11 presentations

$55 for EASA members

 

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

Once purchased, all 11 recordings will be available on your "Downloadable products purchased" page in your online account.

Downloadable recordings in this bundle include:

The Basics: Motor Repair Burnout Procedures
Presented October 2016

• Interlaminar insulation materials / properties of AC stators
• Core testing before and after
• Processing equipment, controls and records

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The Basics: The Why and How of Core Testing
Presented October 2016

• The reasons for performing core testing and why they are important
• An explanation of the two core testing methods:
• Loop testing
• Use of a core tester
• How to properly perform a core test
• How to assess the results
• Stator Core Testing: Know What You Have Before You Wind It

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Stator Core Testing: Know What You Have Before You Wind It
Presented April 2017

This presentation covers:

• The importance of the stator core test 
• Simple theory to share with technicians and customers 
• Practical approach for testing small stators demonstrated 
• Eliminating pen + paper; loop test calculations for any device 
• Assessing the results

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High Potential Testing of AC Windings
Presented December 2019

High-potential testing is routinely used to assess the ground insulation of AC stator windings in-process, after completion of a rewind and post-delivery. This webinar covers:

• Differences between AC and DC high-potential tests
• Sizing AC test sets when testing large windings
• What relevant standards address (and what they don’t)
• Communicating test requirements to all stakeholders
• When to test and at what levels
• How to evaluate results

Target audience: Beneficial for service center managers, supervisors and technicians responsible for high-potential testing.

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Squirrel Cage Rotor Testing
Presented October 2014

Determining whether or not a squirrel cage rotor is defective is an issue that is a challenge to every service center as there is often no simple way to determine the integrity of a rotor. The primary focus of this session is to describe many of the available tests that can be utilized in the service center or at the motor installation site. In addition to conventional squirrel cage rotor testing methods such as the growler test, techniques that will also be covered are the use of a core loss tester, high current excitation, and spectrum analysis of vibration.

Target audience: This presentation will be most useful for service center and field technicians with at least 2 years experience, service center supervisors and managers, engineers, or anyone with previous experience dealing with suspected open rotor issues.

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Evaluating High No-Load Amps of Three-Phase Motors
Presented December 2011

This presentation focuses on the steps to take before rewinding to avoid the undesirable situation of high no-load motor amps after the rewind.

The presentation covers the following steps that should be performed on every AC stator rewind:

• Inspect the stator bore and rotor outside diameter for evidence of machining or damage
• Record the original winding data exactly as found
• Verify the winding data
• Test the stator core before and after rewinding removal

Target audience: This is most useful for service center mechanics and winders with any level of experience, and service center supervisors and managers.

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Insulation Technology Improvements and the Repair Market
Presented July 2019

Most modern rotating electric machines operate on the same principles their predecessors have for 100+ years. However, improvements in materials technology over that time have allowed for increasingly greater power density in machine design.

There is a natural time lag between OEM technology improvement and repair of equipment containing that technology. This session will explore some of these improvements and their implications for service centers attempting to provide a quality repair.

Target audience: This webinar will be appropriate for service center managers and technicians responsible for rewind activities.

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Motor Temperature Rise and Methods to Increase Winding Life
Presented December 2018

This webinar discusses:

• Temperature rise: Method of detection, Insulation class, Enclosure, and Service Factor
• Increasing winding life: Insulation class, Cooling system, and Winding redesign

Target audience: This will be most useful for service center engineers, supervisors, managers and owners. The content will also be beneficial for mechanics and winders.

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Air Gap: What It Is, What Does It Do, and Why Is It Important?
Presented October 2019

The physical air gap between the rotor or armature and the stator or field frame is complex and plays a critical role in the performance of AC and DC machines. Most repairers do not realize how little they understand about this subject.

This webinar explains the role air gap plays in AC motor performance, how to recognize the symptoms of an uneven air gap, and share corrective measures. For DC machines, this webinar will cover the distinctly different role of the field air gap as opposed to the air gap of the interpoles.

