensation shield in air-core CPA. Therefore, it is necessary to make the strength assessment to guide its mechanical design. The distribution characteristics of electromagnetic force in the whole air-core CPA were presented before and during discharge. Due to the special structure and the orthotropic characteristic of fiber reinforced epoxy composite in air-core CPA, the safe thickness of the epoxy resin between the compensation shield and carbon fiber reinforced epoxy band is decided by strain analysis. The method of choosing the optimum ratio of epoxy resin and fiber is concluded by calculating the stress formula in air-core rotor. A hybrid multi-rim air-core rotor with comprehensive advantages is presented.To solve the inconsistency between the self-excitation efficiency and output performance of air-core CPA, a novel topology–Dual Stator-Winding Passive CPA (DSW-PCPA) is presented in this paper. The unique feature of the topology is that there are two armature windings in the stator, the primary armature winding for providing the main output pulse, and the secondary armature winding for providing the voltage for self-excitation. The two armature windings are located in the stator, but not the rotor. The advantage of this configuration is that only one middle energy level brush and slip ring mechanism is needed for self-excitation, by which the long life and high reliability are obtained. This approach allows the optimization of each armature winding to its specific duty cycle to solve the constrained relationship between the self-excitation efficiency and magnitude of pulse current.Finally, A DSW-PCPA engineering prototype was fabricated. The special machining techniques were presented, including the shape of slotless windings and the integration of subassembly of stator and rotor components. The results of experiment validate the results of simulation and pay foundation for the design, fabrication and experiment of CPA engineering prototype.