Research On Fault-Tolerant Permanent-Magnet Synchronous Machines With Improved Reluctance Torque And Salient Ratio

Fault-tolerant permanent magnet(FTPM)synchronous machine inherits the advantages of high torque density,high power density and high efficiency,the fault-tolerant capacity of the permanent magnet machine is also improved.Thence,it is widely favored by transportation,aerospace,national defense and military industry and other fields.However,the existing FTPM machines mostly adopt the design of the single-layer concentrated windings,and the difference of slot-pole number of the existing FTPM machines is mostly equal to 2.Because of the concentration of the magnetic circuit,the reluctance torque and salient ratio of the existing FTPM machines are very low.Moreover,it also leads to the over-voltage of high field weakening and the difficulty of sensorless operation.According to the above reasons,this paper presents a new designed FTPM machine with enhanced reluctance torque and salient ratio.Theoretical analyses of the reluctance torque and salient ratio are carried out to find out the key factors that affect the reluctance torque and salient ratio.The influences of slot-pole combination on the fault-tolerant capacity of the machine are systematically analyzed,and the factors such as output torque performance,rotor loss and torque ripple are also considered.Based on the above analyses,the selection range of the slot-pole combination of the FTPM machine has been expanded.Then,this paper selects a new slot-pole combination to break through the traditional selection principle which difference of slot-pole number is equal to 2.Afterwards,it takes both high salient ratio and high reluctance torque as the goal,and improves the performance of the new FTPM machine by the multi-objective optimization method.The main research results of this paper include the following aspects:1.The expression of the q-and d-axis inductance of the insert permanent magnet machine considering cross magnetic coupling is deduced accurately.Besides,the principle of the salient ratio of the insert permanent magnet machine is analyzed,and the key factors which influence the salient ratio are proved.The torque analysis model considering magnetic field saturation and cross coupling is constructed.The accurate separation of the reluctance torque in the machine is deduced,which lays a theoretical foundation for the promotion of the reluctance torque of the machine.2.Introduce the coupling factor and based on the relationship between the height of the coupling factor and the fault-tolerant capacity of the machine to study the fault-tolerant capacity under different slot-pole combinations and different winding structures.It integrates all factors such as the output torque performance,rotor loss,and torque ripple to propose a feasible scheme in slot-pole combination of the five-phase FTPM machines.3.A new 20-slot/14-pole FTPM machine is designed and optimized.Due to the contradiction between the reluctance torque and the salient ratio in the single parameter optimization process,the multi-objective optimization method is introduced to optimize the two parameters comprehensively.4.Establish the finite element simulation model of the final prototype scheme.Then,analyze and verify the electromagnetic characteristics of the new designed 20-slot/14-pole FTPM machine.Compared with the traditional 20-slot/18-pole FTPM machine,it is verified that the new designed FTPM machine has the advantages of high reluctance torque and salient ratio.5.Process the prototype and build the experimental platform.Then,test the back-EMF performance,the fault-tolerant capacity and the dynamic performance of the machine under normal operation and fault-tolerant operation state to verify its electromagnetic performance.