• Air gap tolerance of AC machines
• Air gap tolerance of DC fields and interpoles
• Allowable runout of rotor / armature
• Recognizing the signs of air gap anomalies
• Corrective actions

Target audience: This webinar recording is of benefit to managers, supervisors, winders, mechanics and field service personnel.

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Troubleshooting AC Generators & Alternators
Presented May 2015

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. Topics covered include:

• Theory of operation
• Testing tips
• Stator winding cautions
• How to interpret the exciter motor connection
• In-shop and on-site testing methods
• How to test the voltage regulator
• How to test a generator without a regulator

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Core Repair and Restack Techniques
Presented April 2014

This webinar teaches:

• How to repair damaged stator cores and how to know when a restack is necessary.
• There are often cases when repairs can be accomplished without a labor intensive restack.
• When a restack is required, there are pitfalls to watch out for to avoid problems with geometry, vibration and core losses.

Target audience: This presentation is useful to the supervisor, winder and sales personnel who interact with the end user.

Chase Fell
Precision Coil and Rotor

Un aislante ideal no permite el flujo de la corriente de fuga. El factor de potencia de un aislante se define como el coseno del ángulo de fase entre el voltaje y la corriente. En un aislante ideal, la corriente adelanta al voltaje exactamente 90 grados y en este sistema ideal el factor de potencia sería cero. Los sistemas de aislamiento de las bobinas de los motores y generadores eléctricos tienen pérdidas inherentes que causan el flujo de corrientes capacitivas y resistivas (Ver Figura 1). Para estos aislamientos, el factor de potencia no puede ser cero. 

El factor de potencia tip-up (FP) se utiliza comúnmente para medir la calidad de las bobinas nuevas y devanados fabricados para motores y generadores de C.A. de 6 kV o tensiones superiores. En los sistemas de aislamiento modernos de los devanados estatóricos, el factor de potencia y el factor de disipación dieléctrica son casi los mismos (Ver Figura 2). La prueba de FP tip-up puede ser útil para verificar la calidad del proceso de fabricación del bobinado, el comportamiento del material aislante, la consolidación de los conductores, la uniformidad del encintado del muro aislante y la condición del curado de la resina. Una vez el sistema de aislamiento alcance el voltaje de inicio de efecto corona (CIV), la descarga parcial (DP) cortocircuitará efectivamente algo de la capacitancia del aislamiento y el factor de potencia aumentará. La prueba FP aplica a bobinas individuales tratadas con impregnación por presión y vacío (VPI) y bobinas resin-rich, así como también a bobinados completamente curados. La prueba de factor de potencia tip-up no aplica a pruebas en banco de bobinas VPI sin curar (verdes) o para evaluar bobinados completos pre-procesados VPI. 

En los centros de servicio, la prueba de factor de potencia tip-up puede ser útil para verificar la calidad de un sistema de bobinas recién instalado, incluyendo la eficacia del proceso VPI. La prueba FP de los bobinados en servicio puede establecer una medida de referencia para el mantenimiento por análisis de tendencias. Esta prueba FP en servicio puede identificar potencialmente el envejecimiento del muro aislante, ya que la capacitancia entre el conductor de cobre y el núcleo del estator, generalmente se reduce a medida que se presenta separación de las cintas (delaminación) y/o burbujas de aire en el aislamiento (voids), entre las bobinas y el núcleo. La separación de las cintas de aislamiento normalmente aparece o se acelera por el envejecimiento térmico o mecánico del bobinado. La separación de las cintas y/o las burbujas de aire en el aislamiento pueden ocasionar descargas parciales y el fallo prematuro del sistema de aislamiento.

Cyndi Nyberg 
Former EASA Technical Support Specialist 

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. 

Let’s start with the basics of how a DC generator works. When the armature is rotated, the magnetism from the fields produces a voltage in the armature. If the generator is self-excited, then the small voltage produced in the armature in turn is supplied back to the fields, which induces current in the fields. 

Richard Huber, P. Eng.
Richard Huber Engineering. Ltd
North Vancouver, BC
Canadá
Miembro del Comité Técnico de Servicios

Introducción
Recientemente trabajé en una máquina nueva de 13.8 kV de tensión nominal, enfriada por aire,   que producía 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 principales. También había poco espacio entre las series y las conexiones entre los  grupos del bobinado.

