For service professionals working with large electric motors and generators, machines with voltage ratings 5 kV and higher can be vulnerable to invisible threats of partial discharge (PD). Corona and PD activity have long been a challenge to detect before failure occurs. Traditionally, detecting these issues required indirect methods like radio interference voltage (RIV) testing, ultrasonic detection or offline insulation tests. But recent advances in partial discharge imaging—sometimes called corona cameras—are giving engineers and technicians a powerful new tool: the ability to see electrical discharge activity directly and in real time. 

Para los profesionales que trabajan con grandes motores y generadores eléctricos, las máquinas con tensiones nominales de 5 kV o superiores pueden ser vulnerables a amenazas invisibles de descargas parciales (DP). Detectar la actividad corona y las DP antes de que se produzca un fallo ha sido un desafío durante mucho tiempo. Tradicionalmente, detectar estos problemas requería métodos indirectos como pruebas de voltaje de radio interferencia (RIV), detección ultrasónica o pruebas de aislamiento a máquina parada. Sin embargo, los recientes avances en imágenes de descargas parciales, a veces llamadas cámaras corona, brindan a ingenieros y técnicos una nueva y poderosa herramienta: la capacidad de ver la actividad de descargas eléctricas directamente y en tiempo real.

This webinar recording reviews the failures associated with 3-phase motors on Variable Frequency Drives (VFDs) and how to rewind to limit future failures.

This paper describes partial discharge, explains how to detect it, and offers repair solutions.

Concerns about partial discharge (PD) used to be limited to repairers and users of machines rated over 7 kV. PD is a common consideration for machines rated 11 kV and higher. This article will describe PD, explain how to detect it, and offer repair solutions. Discussion includes:

• What is partial discharge?
• Air as an insulator
• Can we fix it?
• Detecting partial discharge
• Monitoring partial discharge activity
• Partial discharge in random windings

When rewinding a motor, the service center is restricted by the original design. Sometimes, we encounter a motor design we wish had never been developed. The random-wound, 2300-volt motor design falls into that category. The great challenge to the service center is in successfully rewinding this design while maintaining profit.