Chuck Yung
EASA Senior Technical Support Specialist

Although the earliest practical DC motor was built by Moritz Jacobi in 1834, it was over the next 40 years that men like Thomas Davenport, Emil Stohrer and George Westinghouse brought DC machines into industrial use.

It’s inspiring to realize that working DC motors have been around for over 160 years. For the past century, DC machines over 30 or 40 kW have been cooled in the same manner – by mounting a squirrel cage blower directly over the commutator.

Tom Bishop, P.E.
EASA Senior Technical Support Specialist

Determining the source of noise in a motor is often much more challenging than correcting it. However, a methodical approach to investigating the noise can narrow down the possible causes and therefore make it easier to resolve the noise issue. In this session we will address the causes and characteristics of the primary sources of noise in AC motors. Specific topics to be addressed:  

• Magnetic noise (aka “electromagnetic noise” or “electrical noise”) 
• Mechanical noise 
• Windage noise 
• Guidance for reducing or eliminating the intensity of these noise sources

This webinar recording is intended for mechanics, supervisors and testing technicians.

Chuck Yung
EASA Senior Technical Support Specialist

Most service centers balance rotors routinely, with few surprises in the process. There are even technicians who balance rotors so well that the highest velocity readings on the test bed are normally under 0.01 inch/second. It is a great indication of quality when a customer swears that a motor has never run that smoothly. Most of us do not balance fans nearly as often as rotors. The fan balancing tips in this article should be helpful. We'll start with a basic explanation of balancing and then get into balancing tips for fans. Many of these are also applicable to impellers, large sheaves and other rotating parts our customers may ask us to balance.

Topics covered include:

• Balancing basics
• Differences when balancing fans
• Building a balancing mandrel
• Alternative solutions
• Other factors that affect balancing

Chuck Yung 
EASA Technical Support Specialist 

Most of us involved in the repair of electrical equipment have a good understanding of how an electric motor works–especially the stator and ro­tor. But the fan can appear deceptively simple. Fans are pretty interesting, once we learn a few “affinity laws”—rules that also apply to blowers and impellers. This article will review some basic facts about fans that explain how small changes to a fan can make a BIG difference in the following critical areas: 

• Volume of air moved
• Static pressure
• Load
• Losses (efficiency)

These rules hold true for fan applications, im­pellers in pumping applications, and cooling fans on electric motors. When applied to the external fan of a TEFC (IP-54) motor, these rules offer some real opportunities for efficiency improvement. 

En toda reparación mecánica, la capacidad para desmontar, reparar y volver a montar el motor de forma apropiada sin dañar innecesariamente ninguna de sus piezas es fundamental. Esto suena sencillo, sin embargo, durante el proceso de desarme se cometen demasiados errores costosos.

Si todos los motores entraran “como nuevos”, la tarea sería más simple, aunque esto no sería garantía de que el montaje del motor fuera adecuado.

Cuando un centro de servicio recibe un pago por reparar un equipo, quiere que este permanezca en funcionamiento, ya que, si el equipo falla dentro del período de garantía, deberá asumir el costo de volver a repararlo. Por lo que tiene sentido realizar la reparación correcta la primera vez.

Los procedimientos de reparación, así como los propios motores, son afectados por los cambios en la tecnología. Este libro intenta incluir las últimas tecnologías comprobadas. En muchos casos, los métodos de reparación tradicionales aún pueden ser la alternativa más práctica. Las opciones presentadas a lo largo de este libro están destinadas a ayudar a los técnicos a seleccionar el método de reparación correcto, reconociendo que la decisión final recae en el propietario del equipo.

Algunas veces los métodos de reparación pierden popularidad, no porque aparezcan métodos mejores sino debido a técnicas deficientes. Otros métodos de reparación son adecuados para algunas aplicaciones, pero no para otras. Es trabajo del reparador decidir cuál será el mejor método para cada caso.

Este libro se encuentra dividido en secciones para los componentes básicos del motor con métodos de reparación y consejos dispersos por todas partes. Donde resulte práctico, se discuten también las causas de fallo. Esto ayudará a los técnicos a seleccionar el método de reparación más apropiado para cada aplicación en particular. La información presentada se basa en publicaciones de EASA y en revistas técnicas y literatura suministrada por fabricantes de motores, proveedores y centros de servicio establecidos.

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Tabla de contenido

• Terminología del motor
• Aplicaciones del motor y encerramientos
• Procedimientos de inspección y prueba
• Consejos para desmontar motores
• Rodamientos
• Alojamientos de rodamientos, orificios de eje, sellos y ajustes
• Ejes
• Rotores
• Ensamble del motor
• Accesorios y cajas de conexiones del motor
• Dinámica del motor
• Vibración y geometría del motor
• Corrientes por el eje/rodamientos
• Consideraciones especiales para motores a prueba de explosión
• Fallos en las componentes mecánicas
• Reparaciones misceláneas

Esta obra contiene muchas sugerencias sobre el manejo apropiado de las diferentes partes de un motor para minimizar los daños durante el proceso de reparación. Sin embargo, es imposible desarrollar un listado que las incluya todas.