DESCRIPTION
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 custom brand your company logo and information on the cover to turn it into a great marketing piece for your salespeople!

BUY COPIES OF THIS HANDBOOK

TABLE OF CONTENTS

MOTOR DATA–ELECTRICAL
Standard Terminal Markings and Connections
DC Motors and Generators (NEMA & IEC Nomenclature)
Field Polarities of DC Machines
General Speed-Torque Characteristics
Full-Load Efficiencies of Energy Efficient Motors
Full-Load Efficiencies of NEMA Premium™ Efficient Motors
Effect of Voltage Variation on Motor Characteristics
Power Supply and Motor Voltages
Effect of Voltage Unbalance on Motor Performance
Starting Characteristics of Squirrel Cage Induction Motors
Allowable Starts and Starting Intervals

MOTOR DATA–MECHANICAL
Suffixes to NEMA Frames
NEMA Frame Assignments–Three-Phase Motors
NEMA Frame Dimensions–AC Machines
IEC Mounting Dimensions–Foot-Mounted AC and DC Machines
IEC Shaft Extension, Key And Keyseat Dimensions–Continuous Duty AC Motors (Inches)
NEMA Shaft Extension And Keyseat
Dimensions–Foot-Mounted DC Machines (Inches)
NEMA Frame Dimensions–Foot-Mounted DC Machines (Inches)
NEMA Frame Dimensions–AC Machines (mm)
IEC Mounting Dimensions–Foot-Mounted AC and DC Machines (mm)
IEC Shaft Extension, Key and Keyseat Dimensions–Continuous Duty AC Motors (mm)
NEMA Shaft Extension and Keyseat Dimensions–Foot-Mounted DC Machines (mm)
NEMA Frame Dimensions–Foot-Mounted DC Machines (mm)

MOTOR CONTROLS
Power Factor Improvement of Induction Motor Loads
Capacitor kVAR Rating for Power-Factor Improvement
Full-Load Currents–Motors
Maximum Locked-Rotor Currents–Three-Phase Motors
NEMA Code Letters for AC Motors
Starter Enclosures
NEMA Size Starters for Three-Phase Motors
NEMA Size Starters for Single-Phase Motors
Derating Factors for Conductors in a Conduit
Allowable Ampacities of Insulated Conductors
Motor Protection Devices–Maximum Rating or Setting

TRANSFORMERS
Full-Load Currents for Three-Phase Transformers
Full-Load Currents for Single-Phase Transformers
Transformer Connections

MISCELLANEOUS
Temperature Classification of Insulation Systems
Resistance Temperature Detectors.
Thermocouple Junction Types
Dimensions, Weight and Resistance: Solid Round Copper Wire (AWG and Metric)
Square Bare Copper Wire (AWG)
Insulation Resistance and Polarization Index Tests
Properties of Metals and Alloys

USEFUL FORMULAS AND CONVERSIONS
Temperature Correction of Winding Resistance
Temperature Correction of Insulation Resistance.
Formulas for Electric Motors and Electrical Circuits.
Motor Application Formulas
Centrifugal Application Formulas
Temperature Conversion Chart
Conversion Factors
Fractions of an Inch–Decimal and Metric Equivalents

Richard Huber, P. Eng. 
Richard Huber Engineering, Ltd. 
North Vancouver, BC
Canada 
Technical Services Committee Member

Introduction
Recently I worked on 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.

Spacing requirements
The spacing suggested here is a guide only and original equipment manufacturers (OEMs) and service centers may have their own guide for such values. It should be noted, how­ever, that if spacing is much reduced from that suggested here, there is a real risk that partial discharge activity will develop in the winding.

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

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. A common point about all three of these dimensions is that they are checked with the machine assembled; that is, no disassembly is required. There are many other mechanical tolerances associated with motors and generators, such as bearing fits. However, the focus of this article will be the three tolerances just mentioned. Rather than referring to both electric motors and generators, for brevity the term “machine” will be used.

