Abstract: This paper discusses the propagation process of pulse waves in cables and the influence of cable length on overvoltage and pulse rise time at the coil ends. Due to the increase in coil voltage and extremely uneven voltage distribution, partial discharge occurs in the coil, leading to insulation breakdown when insulation aging is severe. To effectively extract partial discharge signals, a high-frequency pulse current sensor was designed, and a bridge-like circuit was constructed specifically for partial discharge testing of SPWM variable frequency motor coils. Test results show that this partial discharge testing system can detect partial discharge signals under strong interference (SPWM). Keywords: Sinusoidal pulse width modulation (SPWM) Partial discharge coil insulation current sensor [b][align=center]Measurement of Partial Discharge of Winding in SPWM Inverter-Fed Induction Motors Yu Qinxue1 Ren Wene1 A. Cavallini2 GC Montanari2 M.Tassinri2 (1. Xi'an Jiaotong University Xi'an 710049 China 2. Bologna University Bologna 40136 Italy）[/align][/b] Abstract: The propagation process of wave pulse in the cable and influence of cable length onovervoltage and wavefront time of winding are discussed in this paper. The partial discharge (PD) ofmotor winding can produce due to voltagein creasing and distorted distribution of electric field. PD willcause insulation aging, and even leads to breakdown of motor winding. Therefore it is necessary to set up PD detecting system for SPWM motor. In this paper, the current transducer (CT) of high frequency has been developed and circuit similar to bridge for measuring A partial discharge (PD) device has been designed. Experimental results show that it is possible to detect and record PD in a high-disturbance environment. Keywords: Sine pulse width modulation (SPWM), partial discharge (PD), winding insulation, current transducer (CT) 1 Introduction In recent years, with the rapid development of science and technology, the application of variable frequency speed control motors has become increasingly common. However, the phenomenon of premature insulation failure in a large number of variable frequency speed control motors has been constantly emerging both domestically and internationally. Some variable frequency motors have a lifespan of only 1 to 2 years, and some even experience insulation breakdown during trial operation. Moreover, the breakdown usually occurs in the inter-turn insulation, which has attracted special attention from relevant scholars and experts at home and abroad. It is also a new challenge brought to electrical insulation technology by the application of power inverter technology. Premature insulation failure in variable frequency speed control motors is caused by heat, space charge, and partial discharge [1, 2], with partial discharge being one of the main causes. Due to impedance mismatch between the motor and the cable, refraction and reflection occur. The reflected and refracted waves cause oscillating overvoltages on the motor terminals, which are sometimes twice the voltage of 50Hz. Furthermore, the rise time of the SPWM waveform is extremely short, typically 50ns to 0.1μs. The pulse voltage distribution in the motor coil is highly uneven, with approximately 75% of the overvoltage amplitude occurring on the first few turns of the motor winding. This means the inter-turn voltage on the first turn exceeds the average inter-turn voltage by more than 10 times. Combined with approximately twice the overshoot voltage at the motor terminals, this will cause partial discharge between the turns within the motor, leading to deterioration of insulation performance and a shortened lifespan. Therefore, the measurement and study of the partial discharge mechanism in variable frequency speed control motors have significant theoretical and practical value. [align=center][b]For more details, please click: Measurement of Partial Discharge in SPWM Variable Frequency Speed ​​Control Motor Coils[/b][/align]