基于介质损耗分析研究变频电机绝缘老化特性

变频牵引调速电机匝间绝缘承受来自逆变器的连续高压脉冲方波的作用,其老化机理与工频正弦电压作用下具有很大差异。笔者通过采用两种电压源对模拟变频电机匝间绝缘和对地绝缘的绞线对试样进行老化试验,测量了tanδ随老化时间的变化趋势,分析了电压形式对匝间绝缘和对地绝缘介质损耗产生和发展的作用机理。试验结果表明:脉冲电压下,匝间绝缘内部有放电发生时,放电与空间电荷协同作用使绝缘缺陷迅速增多;无放电时空间电荷反复注入和抽出造成绝缘损伤。交流电压下绝缘介质发热主要由局部放电造成,而脉冲电压下主要是由空间电荷所导致。对地绝缘由于其绝缘结构,呈现槽放电现象,空间电荷的引入大大加速了绝缘的老化。

Study on Aging Characteristics of Insulation in Inverter-fed Traction Motor Based on Dielectric Loss

Stator insulation of inverter-fed motor experiences continuous impulses with significant harmonic and transient. The insulation aging mechanisms are quite different under the effects of continuous impulse and under sine wave. Contrast aging tests are carried out on twisted pairs simulating inter-turn insulation and insulation to ground of inverter-fed traction motor under AC and square wave pulse conditions. The variations of tan δ concerning different aging factors with aging time and measuring voltage are investigated. The mechanism of a form of voltage and the turn-to-turn insulation to insulation dielectric loss and development are analyzed. The experimental results show that when measuring voltage is pulse voltage and the discharge occurring within the interturn insulation, partial discharge (PD) and space charge result in sharp increase of insulation defects. When no discharge into space charge repeatedly and extract insulation caused insulation injury. PD results in insulation heat under AC voltage, and space charge results in insulation heat under square wave pulse condition. Slot discharge occurs due to the special insulation structure of insulation to ground. Space charge is likely to be the key factor resulting in aging of insulation materials under continuous impulse.