New Structures Of IE4 Induction Motors

In order to develop induction motors with IE4 energy efficency standard, the thesis theoretically analyzes the loss mechanisms of induction motors. It establishes the time-stepping finite element method loss model which can consider the multiple non-linear factors and the complex structural factors. Then it studies the impact of different factors on the loss and proposes ioss reducing measures. The main works are as follow.1. The calculation method of induction motors copper loss and iron loss is systematically analyzed. Aiming at iron loss method, the two-type model of iron loss, the three-type constant coefficient model of iron loss and the three-type variable coefficient model of iron loss are analyzed. Different from previous motor design using empirical coefficients roughly computing iron loss, the loss computation model based on time-stepping finite element method is established, congsidering the impact of various factors on the loss.2. In order to take advantage of the multi-slice field-circuit coupled time-stepping finite element method to accurately calculate losses of skew induction motors, study the influences of time step, slice number and mesh density on the loss computation. Then the optimal spatial-time discrete strategy is proposed, it provides important references of accurately calculating the loss factors of motors and improve the accuracy of loss calculation.3. The influence of structural factors, which are stator slot size, skewed rotors, splits, closed rotors and height are systematieally studied. It lays the oretical foundation for further research on premium efficiency motors.4. Taking a 5.5kW motor as an example, with time-stepping finite element method, it establishes optimization models of stator slot, rotor slot, stator core and rotor core, then it proposes the new structure design of induction motors.