Study Of Novel High Efficiency Single-phase Induction Motor With Three Series-connected Windings

Simple structure,low cost,reliable operating performance and convenient maintains are the main reasons for favoring the use of single-phase motors,which are supplied with single-phase source.In remote and rural regions where only a single-phase power supply is available,the single-phase induction motors are widely used for the daily life and power drive.It is not economic to use single-phase induction motor when the rated power of the motor exceeds 0.5kW.As the increasing demand of the energy,the manufacture and application of high efficiency motors are important for the conservation of energy.Therefore,the development of the single-phase induction motor with high efficiency is of great significance.Comparing with normal single-phase induction motors,three-phase induction motors have higher efficiency and larger scale power.Both of the connecting the appropriate phase converters and changing the wiring mode of the motor stator windings are effective ways for three-phase electrical motors supplied by the single-phase power.And using capacitor as the phase converter is the simplest and practical method.Using capacitor as the phase converter,many wiring methods have already been put forward.Being restricted by the structure,some motors with the existed wiring methods only operating with the single-phase supply have lower efficiency and some motors have complex start-up circuits,which disagree with promotion.This paper put forward a novel high efficiency single-phase induction motor with three stator windings.Based on the symmetrical component method and the transient mathematical model,the comprehensive,in-depth study on the design and calculating method of the novel high efficiency single-phase induction motor with three series-connected windings has been done,and transient and steady-state performance of the proposed motor is explained in the paper.The main contents are as follows:A novel high efficiency motor is designed in this paper.Different from normal single-phase induction motors,the proposed motor has three-phase symmetrical stator windings.The three windings in the stator are connected in series,and the capacitors used as phase converters are connected to the windings in parallel.Operating under the rated load,the proposed motor has almost the same efficiency and volume of the three-phase induction motor.Furthermore,it has a higher power factor.In comparison with the ordinary single-phase induction motor,it has the advantages of higher efficiency and smaller volume,thus can take place of the ordinary single-phase induction motor.Under the condition of the smallest unbalance voltage,the relationship between the motor structural parameters and the capacitors is deduced by using symmetrical component method and the method of synthesizing current.Based on the symmetrical component method and equivalent circuit of three-phase induction motors,the formula for calculating the capacitors is ensured.The capacitors are optimized by selecting the smallest negative-sequence current coefficient or the highest efficiency under rated load as the objective functions.For the symmetry is importance to the performance of the proposed motor,the ideal capacitors are determined by using the hybrid golden section method.The performance calculation method of the proposed motor is deduced.The electromagnetic torque is calculated by the currents in rotor.The zero-sequence current is considered in calculation of the stator copper loss.The formula can be used in the performance calculation of the single-phase motor with three symmetrical windings.Because of the imbalance current density in the stator windings,the wire diameter and slot size are redesigned.Using the steady state performance formulas and FEA method,the performance of the motor redesigned is analyzed,which proves that the different wire diameter and slot size of three windings have little influence on the motor performance.The pattern of three-phase induction motors can be used as the novel high efficiency motor.A 4-pole 2.2 kW prototype is designed with the dimension of Y2100L1-4 three-phase induction motors.The performances tests are performed on the proposed motor.The experimental results agree with the calculated ones well.Based on the stator winding endpoint equation,the constraint condition of the stator winding terminal voltage is derived,the uniform state equation in a stationary coordinate system is established,furthermore,the ABC model of the stator and the d-q model of the rotor are used.For actual application,the starting operation and stable operation process is simulated and comparatively analyzed.A one start-up capacitor circuit of the proposed motor is put forward and proved reliably by the experiments.To making a further research on the novel high efficiency single-phase motor,the symmetrical operation conditions of the single-phase induction motors with SEMIHEX^TM and Y connection method are deduced and the formula for calculating the phase-convert capacitor is derived by using symmetrical component method.With the instantaneous symmetrical component model of the novel high efficiency single-phase induction motor,the single-phase motors with SEMIHEX^TM and Y connection is simulated.The performance tests of motors with Y connection, SEMIHEX^TM connection method and the novel three-winding in series connection method are performed and compared with each other.The novel single-phase induction motor has the advantages of higher efficiency,higher max output power and better symmetry,thus can take place of the ordinary single-phase induction motor.Construction,performance steady and transient state process of the novel high efficiency single-phase motor has been further researched in this thesis,and some academic value and the project practical value conclusion is obtained in this thesis.