Research On Wide Flux Weakening Speed Range Of Permanent Magnet Synchronous Spindle Motor

With high efficiency, low torque ripple, high dynamic performance,high energy density and so on,permanent magnet synchronous motor(PMSM) has been widely studied and applied.It is difficult to increase the motor speed by flux weakening,because permeability of permanent magnets is approximately equal to air.The flux weakening for PMSM is accomplished by applying a large demagnetizing current in the d-axis of the permanent magnets,which will increase the winding copper loss,reduce converter efficiency and demagnetize the permanent magnets irreversibly. This paper focused on enhancing the capability of flux weakening for PMSM,so we will research on the following aspects.Firstly,we establish equivalent vector circuit of PMSM based on principle of flux weakening,and derive the essential cause of difficulty in flux weakening for PMSM. We proposed a new motor with shunt-tooth in stator, derive the capability of flux weakening and output torque from its equivalent vector circuit,and study design principle of the new motor.Secondly, we build the finite element model of the new motor with the help of FLUX,compare the new design with its counterpart by FEA,and summary the influence of shunt-tooth on performance of the motor,which will offer direction for optimal design of the new motor.In addition,In order to validate the previous circuit analysis,we will accurately calculate motor parameters such as magnet flux linkage,d-axis and q-axis inductance.Thirdly,we will research on the influence of high flux weakening capability on performance of the new motor.we derive the relationship between the new motor power factor and its flux weakening capability,and provide effective method to improve the new motor power factor at low speed.we also study torque ripple of the new motor in flux weakening region,and search optimal measure to reduce its torque ripple.Finally, Based on previous analysis,a prototype motor is manufactured and experimented.Compared to FEA,the test result verify flux weakening capacity of the new design concept.