对比测量了不同运行年限的变频牵引电机的定子绕组绝缘诊断参数，包括绝缘电阻、介质损耗因数、局部放电起始电压(PDIV)、剩余击穿电压等特征参数，以及沿绕组不同部位的绝缘材料取样进行了热失重分析(TGA)来研究绝缘老化特征。介电性能测量结果表明，与新电机相比，运行后定子绕组的绝缘介电性能有不同程度的下降，出槽口附近绝缘的老化程度高于槽内。TGA分析结果表明，使用了长达10年的牵引电机定子绕组绝缘性能略有下降，且线圈下层边的绝缘老化比上层边明显。

The characteristic parameters of the stator winding insulations in the inverter-fed traction motors with various service years, including the insulation resistance, dissipation factor, partial discharge inception voltage (PDIV) and residual breakdown voltage, are measured sequentially to analyze the insulation deterioration. The insulation materials from different sites of the insulation along the windings are sampled and analyzed with thermogravimetric analysis (TGA). The measured dielectric results show that the characteristic parameters from the stator windings decrease slightly in comparison with those of new motors. The aging degree of the insulation near the outlet slot is higher than that in the slot. Besides, the TGA results from the sampled insulation materials indicate that the stator winding insulation in the inverter-fed traction motor with a service period up to ten years shows slight deterioration. Generally, more serious deterioration in the insulation tends to appear at the bottom side of the motor coils.