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.

En el actual entorno competitivo cada vez mayor, los usuarios finales buscan centros de servicio de máquinas eléctricas rotativas que aumenten su oferta de valor agregado. Una de las formas más fáciles para que un centro de servicios logre esto es efectuando una inspección minuciosa y detallada de los equipos que reciben para reparación. Los resultados de dicha inspección permiten mejorar la confiabilidad de los equipos que se logra a través de los resultados de la evaluación y las recomendaciones que ofrece el centro de servicio para prevenir fallas recurrentes y mejorar el tiempo medio entre fallas.

A special discounted collection of 11 webinar recordings focusing on AC motor electrical procedures.

Just $55 for EASA members!

This book was developed to help electric motor technicians and engineers prevent repeated failures because the root cause of failure was never determined. By using a proven methodology combined with extensive lists of known causes of failures, one can identify the actual cause of failure without being an “industry expert.” In fact, when properly used, this material will polish one’s diagnostic skills that would qualify one as an industry expert.

This article addresses electrical testing and inspection of installed 3-phase squirrel cage motors. The main purposes of testing installed electric motors are condition assessment for continued service or to diagnose suspected faults. The emphasis here will be on diagnostic electrical testing and interpretation, as well as physical inspection key points. Note: Most of the tests and inspections described in this article can also be performed on 3-phase wound rotor motors, and induction and synchronous generators.

Este artículo cubre las pruebas eléctricas y la inspección de motores trifásicos jaula de ardilla que han sido instalados. Los principales objetivos al probar los motores en el sitio de trabajo son: Evaluar su condición para garantizar su funcionamiento continuo odiagnosticar presuntos fallos. Aquíharemos énfasis en las pruebas y enla interpretación de los resultados, asícomo también, en la inspección física de los puntos clave. Nota: La mayoría de las prue­bas descritas también se pueden realizar a los motores con rotor bobinado y en los gen­eradores sincrónicos y de inducción. 

Filled with practical information, this 118-page handbook (3.5" x 6", 9cm x 15cm) makes a great “give-away” item for your customers and potential customers! Buy this great resource as is OR imprint your company logo and information on the cover to turn it into a great marketing piece for your salespeople!

The power factor tip-up test is commonly used as a quality measurement for new coils and windings manufactured for AC motors and generators rated 6 kV and higher. It can also be useful in the rewind shop to verify the quality of a newly-installed coil system including the effectiveness of VPI processing.

La prueba de volcado del factor de potencia se usa comúnmente como una medida de calidad para bobinas y devanados nuevos fabricados para motores de CA y generadores con clasificación de 6 kV y más. También puede ser útil en el taller de rebobinado para verificar la calidad de un sistema de bobina recién instalado, incluida la efectividad del procesamiento de VPI.

This article demonstrates the suitability of resin rich insulation systems for hydro generator service and highlights the advantages of being able to introduce remedial measures during the life of the winding to address issues and ensure that acceptable winding life is achieved 

This version of the EASA Motor Rewind Database software takes a large leap forward with the data that it provides members. Most notably, it now has the ability to connect to a live, ever-expanding online database of more than 250,000 windings. This live database will be continuously monitored, updated and corrected as needed by EASA’s Technical Support Staff.

This article looks at an issue encountered with new air-cooled machines rated at 13.8 kV that generated large quantities of ozone and had very high partial discharge levels. The basic problem with the windings in these machines was incorrect spacing of the end turns and the main leads. There was also a lack of space between the series and group connections in the windings. 

Recientemente trabajé en una máquina nueva de 13.8 kV de tensión nominal, enfriada por aire,   que pro-ducía grandes cantidades de ozono y tenía grandes niveles de descargas parciales. El problema básico con  los bobinados de esta máquina era  el espacio incorrecto entre las cabezas de bobina y los cables  de salida prin-cipales. También había poco espacio entre las series y las conexiones entre los  grupos del bobinado.

This recording covers theory of operation, inspection, operation and troubleshooting tips for AC generators and alternators. For the supervisor, field service technician or service center personnel, generators can present unique challenges.

Service centers routinely check the shaft extension runout of motors and generators. When there are issues associated with them, or when applicable, the coplanarity of the mounting feet and the amount of end foat of horizontal sleeve bearing motors and generators are checked.

This paper, presented at the 2014 EASA Convention, covers theory of operation, inspection, operation, and troubleshooting tips for AC generators.

We begin this article by clarifying the terms "alternator" and "generator." Both terms refer to a machine that converts mechanical to electrical power. An alternator is a synchronous machine that converts mechanical to AC electrical power. A generator is a more general term and is a machine that converts mechanical to electrical power, either AC or DC. An alternator is always a generator, but not vice-versa. Our focus in this article will be on 3-phase alternators. However, much of the information provided also applies to single-phase alternators and single- or three-phase generators. Key steps are:

• Identifying the leads
• Determining lead wire size
• Determining the internal connections
• Current density
• Winding changes
• Voltage changes

In the April 2007 issue of CURRENTS, we covered surge testing anomalies, specifically for AC windings. The surge test can be used for DC windings as well. It can be a useful tool for evaluating armatures and some DC fields. A note of caution: If a winding does not have a minimum insulation resistance per ANSI/EASA AR100-2006, it is not safe to apply an overpotential test (surge or high potential). Surge testing shunt fields may not provide meaningful results if the surge pulse decays too quickly - if it dissipates through only the first few hundred turns. To obtain a test voltage high enough to test every turn would require too high a voltage. That high voltage would overstress the groundwall insulation.

There are a number of different types of DC generators: shunt, series and compound, each of which can be separately or self-excited. A DC generator is built and designed exactly the same as a DC motor,and can be run as such. Regardless of the type, there are a number of reasons why a generator won't produce the correct voltage, or any voltage at all.

The paper "Wind Generators: Unique Repair Tips" by Chuck Yung, presented at the EASA Convention 2006, provides valuable insights into the repair and maintenance of wind generators, highlighting opportunities for improvement in insulation strength and mechanical construction. Wind power is rapidly growing in North America, with significant installations in 2005 and projections for continued growth. Most commercial wind generators in North America are rated between 660 kW and 1.5 MW, although larger units exist. The paper emphasizes the importance of cost-effective repairs due to the high expense of crane services required to remove generators from tall towers.

The purpose of this article is to provide a simplified explanation of how induction generators work, and what problems we might expect when repairing them. We owe it to our customers to help them avoid these pitfalls. If not, a generator may come back as an unjustified warranty claim.

An alternator is a converter: It converts mechanical energy into alternating electrical current. It's a generator: It generates (creates) alternating electrical current out of mechanical energy. How's it doing that? It's magic! Nah, not at all. This article will show you how.

The case study in this article demonstrates that EASA members have great opportunities to develop and improve customer relationships by helping them solve their application problems.