Gene Vogel
EASA Pump & Vibration Specialist

Proper alignment of direct-coupled machinery is an essential element in reliability of a new or repaired machine (motor, pump, gear case, etc.). One common impediment to achieving proper alignment and smooth opera­tion is a “soft foot” condition. 

A soft foot occurs when all the feet of a machine case do not sit flat on the supporting base so that tightening the foot bolts causes distortion of the ma­chine case. The source of the soft foot could be a baseplate which is not flat or machine feet which are distorted. Not only does this make it difficult to align the machine, but the casing distortion may add additional load to the bearings and create internal mis­alignment between the rotating and stationary elements of the machine resulting in poor performance and increased vibration.

Kent Henry 
Former EASA Technical Support Specialist

In the power transmission indus­try, a fair amount of cast iron is used. Whether it’s for motors, pumps, or gear reducers, many use cast iron for the bulk of their structure. This variety of usage results in service opportunities involving the repair of cast iron components. 

Cast iron has a very high carbon content, so much so that the concen­trations of carbon form graphite flakes that result in a high resistance to wear. The drawback of cast iron is that the high carbon content also makes castings brittle. Examples of brittle castings are terminal boxes and fan covers. If a forklift operator rounded a corner a little wider than normal and bumped into the terminal box and fan cover of a Totally Enclosed Fan Cooled (TEFC) motor made from steel, the impact would bend the steel components. Steel is a fairly ductile material. The repair of these parts may Figure 1. Example of crack prepared for welding. and fully weld this side of the be limited to hammering out dents in the terminal box and fan cover. If the same collision happened with cast iron components, the damage would be quite different. They would likely be cracked or even break into pieces due to the brittleness. 

Jacob Snyder
Evans Enterprises, Inc.

When a modern temperature controlled (i.e., controlled pyrolysis) burnout oven is not available, the method described here can be used to process aluminum frame motors.

Jacob Snyder
Evans Enterprises, Inc.

El método aquí descrito se puede utilizar para procesar motores con carcasa de aluminio cuando no se tenga un horno moderno de quemado con temperatura controlada (es decir de pirolisis controlada).

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

Occasionally an end user wants to take a motor designed for horizontal mounting and use it in a vertical position. In this article, we will address some of the key mechanical factors that should be considered when applying a horizontal ball bearing motor in a vertical mounting position. Figure 1 illustrates a horizontal motor in a vertical shaft down position.

These key factors include:

• Axial thrust load capacity of bearing supporting rotor weight
• Rotor weight
• Weight of output shaft attachments
• Axial thrust from direct connected driven equipment
• Bearing lubrication paths
• Bearing lubricant retention
• Shaft up or shaft down orientation
• Ingress protection
• Locking axial thrust bearing

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

De vez en cuando un usuario final quiere utilizar un motor diseñado para montaje horizontal en posición vertical. En este artículo, trataremos algunos factores mecánicos clave que deben ser considerados cuando se utiliza un motor horizontal con rodamientos de bolas en una aplicación en la que trabaja en montaje vertical. La Figura 1 ilustra un motor horizontal en posición vertical con el eje hacia abajo.

Los factores clave incluyen:

• Capacidad de carga axial del rodamiento que soporta el peso del rotor.
• Peso del rotor
• Peso de los elementos acoplados al eje de salida
• Empuje axial de los equipos de impulsión acoplados directamente
• Trayectorias de lubricación de los rodamientos
• Retención del lubricante de los rodamientos
• Orientación del eje: Hacia abajo o hacia arriba
• Protección contra ingreso
• Fijación axial del rodamiento de empuje

REVISED September 2022!

The EASA Technical Manual, containing more than 900 pages of information specific to electric motor service centers, is available FREE to EASA members as downloadable PDFs of the entire manual or individual sections. The printed version is also available for purchase. Each of the 13 sections features a detailed table of contents.

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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

This book ws developed in conjuction with EASA's two-day Fundamentals of DC Operation & Repair Tips seminar.

This book is not meant to replace the many good texts that cover the theory and design of DC machines, but to supplement them. Its purpose is twofold: to help the technician understand DC machine theory without complex formulae; and in a larger sense, to record in one place the repair procedures and tips usually learned the hard way during a long career of DC machine repair. It may take a decade or longer for a technician to become proficient and knowledgeable. We hope this book will cut many years from that timeline.

The text begins with DC theory (no math, we promise!), and then follows the logical progression of a DC machine through the service center. Disassembly, inspection and testing are covered in the initial chapters. 

Subsequent chapters are organized around the main parts of a DC machine. The final chapters cover assembly, final testing and application issues. Sections focusing on components explain how those parts work, how they are made and how they can best be repaired.

