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. 

The 2024 NEMA MG 00001 standard introduces key updates, including new Design BE and CE motors with defined locked-rotor current limits, Class N insulation for high-temperature use, and revised stall time requirements. It adds Super Premium efficiency levels aligned with IEC IE4, adopts IEC voltage/frequency variation guidelines, and expands duty ratings for variable load/speed motors.

La norma NEMA MG 00001 2024 introduce actualizaciones clave, incluyendo nuevos motores de Diseño BE y CE con límites de corriente de rotor bloqueado definidos, aislamiento Clase N para uso a alta temperatura y requisitos revisados ​​de tiempo de pérdida. Añade niveles de eficiencia Super Premium alineados con IEC IE4, adopta las directrices IEC sobre variación de voltaje/frecuencia y amplía las capacidades de servicio para motores de carga/velocidad variable.

From the manufacturer’s perspective, a random-wound, 2300-volt motor represents a substantial reduction in manufacturing cost. For the service center, the challenge is to successfully rewind them while providing a reliable repair. Here are some techniques which will enhance your success rate.

Desde la perspectiva del fabricante, un motor de 2300 voltios con bobinado aleatorio representa una reducción sustancial en el costo de fabricación. Para el centro de servicio, el reto es rebobinarlos con éxito y ofrecer una reparación confiable. Aquí hay algunas técnicas que mejorarán su tasa de éxito.

This presentation stresses the importance of taking accurate winding data and explains and emphasizes the consequences of inaccurate data. One of the main benefits of this presentation is to improve ability to “get it right the first time” to avoid the added cost and time of another rewind to correct errors.

In addition to seal oil, some submersibles have an oil filled stator cavity. The oil in the stator cavity very efficiently transfers heat from the stator winding and core, and especially from the rotor, to the pump casing where convection carries it to the pumpage in which the pump is submerged. While the specifications for seal oil are fairly flexible, stator cavity oil has more constraints.

Además del aceite de sellado, algunas bombas sumergibles tienen una cavidad del estator llena de aceite. Este aceite transfiere de manera muy eficiente el calor desde el devanado y el núcleo del estator, y especialmente desde el rotor, hasta la carcasa de la bomba, donde la convección lo lleva al líquido de bombeo en el que está sumergida. Si bien las especificaciones para el aceite de sellado son bastante flexibles, el aceite de la cavidad del estator tiene más restricciones.

This presentation reviews procedures that explain how to identify unmarked leads of three-phase motors with one or two windings.

When a core loss test reveals localized hot spots, or visual inspection identifies physical damage, the ability to repair the damage in a cost-effective manner means the difference between repair or replacement.