En cambio, el principio básico de tomarse el tiempo para usar la herramienta adecuada y por lo general el procedimiento apropiado guiará a los técnicos por el camino correcto.

The purpose of this guide is to provide repair/rewind practices and tips that will help service center technicians and motor winders maintain or increase the efficiency, reliability and quality of the motors they repair.

Some of the included procedures derive directly from the 2019 and 2003 rewind studies by EASA and AEMT of the impact of repair/rewinding on motor efficiency. Others are based on the findings of an earlier AEMT study [1998] of small/ medium size three-phase induction motors and well-established industry good practices . 

The procedures in this guide cover all three-phase, random-wound induction motors. Much of the guide also applies to form-wound stators of similar sizes. 

(Note: This guide provides many specific procedures and recommendations. Alternative practices may accomplish the same results but must be verified.)

Download a FREE PDF using the link below or buy printed copies in EASA's Online Store

 

Table of Contents Overview

• Terminology
• Energy losses in induction motors
• Motor repair processes
  • Preliminary inspection
  • Dismantling the motor
  • Removing the old winding and cleaning the core
  • Rewinding the motor
  • Reassembling the motor
  • Confirming the integrity of the repair

WARNING: HAZARDOUS AREA MOTORS Some elements of this Good Practice Guide To Maintain Motor Efficiency, particularly those concerning changes to windings, do not apply to hazardous area/explosion-proof motors (e.g., UL, CSA, IECEx). Do not use this guide for those types of motors.

El propósito de esta guía es suministrar prácticas y consejos de reparación/rebo­binado que ayudarán a los técnicos y a los bobinadores del centro de servicios a conservar o aumentar la eficiencia, confiabilidad y calidad de los motores que reparan.

Algunos de los procedimientos incluidos derivan directamente de los estudios sobre el impacto de la reparación/ rebobinado en la eficiencia del motor realizados por EASA y AEMT en los años 2003 y 2019. Otros se basan en los hallazgos del estudio previo efectuado por AEMT [1998] en motores trifásicos pequeños/medianos y en las buenas prácticas industriales bien establecidas.

Los procedimientos de esta guía cubren todos los motores trifásicos de inducción de alambre redondo. Mucha información también aplica a motores con bobinas preformadas (pletina o solera) de tamaños similares.

(Nota: Nota: Esta guía proporciona muchas recomendacio­nes y procedimientos específicos. Se pueden lograr los mismos resultados con otras prácticas, pero deberán ser verificadas.)

Descargue un PDF GRATIS utilizando el link.

 

Tabla de Contenido

• Terminología
• Pérdidas de energía en los motores de inducción
• Procesos de reparación del motor
  • Inspección inicial
  • Desmontaje del motor
  • Remoción del antiguo bobinado y limpieza del núcleo
  • Rebobinado del motor
  • Montaje del motor
  • Confirmando la integridad de la reparación

ADVERTENCIA: MOTORES PARA TRABAJAR EN UBICACIONES PELIGROSAS Algunos elementos de esta Guía de Buenas Prácticas para Conservar la Eficiencia del Motor, especialmente los relativos a los cambios en los bobinados, no aplican a motores que trabajan en zonas peligrosas/a prueba de explosión (ej., UL, CSA, IECEx). No use esta guía para este tipo de motores.

Often an overhung fan is balanced in a single plane, only to find that the vibration has shifted to the outboard bearing. Attempts to use standard two-plane techniques may result in calculated correction weights that are very large and produce poor results. There are more effective ways to approach this common problem. This presentation shows a methodical approach and techniques for tackling this difficult balancing problem.

Target audience: This presentation is intended for field service balancing technicians, supervisors and managers.

Eugene Vogel
EASA Pump & Vibration Specialist

On occasion, service centers are asked to balance fan blades that are designed for an overhung mounting. The fan blade may be received mounted on the shaft, or without any shaft. The decision has to be made about how to mount the rotor in the balancing machine. One solution is to fabricate a mandrel to balance the fan blade between the machine pedestals. The other alternative is to mount the fan blade on the end of the shaft in an overhung configuration, with the fan blade outboard of both balancing machine pedestals. This would be the more expedient method if the fan blade is already mounted on the shaft in the overhung configuration.

As long as the fit of the fan blade to the shaft doesn’t change (when using a mandrel), it can be mounted in either configuration for balancing without affecting the results. If the fan blade is balanced in one configuration, it is balanced for the other. 

How the fan blade is mounted doesn’t change the balance, as long as the fit to the shaft doesn’t change. So the question is, “Which is easiest?” Often it is easiest to mount the rotor in the overhung configuration, but balancing in that configuration presents some challenges. Those challenges are addressed here.

This version of Principles of Medium & Large AC Motors manual is now available to address applicable IEC standards and practices. This 360-page manual was developed by industry experts in Europe along with EASA's engineering team. (The "original" version of this book based on NEMA standards remains available as a separate document.)

This manual includes drawings, photos and extensive text and documentation on AC motors, including how they work, information on enclosures, construction on components and applications. Many of the principles included apply to all AC motors, especially those with accessories that are associated with larger machines in the past (such as encoders, RTDs, thermostats, space heaters and vibration sensors).