Topics covered include:

• Shaft extension runout tolerance
• Coplanarity of mounting feet tolerance
• End float

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

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.

Chase Fell
Precision Coil and Rotor

An ideal insulator allows no leakage current to flow. The power factor of an insulator is defined as the cosine of the phase angle between voltage and current. For an ideal insulator, the current leads the voltage by exactly 90 degrees and the power factor for this ideal system would be zero. Coil systems in electric motors and generators have inherent losses causing capacitive and resistive current flow. For this insulation, the power factor cannot be zero. 

The power factor (PF) 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. For modern stator winding insulation systems, the power factor and the dielectric dissipation factor are very nearly the same. PF tip-up testing can be useful to verify the quality of the winding manufacturing process, insulation material performance, consolidation of conductors, uniformity of groundwall taping and state of resin curing. Once an insulation system reaches corona inception voltage (CIV), partial discharge (PD) will effectively short out some of the capacitance of the insulation and the power factor will increase. PF testing is applicable to individual vacuum pressure impregnation (VPI) coils and resin-rich coils as well as cured complete windings. Power factor tip-up testing is not applicable for bench testing of green VPI coils or evaluating pre-processed complete VPI windings. 

The power factor tip-up test can be useful in the rewind shop to verify the quality of a newly-installed coil system including the effectiveness of VPI processing. PF testing of in-service windings can set a baseline measurement for maintenance trending. The in-service PF tip-up test can potentially identify groundwall insulation aging since the capacitance between the copper conductor and the core is generally reduced as delamination and/or air pockets become present in the insulation between the coils and the core.

Por Tom Bishop, P.E.
Especialista Sénior de Soporte Técnico de EASA 

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. 

Por Steven Carbone
Miembro del Comité de Educación Técnica
Industrial Electro-Mechanics

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.

John Allen
Sheppard Engineering

Clachan Hydro Power Station (HPS) went into service in 1956. Clachan HPS is located on Scotland’s west coast about 40 miles north of Glasgow. The underground power station is at the head of Loch Fyne sea loch. See Figure 1. The tailrace discharges into the Fyne River, a salmon fishing river. Loch Fyne has a renowned fishery and seafood restaurant within a mile.

The 900 ft (275 m) head vertical shaft Francis turbine driven 50 MVA, 40 MW 428.6 rpm 11 kV generator was designed by English Electric. The generator stator was recored and rewound in 1984 by Peebles Field Services (acquired by Dowding & Mills in 1998).

During the 1984 rewind, the original split core stator was rebuilt as a complete annulus. And the Class B winding was replaced by a resin rich Class F epoxy winding. The turns were insulated with Samicaflex insulation tape and the slot cell would typically have been an S5 mica tape; this is a 180g/m2 epoxy mica tape on a glass fabric. The dielectric stress for the slot cell (wall) insulation was very conservative at 41.9 v/mil (1,650 v/mm).

The rewind used 5 mm (0.197”) epoxy glass wedges with Nomex 410 packing and 4 mm (0.157”) phenolic glass coil separators. The punched slot width was 22.15 mm (0.872”) which would typically have resulted in a built slot width of 21.8 mm (0.858”) and the specified slot cell width was 21.1 mm (0.831”).

As part of Scottish & Southern Electric (SSE) program of power station refurbishment, Clachan HPS was refurbished in 2000. The program included refurbishment of the generator stator with an option to rewind if the partial discharge levels could not be improved. 

Dowding & Mills refurbished the generator stator, re-insulated the rotor and replaced the DC exciter with a brushless excitation system. They also replaced the complete station control systems together with all the low voltage (LV) and high voltage (HV) electrical installations.

This valuable resource is available only to EASA Members.

Active and Allied members can download this software for FREE!

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. Using the online database guarantees you’ll have the most up-to-date information available at all times. If your computer does not have an Internet connection, the software will automatically switch to the static, local database that was included and loaded during installation. (Note: The local database does not receive updates.)

