Effect Of Structures And Materials On The Electromagnetic Field And Temperature Field Of High-speed Permanent Magnet Generator

High-speed permanent magnet (PM) machine, because of its simple structure, large power density, material saving, high efficiency driving system, is usually used as micro-gas turbine power generation equipment, becomes one of the hot in electrotechnical field. When the high-speed PM machine rotating, the frequency of magnetic field in stator will be too high that cause high losses and temperature rise. So how to optimize high-speed PM machines by exploring new materials and structure to reduce temperature is very important. To solve these problems, the following contents are studied in this thesis:First of all, a 2-D mathematical model of transient electromagnetic field is established, transient electromagnetic field is calculated by using time stepping finite element method. The difference between electromagnetic properties of stators with semi-closed slots and closed slots is studied. Distinction of the electrical output characteristics between round windings and conventional winding is discussed, and the relationship between windings and output performance is analyzed. When parallel magnetization is introduced in rotor, air-gap flux density and the harmonic content are compared when PM is distributed and centralized, voltage and current waveforms are simulated as well.Secondly, the usefulness of several composite shield structures is discussed from the view of finding new structure and material by comparing the electrical performance and temperature distribution. Distributions of rotor eddy current loss are calculated when shield is composed by copper screen and alloy jacket or copper screen and carbon fiber bandage, and the way how the thickness of copper screen affect the rotor eddy current are studied. Carbon fiber composite materials, ceramic coating are introduced in shields, the relationship between conductivity of carbon fiber composite materials and rotor eddy loss is studied. The effect of different shield structure this thesis involved in solving temperature rising problem is discussed.Finally, the relationship of electromagnetic field, output voltage and current according to speed are obtained. Steady-state temperature field of high speed PM generator without cooling method is calculated, and 3-D steady state temperature distributions of generators under different speeds are calculated. At the same time, related test works are carried out, and the reliability of the calculation results is verified. A new cooling measure that pushes cooling air through shaft is proposed, and the relationship between wind speed and the cooling effect is analyzed, effect of cooling ability when shaft air and ceramic thermal barrier coating are both used is also studied.The conclusions received in this thesis could provide reference when high-speed permanent magnet synchronous machine is designed and optimized.