Analysis And Study Of New Winding Topology And Operating Characteristics Of Five-phase Induction Motors

With the advantages of low voltage and high power,good fault tolerance and low torque ripple,multiphase motors are more suitable for highly reliable AC drives in naval,electric vehicle and aerospace applications.The reliability of multiphase motors is an important indicator of their performance and requires them to have good fault tolerance in the event of a fault.Multiphase motors have a variety of stator winding topologies and changing the stator winding topology provides a solution to improve the reliability of the motor.The thesis proposes new winding topologies for five-phase induction motors,analyses and investigates different winding topologies for five-phase induction motors by means of opencircuit performance,losses,fault-tolerance performance and temperature distribution.The winding arrangement rules of multiphase motors are analysed,and guidelines for the composition of multiphase motor windings based on an arbitrary number of phases are proposed.Two new combined winding topologies are proposed: pentagon-star winding and star-pentacal winding.A comparison of the magnet motive force and operating performance of five-phase induction motors with different topologies shows that: under normal operation,the minimum number of harmonic magnet motive force generated by the fundamental current of the combined winding motor is 19;under an open-circuit fault in one phase,the pentagon winding motor and the pentagon-star winding motor are characterised by low distortion of the magnet motive force,low torque ripple,high maximum torque multiplier and low voltage unbalance coefficient.Based on the vector decoupling transformation,an equivalent circuit iron loss calculation model for a five-phase induction motor with all winding topologies is developed to address the shortcomings of the existing five-phase induction motor model which ignores the influence of iron loss.The voltage of each winding branch of the motor is calculated according to the finite element model,and the equivalent circuit iron loss model is introduced to calculate the iron loss of the five-phase induction motor under steady-state operation.The correctness and validity of the model are verified by the time-stepping finite element method and experimental tests,which prove that the proposed five-phase induction motor with pentagon-star winding has lower losses than the five-phase induction motor with pentagon winding.The given fault tolerant currents of the five-phase induction motor with different winding topologies are calculated based on the principle of constant total magnet motive force and maximum output torque.The results show that the fault-tolerant control method based on the principle of maximum output torque has a higher derating factor and ensures that the given fault-tolerant current produces a circular magnet motive force.The load carrying capacity of a five-phase induction motor with different winding topologies is calculated,and the pentagon wind ing motor has the maximum load carrying capacity,followed by the pentagon-star winding motor proposed in this thesis.The fault-tolerant control model is established according to the above control method,and the positive and negative sequence components of the 3rd harmonic plane are controlled using dual PI to calculate the current and torque of the motor under fault-tolerant control.A three-dimensional full-domain temperature field mathematical model of the motor in no-load operation,rated-load operation,open-loop operation and faulttolerant operation is developed.The maximum temperature rise of a five-phase induction motor with different winding topologies are compared with the dynamic temperature profile under a open-circuit fault,demonstrating that the star-winding motor has the lowest temperature rise under fault and the pentagon-star winding motor has a lower temperature rise compared to the pentagon winding motor.The temperatures at different locations of the motor are extracted and compared w ith the experimental results to verify the validity of the temperature field model and the accuracy of the loss calculation results in Chapter 3.The effect of different winding topologies on the temperature rise of five-phase induction motors is revealed.Based on the operating characteristics of five-phase induction motors with different winding topologies in different states,the pentagon-star winding is specified as the preferred winding for five-phase induction motors..