【作者】 俞清；

【导师】 白保东；

【作者基本信息】 沈阳工业大学 ， 电机与电器， 2010， 硕士

【摘要】 变压器直流偏磁现象对变压器的正常运行会产生不利的影响,诸如励磁电流畸变、高次谐波成分及其相应损耗的增加、铁心高度饱和引起的漏磁通的增加,以及由此引发的局部过热、绝缘损害、系统电压下降等一系列问题。目前对变压器中直流偏磁现象的机理研究和定量分析尚处于初步阶段,在变压器的设计过程中也没有完全考虑直流偏磁效应。隔爆电机的实际运行也是一个较为复杂的物理过程,工作时不可避免地要产生损耗,这些损耗最终绝大部分变成热量,引起电机各部分温度的升高,从而关系到电机的运行寿命和可靠性。随着电磁场理论知识的不断完善、传热学知识的不断成熟以及计算机技术的不断发展,采用方便快捷的方法准确的计算这些电磁装置的电磁场和温度场也势在必行。本文首先根据变压器直流偏磁的原理,利用双爱波斯坦方圈装置对在不同工作点、不同偏置水平条件下的铁心磁滞回线进行了深入的实验研究,测量了铁磁材料在实际偏磁时的交直流共同作用时的磁滞回线和损耗曲线。考虑铁磁材料的饱和特性,分别运用电路的方法和场路耦合法对变压器直流偏磁情况下的励磁电流进行了仿真计算,将两种仿真结果进行比较,得出了场路耦合模型的结果更具有工程实际意义。并以磁场计算结果为基础,通过编程计算变压器的空载损耗。利用场路耦合法对隔爆电机的电磁分布情况、电磁转矩和电流进行了仿真,以电压源为载荷,计算了三相隔爆异步电动机的运行性能,并且所得结果与设计结果相符,进一步验证了此方法的正确性,同时也得出了场路耦合法的普遍性和实用性。最后将传热学知识和有限元法与电机的实际性能结合起来,确定了电机内导热体的等效导热系数和各散热面的表面散热系数,用有限元分析软件对三相隔爆异步电动机进行了温度场分析,全面了解了电机内部各点的温度分布情况。这对于全面认识电机内部的温升情况,检验设计的电机的温升性能具有一定的指导意义。更多还原

【Abstract】 The DC bias magnetization phenomena is harmful to the characteristics of the transformers on line. It causes the distortion of magnetizing current and the increasing of harmonics leakage magnetic flux and corresponding losses, which in turn result in a series of problems such as the local overheating, insulation damage and system voltage drop. However, the mechanism analysis and the analysis in quantities are still in initial stage as well as the effect of DC bias magnetization has not fully considered in the process of the transformer design. The actual operation of the flameproof motor is also a very complex physical process. The losses are produced inevitably by the motor on operation. The majority of these losses will cause overheating eventually which will increase the temperature. The temperature rise in flameproof induction motor may be harmful for the insulation which directly determines the operation life of the motor and the reliability. With the improvement of electromagnetic theory, the mature of heat transfer knowledge and the development of computer technology, using the fast and convenient method to calculate the electromagnetic and temperature fields accurately in these electromagnetic devices is also imperatively.Based on the principle of DC bias magnetization, this paper uses the pairs of Epstein square coil equipment to further study the core hysteresis loop under the conditions of different operating point and different levels of bias. The hysteresis loop and iron loss curve of the ferromagnetic material under DC bias and AC combined action in actual DC bias are obtained. Taking the saturation characteristics of ferromagnetic materials into account, this paper use the circuit method and the field-circuit coupled method to simulate and calculate the magnetizing current of transformer in the conditions of the DC bias magnetization respectively. The field-circuit coupled model is more practical significance in engineering by comparing the two kinds of simulation results. Then, the loss curve is input to the transformer circuit-field coupled model. Based on the magnetic field calculations, the core loss is calculated and analyzed by programming. Then, the electromagnetic distribution, electromagnetic torque and current of three-phase flameproof induction motor are simulated by using the field-circuit coupled method. As a result, the operation performance of the flameproof motor is calculated. The results are consistent with the design. It is further to validate the correctness of field-circuit coupled method as well as the universality and practicality.This paper combines the knowledge of heat transfer and the finite element method with the actual performance of the motor. The equivalent coefficient of heat conductivity and the coefficient of heat convection in the motor are determined. The 3-D temperature of the flameproof induction motor is calculated by using the finite element method. It can be accurately understanding of the transient temperature distribution of the motor through the calculation of the temperature field in this motor. It is a powerful analytical tool in guiding the design of motor.更多还原