Stress Analysis And Structure Optimization Of The Compulsator

The compensated pulsed alternator(CPA)is a special motor which provides pulsed power to electromagnetic railguns,at work the energy is first stored in the rotor in the form of kinetic energy and is quickly output to the load during discharge.The CPA usually works at high speed to obtain higher rotor energy,so the rotor is subjected to a large centrifugal force,in addition,CPA uses the principles of magnetic flux compression to reduce the internal inductance of the motor during discharge,making the amplitude of the discharge current extremely high,and the motor is greatly impacted by the electromagnetic force,which has a great influence on the structural strength of the motor.More importantly,composite materials are used to make motor parts in the new generation of CPAs,and the stress analysis of composites is more complex than conventional materials.To ensure the safety of the CPA and make full use of the strength of the structure,the stress characters on CPA has been studied in this paper.Most components of the CPA are made of composite materials with high strength density ratio.In order to analyze the stress of the components in the alternator,we need to understand the characteristics and analysis methods of the composite material itself in the first place.Before the analysis,a three-dimensional finite element analysis model of CPA is established,the in fluence of processing method and raw material content on the mechanical properties of com posite components in CPA is analyzed.The stress distribution of the composite rotor under the action of centrifugal force is calculated by the theoretical method,and the prestress distribution in the rotor is studied according to the stress optimization method which can be used in the processing of the composite parts.It is found that the method of filament winding cannot effectively counteract the radial centrifugal force of the rotor,and the circumferential stress of the rotor is comparatively low,which indicates that the high strength of the composite material has not been fully utilized,and it can be further optimized.For the effect of electromagnetic force on CPA,the electromagnetic force produced by CPA discharge is calculated first,and the effect of electromagnetic force on the stator rotor is analyzed according to the characteristics of the stator rotor.For the stator,it is determined that the effect of electromagnetic force belongs to the dynamic problems,then the general law of impact load is analyzed,and the conclusion that the maximum reaction produced by load is only related to the inherent cycle of the structure is obtained.The intrinsic period corresponding to the CPA stator is found by a trial calculation model,and then the influence of different materials and different parts on the whole inherent period of the CPA stator is studied,the suitable material and structure are selected to avoid the vibration in the stator of the motor caused by the electromagnetic forces.For the rotor,because the rotor has no restraint in the direction of rotation,the effect of the electroma gnetic force on the rotor can be classified as a static problems,and t he effect of the electromagnetic force on the CPA rotor is calculated.As for the effect of centrifugal force on the rotor,the structural strength of rotor at rated speed is checked first,although the strength of the rotor meets the requirements,the design and assembly methods of the components need to be improved.Then the corresponding stress analysis and structure optimization are carried out for the rotor yoke,the rotor bandage,the carbon fiber support and the rotating shaft.The maximum allowable speed of the rotor can be raised to 42000 rpm,and the stress distribution at this speed is calculated.