Electromechanical batteries for low earth orbitsatellites

Abstract

In this thesis, a surface-mounted permanent magnet synchronous machine and flywheel are designed and optimized analytically. The machine and flywheel are supposed to be used in low earth orbit satellite as electromechanical battery. Due to the application, there is a limited amount of space for the system which set constraints on the design. The low earth orbit satellites usually include nano and micro satellites which rotate around the earth is a period of 90 minutes. the most critical part of these satellites are their batteries which supply power to a load of about 100 w during 30 minutes eclipse period . The electromechanical battery is a motor generator mode device with flywheel which is used to store kinetic energy during motor mode through the flywheel during sunlight and supply electrical power from the stored kinetic energy by the generator mode at eclipse period. Among several types of machine, the permanent magnet synchronous machine is chosen to be used in this battery with outer rotor to be suitable for the flywheel system for space applications. An analytical design method for surface mounted permanent magnet machine is described. Special attention is given to the mechanical properties of the machine to withstand high speed which has maximum of a 60000 rpm. A selection of material for the each component of the machine is considered. The development of flywheel to be a hollow cylindrical body which is composed of two parts to minimize the weight of the system and to optimize its volume and guarantee the storage and supply of enough kinetic energy.