The Variable Parameters Iron Loss Model For Considering Harmonics

Due to the complex factors such as saturation, harmonic fields and magnetization style, the prediction of iron losses in induction motors is still difficult in engineering practice. This thesis build tree iron loss model, i.e. tree-term iron loss model with variable parameters, two-term iron loss model with variable parameters, and fine analyzed the loss of the induction motor with the method of the theoretical analysis, finite element calculation and experimental study, the main works are as below.1. This thesis proposed a three-term precise iron losses prediction model with piecewise variable coefficients based on Bertotti’s three-term iron loss model, in which an additional flux density term and an additional flux density term are introduced to consider the increased eddy current loss and local hysteresis loss caused by magnetic saturation and harmonic field, respectively. Meanwhile, the main loss coefficients are varying with the amplitude and frequency of flux density, by which the influence of the fundamental and harmonic field on iron losses are considered effectively, at the same time, the hysteresis loss, eddy current loss and excess loss can also be predicted accurately. To verify the effectiveness of the model, the experimental validation are carried out. It reveals that the iron loss predicted by the presented model agree well with the tested ones.2. This thesis proposes a two-term piecewise variable parameter model for precise prediction of iron losses in induction motors. In this model, two additional flux density terms are used to reflect the non-linear characteristics of the magnetic materials, and the main loss parameters of the this model are piecewise varying with frequency and flux density. Meanwhile, the fine analysis of iron losses caused by fundamental and harmonic fields can also be carried out with the proposed model. Experimental validation are also carried out on the above motors.3. Due to the coaction of supply harmonics and harmonic fields inside the motors, the mechanism and distribution characteristics of iron losses become more complicated when an induction motor is supplied with inverter. This thesis firstly analyzes the variation of flux density in the typical positions of stator and rotor core for a 5.5 kW inverter-fed induction motor. By using the two-term piecewise variable parameter model, the iron loss of inverter-fed induction motor is studied, the distribution regularity of hysteresis loss and eddy current loss in stator and rotor core is revealed, and the characteristics of additional iron loss caused by harmonic fields are also acquired.