Research On The Electrical Faults And Reliability Of Dual-windings Brushless DC Motor

Compared with the traditional brush DC motor, the Rare Earth PermanentMagnet Brushless DC Motor has many obvious advantages in terms of size, weight,power density, service life, and etc.. Rare Earth Permanent Magnet Brushless DCMotor has achieved an increasingly wide range of applications in recent years. Atpresent, Power actuation system is gradually replacing the traditional hydraulic andpneumatic drive and the trend has become a consensus in aerospace equipments.The motor will play an irreplaceable role in the procedure, and the Rare EarthPermanent Magnet Brushless DC Motor will suffer a greater attention because of itsunique advantages.However, given the high demands of the aerospace equipment for safety, thereliability of the motor will become more prominent. To address the electrical faultsof windings and permanent magnet and the reliability of the motor, this dissertationfocuses on the following aspects.To begin with, regarding the reliability the motor and the complexity of motorcontrol, this dissertation determined the design of the dual-windings. According tothe two windings embedding methods, three dual-windings designs that is theparallel-every slot type, the parallel-same slot type and the tandem structure typehas been studied. This dissertation studied the distribution characteristics andpole-slot assort of the parallel-every slot type and the parallel-same slot type.Moreover, to complete the interference that through the mutual inductancecoupling between dual-windings, the mutual inductance matrix of dual-windings iscounted for every slot and same slot type motor. Integer slot and fractional slotmotor, two methods that is dual-windings placed in different modules of the motorfractional slot concentrated winding are adopted to effectively reduce the mutualinductance of dual-windings. Take into account the safety of the motor when thewinding occurring short-circuit condition, the analytical method and theElectromagnetic Finite Element Method (FEM) is employed to calculate the size ofthe short-circuit current and another set of winding current when a set of windingoccurring short-circuit among turns, short-circuit between phases and short-circuitto ground.Furthermore, as for the high-temperature demagnetization and applied reversemagnetic field demagnetization of permanent magnet, the temperature rise of themotor and the armature reaction magnetic field under extreme short-circuitcondition is calculated respectively. Actually, the motor will run under theapproximate vacuum environment, in order to control the motor temperature rise, this dissertation introduces a radiation screen placed the appropriate position abovethe motor, and take contact with other equipment to radiating for the motor. Thetemperature rise situation of the isolated motor and the motor with a cooling deviceis compared to verify the effectiveness of the cooling device.Finally, to calculate quantitatively the reliability of the motor, the physical andmathematical models of three structured motor that are a single motor, the parallelstructure type, the series structure type are establishment. Through the calculation offailure rate of each of the various components, and then estimate the reliability ofthe motor. The results demonstrate that the redundancy design can significantlyimprove the reliability of motor. Further, adopt derating design for the lessreliability components to effectively improve the reliability of motor weak parts,thereby enhancing the reliability of the motor.