The database includes:

• Three-phase, single-speed AC motors
• Three-phase, multi-speed AC motors
• Single-phase AC motors
• DC motors & generators

Chuck Yung 
EASA Technical Support Specialist 

We have had several calls like this, due to renewed interest in using induction generators for wind generation. With induction wind generators, there are some critical factors that mean the difference between success and failure. These are application issues, and the ultimate responsibility rests squarely with the end-user. By the way, most of these issues are applicable to all induction generators, regardless of the prime mover.

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, and no one wants that. 

John Allen
Sheppard Engineering

La Central Hidroeléctrica de Clachan, comenzó a funcionar en 1956. Esta central subterránea se encuentra localizada en la costa oeste escocesa, a unas 40 millas del norte de Glasgow y en la cabecera del lago salado Loch Fyne. Ver Figura 1. El ducto de descarga vierte el agua dentro del rio Fyne, en el cual se pesca salmón. Loch Fyne cuenta en una milla con pesca reconocida y marisquerías de renombre.

La turbina Francis de eje vertical con salto de agua de 900 pies (275 m) que acciona un generador de 50 MVA, 40 MW 428.6 rpm 11 kV fue diseñada por English Electric. En 1984, el núcleo del estator fue reconstruido y el estator fue rebobinado por Peebles Field Services (adquirida en 1998 por Dowding & Mills).

Durante el rebobinado de 1984, el núcleo original fabricado en secciones, fue reconstruido totalmente en forma de anillo y el bobinado Clase B fue reemplazado por un bobinado epóxico resin-rich Clase F. Las espiras fueron aisladas con cinta Samicaflex y el aislamiento a tierra generalmente estaba fabricado con cinta de mica S5; esta es una cinta de mica de 180g/m2 sobre un tejido de fibra de vidrio. La rigidez dieléctrica del aislamiento a tierra (Pared de aislamiento) de 41.9 v/mil (1,650 v/mm) era muy conservadora.

Durante el rebobinado se utilizaron cuñas epóxicas de vidrio de 5 mm (0.197”) con un relleno de Nomex 410 y separadores de bobinas de vidrio fenólico de 4 mm (0.157”). El ancho de la ranura perforada era de 22.15 mm (0.872”), lo que normalmente habría dado lugar a un ancho de ranura construida de 21.8 mm (0.858”) y el ancho de la pared de aislamiento especificada era de 21.1 mm (0.831”).

Como parte del programa para el reacondicionamiento de centrales eléctricas de la Scottish & Southern Electric (SSE), La Central hidroeléctrica de Clachan fue reacondicionada en el año 2000. El programa incluía el reacondicionamiento del estator del generador con la opción de rebobinarlo, si no se podían mejorar los niveles de descargas parciales. 

Dowding & Mills reacondicionó el estator del generador, re-aislando el rotor y reemplazando la excitatriz de CC por un sistema de excitación sin escobillas. Ellos también cambiaron completamente los sistemas de control de la estación, conjuntamente con todas las instalaciones eléctricas de bajo y alto voltaje.

This book was developed to help electric motor technicians and engineers prevent repeated failures because the root cause of failure was never determined. There are numerous reasons for not pursuing the actual cause of failure including:

• A lack of time.
• Failure to understand the total cost.
• A lack of experience.
• A lack of useful facts needed to determine the root cause.

The purpose of this book is to address the lack of experience in identifying the root cause of motor failures. 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.

The book is divided into the various components of an electric motor. In addition to a brief explanation of the function of each component and the stresses that act upon them, numerous examples of the most common causes of failure are also presented.

For this second edition, the manual has been reorganized and updated with new information including a new approach to methodology, new case studies and a new section covering synchronous machine failures. This could not have been done without many contributions from EASA members and the Technical Education Committee. 

The all new “Root Cause Methodology” section goes into great detail explaining that effective root cause failure analysis must take place within the context of a practical problem-solving methodology or framework. It covers a modified Plan-Do-Check-Act process that emphasizes the importance of planning and the related problem-solving methodology components. This section also explains A3, a high-level reporting tool that is very effective for problem solving.