While the manual covers horizontal and vertical squirrel-cage induction motors in the 37 to 3,700 kW (300 to 5,000 hp) range, low- and medium-voltage, most of the principles covered apply to other sizes as well. 

This valuable instructional/resource manual is available in printed and downloadable versions, and focuses primarily on IEC motors.

Sections in the manual include:
(Download the PDF below for the complete Tables of Contents)

• Motor nomenclature & definitions
• Motor enclosures
• Typical motor applications
• Safety & handling considerations
• Basic motor theory
• Motor standards
• Stators
• Squirrel cage rotors
• Shafts
• Bearings & lubrication
• Motor accessories & terminal boxes
• Test & inspection procedures
• Motor alignment, vibration & noise
• Storage procedures
• Synchronous machines

BUY A COPY FOR YOUR OFFICE

PRINTED BOOK DOWNLOADABLE PDF

This book is also available focusing on NEMA Standards — in both English and Español.

NEMA - English NEMA - Español

Chuck Yung
Especialista Sénior de Soporte Técnico de EASA

Aunque el primer motor de C.C. práctico fue construido por Moritz Jacobi en 1834, fue durante los 40 años siguientes que hombres como Thomas Davenport, Emil Stohrer y George Westinghouse fabricaron máquinas de C.C. para uso industrial.

Es inspirador darse cuenta que los motores de C.C. han estado trabajando por más de 160 años. Durante el siglo pasado, las máquinas de C.C. con potencias por arriba de los treinta o cuarenta kW han sido refrigeradas de la misma forma, montando un soplador de aire de jaula de ardilla directamente en el colector.

9 presentations

$45 for EASA members

 

A special discounted collection of 9 webinar recordings focusing on a wide variety of vibration, balancing and alignment topics.

Once purchased, all 9 recordings will be available on your "Downloadable products purchased" page in your online account.

Downloadable recordings in this bundle include:

An Overview of Vibration Tolerances
Presented August 2019

When it comes to machine vibration, “how much is too much” depends on a number of factors. Knowing which standard and/or tolerance applies requires a working knowledge of the standards and some basics of vibration terminology. This  presentation provides an overview of where and how NEMA, IEC, ISO and Hydraulic Institute standards may apply to machines commonly encountered in EASA service centers.

• NEMA, IEC, ISO and Hydraulic Institute standards
• Basic vibration terminology
• What standard applies?

Target audience: Service center managers, engineers, in-shop and field service technicians can benefit from a clearer understanding of vibration standards and terminology.

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Basics of Machinery Foundations and Bases
Presented November 2012

A faulty machine foundation or base can lead to excessive vibration and premature failure. This presentation explains the fundamentals of machinery foundation construction and how to identify and troubleshoot machine base problems, including basic vibration techniques and ODS analysis.

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Fundamentals of Shaft Alignment
Presented November 2012

Automatic alignment instruments are no substitute for the underlying process of aligning direct-coupled machines. This presentation explains the simple calculations that govern the alignment process. That understanding will allow technicians to use any alignment tool more effectively and deal with issues that confound the process.

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Shaft Alignment
Presented March 2016

This webinar recording provies a straightforward look at the simple relationship between shaft centerlines that is known as shaft alignment. Bypassing the common discussion of laser and manual instruments, this presentation gets to the heart of the shaft alignment process. Topics covered will include:

• Fundamental concepts
• How to visualize machine case position
• Practical solutions for moving machine cases
• Applying tolerances
• The foot-base-foundation connection

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ANSI's New Shaft Alignment Standard
Presented July 2018

This presentation introduces you to ANSI's new shaft alignment standard. Topics covered include:

• A discussion of alignment Quality grades, AL 1.2, AL 2.2, AL 4.5
• Shaft alignment tolerances
• Issues affecting measurements
• Conditions affecting alignment stability

Target audience: This presentation benefits service center technicians and supervisors looking to improve shaft alignment knowledge and skills. 

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How to Balance Overhung Fans
Presented October 2011

Often an overhung fan is balanced in a single plane, only to find that the vibration has shifted to the outboard bearing. Attempts to use standard two-plane techniques may result in calculated correction weights that are very large and produce poor results. There are more effective ways to approach this common problem. This presentation shows a methodical approach and techniques for tackling this difficult balancing problem.

Target audience: This presentation is intended for field service balancing technicians, supervisors and managers.

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Vibration on Belt Driven Machines
Presented June 2013

This presentation focuses on:

• Identifying belt vibration
• Identifying pulley pitch line run-out vibration
• Other vibration sources
• ODS analysis

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The FFT (aka Spectrum): What It Is and Ways to Use It
Presented July 2012

This presentation examines:

• How the spectrum is generated from the vibration signal
• The effect of f-max ad resolution settings
• Averaging techniques
• Scaling and demodulation

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Vibration Problems on Vertical Motors and Pumps
Presented December 2010

When motors are installed on top of vertical pumps, high vibration is a common problem. The problem may be mechanical, hydraulic or structural.

This presentation provides an understanding of the nature of this style pump and the various forces essential to diagnosing and correcting vibration problems on vertical pump motors.