In addition, besides a systematic approach to problem solving, root cause failure analysis of motors and motor systems requires familiarity with contributing factors attributable to various kinds of applications, environments and industries. This includes how various stresses can affect motor components and the reciprocal impact the motor system may have on the motor. This section includes a table with a detailed summary of motor stresses. 

There also is a new section on “Synchronous Machine Failures” and an expanded “Case Studies” section. Readers are guided through eight case studies.

With 328 pages, the book provides extensive information, including a wide range of failures, the likely causes listed, and the methodology for confirming the probable cause of each failure. 

Members may purchase a printed manual and/or a PDF download. The printed manual is in black and white, while the download shows most of the failure photos in color.  

Sections in the manual include:

• Root Cause Methodology (all new)
• Bearing Failures
• Stator Failures
• Shaft Failures
• Rotor Failures
• Mechanical Failures
• DC Motor Failures
• Synchronous Machine Failures (all new)
• Accessory Failures
• Case Studies (expanded)
• References

This book is available as part of EASA's Root Cause Failure Analysis seminar.

BUY NOW
PRINTED COLOR BOOK DOWNLOADABLE PDF PRINTED COLOR BOOK & PDF

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DISCOUNTED BLACK & WHITE BOOKS!
Prices are now DISCOUNTED on remaining black & white books while supplies last! If you have already purchased a black & white manual and are interested in the color version, please contact EASA Customer Service (+1 314 993 2220).

B&W BOOK B&W BOOK & DOWNLOAD

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Cyndi Nyberg 
Former EASA Technical Support Specialist 

In the April 2007 issue of CURRENTS, we covered surge testing anomalies, speci.cally 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 .elds may not provide meaningful results if the surge pulse decays too quickly — if it dissipates through only the .rst 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 ground-wall insulation. 

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

We will 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.

Chuck Yung
EASA Senior Technical Support Specialist

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.

Several generators driven through gearboxes at a hydro site ran fine for years, until one excitor failed electrically. After being repaired and reinstalled, it performed well electrically but vibrated more than the other units. A few months later, a second generator experienced a bearing failure. The unit was repaired by the same service center, and it also vibrated after repair and reinstallation. By the time a third unit lost an excitor, the customer was looking for a different service center. Unfortunately, the results were the same. The customer pursued the issue.

All told, four shops worked on these generators, but none improved the vibration. Finally, the first shop got another try. This time, a new technician examined the problems encountered and listened to those who were involved previously. Just as important, he looked at the application itself: the generators had welded rib frames, covered by sheet-metal shrouds. They were a two-bearing style, with an overhung excitor. The generator was then repaired and installed using the procedures outlined by the technician - and ran smoothly. What did the technician do to correct the problems?

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. Topics covered include:

• Theory of operation
• Testing tips
• Stator winding cautions
• How to interpret the exciter motor connection
• In-shop and on-site testing methods
• How to test the voltage regulator
• How to test a generator without a regulator

Chuck Yung
EASA Senior Technical Support Specialist

This paper, presented at the 2014 EASA Convention, covers theory of operation, inspection, operation, and troubleshooting tips for AC generators. For the supervisor, field service technician or service center personnel, generators can present unique challenges. Topics covered include:

• Theory of operation
• Testing tips
• Stator winding cautions
• How to interpret the exciter rotor connection
• In-shop and on-site testing methods
• How to test the voltage regulator
• How to test a generator without the regulator

George Stratton 
G.E. Jones Electric Co., Inc. 
Amarillo, Texas 
Technical Education Committee Member 

We take so much for granted. The alarm clock buzzes and we make our way to the bathroom and turn on the light. We reach over and turn the water on and it’s there. We flip the switch on the electric razor. We really do take it all for granted. The en­ergy that flows through the wires to the switch that you flip comes from a device called an alter­nator. Yes, somewhere close to where you live is a power plant where that energy that makes the world go around is created.

Alternators come in all kinds of configura­tions. Your car or truck even has one. That’s right. An alternator is needed to charge the battery and provide electric power for your vehicle. If you have a recreational vehicle (my wife’s idea of really roughing it) you probably use a generator to power that air conditioner that would be tough to live without these days. This device is handy for watching TV, too.