Repair tips gleaned from EASA members’ decades of experience are liberally sprinkled throughout the book. While many texts about DC machines explain how they should work, this is the first (to our knowledge) to discuss all the exceptions that a repairer is liable to run across during a lifetime of working with DC machines. These might otherwise be labeled “lessons learned the hard way,” except that the reader can benefit from having all these special cases collected in one source. When possible, it is better to learn by reading than by trial and error; otherwise, the first encounter with a unique design can result in a painful “learning experience.”

A DC machine can be used interchangeably as a motor or generator, simply by changing the connection. Any DC motor can be driven and used to produce power, and any DC generator can be motorized to provide mechanical power. Although this text predominately refers to “motor;” the material applies to both motors and generators.

As with the other EASA publications—Principles of Large AC Motors, Mechanical Repair Fundamentals of Electric Motors, and Root Cause Failure Analysis—each section is designed to stand alone. The small amount of duplication is intentional, to save the reader from flipping back and forth between sections.

Table of Contents - (Download the complete Table of Contents)

• Nomenclature and Nameplate Information
• DC Motor Theory
• Disassembly and Inspection
• Testing
• Armatures
• Commutators
• Frames
• Ventilation and Accessories
• Motor Assembly and Final Testing
• On-Site Troubleshooting
• Failure Analysis

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Much has been written in EASA publications and elsewhere about the consequences of excessive temperature on a motor’s performance. We know that excessive temperature and moisture are the largest contributors to bearing and winding failures. Understanding the source of the increased temperature will help us to correct the problem and improve the machine’s life expectancy.

A chart included in this article illustrates the theoretical impact of increased temperature on the life of the motor insulation system. This chart only addresses the impact of thermal aging and not various other conditions that will affectthe motor’s life. In other words, it says that for every 10ºC increase in operating tem-perature, the expected life is reduced by one-half. Conversely, if we can re-duce the temperature of the motor by 10ºC, we can expect the life to double. Note that this is true at any point on the curve. However, there is the rule of diminishing returns: at some point the cost of designing and operating a motor to run cooler out-weighs the benefts of doing so.  Here we will explore some of the factors that con-tribute to increased temperature.

Topics covered include:

• Overload
• Ventilation
• Voltage
• Electrical steel (core iron)
• Current density
• Circulating currents
• Harmonics

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

The International Electrotechnical Commission (IEC) standard 60529, “Degrees of protection provided by enclosures (IP code),” addresses the degrees of protection for electrical machines (motors and generators). The “IP” acronym means “international protection” but is sometimes referred to as “ingress protection.” The IP code is commonly displayed on the nameplates of metric machines that are manufactured to IEC standards.

The NEMA MG1 Motors and Generators standards have adopted the IEC standards for IP designations. Although not prevalent on NEMA machine nameplates, the inclusion of the IP marking is becoming more common. In light of this, this article reviews IP code designations and examples of the IP codes for common electrical machine enclosures.

• IP characteristic letters
• IP characteristic numerals
• Typical IP codes

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Jim Bryan
EASA Technical Support Specialist (retired)

La placa de datos de un motor eléctrico revela mucha información valiosa acerca de la capacidad y desempeño de la máquina. Las normas NEMA MG1-2014 (National Electrical Manufacturers Association Motors and Generators 1) e IEC 60034-8 (International Electrotechnical Commission) brindan información que se debe incluir en la placa de datos para cumplir con las normas.

Por Gene Vogel
Especialista de Bombas y Vibraciones de EASA

Realizar una correcta alineación de las máquinas acopladas de forma directa es un elemento esencial para garantizar la confiabilidad de operación de una máquina nueva o reparada (motor, bomba, caja de engranajes, etc.). Uno de los impedimentos comunes para lograr una alineación adecuada y un correcto funcionamiento, es el denominado  "pie suave".

Fundamental to every good mechanical repair is the ability to disassemble, repair and reassemble the motor correctly without unnecessary damage to any of the motor parts. This sounds simple, and yet too many costly mistakes are made in this process of taking things apart. If every motor repaired was in “as new” condition, the task would be much simpler. But this would be no guarantee that the reassembly would be correct.

​There is usually an easy way and a hard way to remove and install parts. Brute force is seldom the easiest or the correct way. The old saying of “don’t force it, get a bigger hammer” is seldom the best way.

When a service center is paid to repair equipment, the service center wants it to stay in operation. If the equipment fails again—within the warranty period—the service center pays to repair it again. It makes sense to repair it correctly the first time.

In order to improve equipment, it is important to know how and where it operates. Without understanding why a motor fails, it is impossible to deliberately improve its mean time between failures.

To do this, there must be communication between the service center and the motor user. Not only does this help the repairer decide the best course of action, but it helps the user appreciate the professionalism of the service center.

Repair procedures, like motors themselves, are affected by changes in technology. This book attempts to include the latest proven technologies. Time-honored methods of repair, in many cases, may still be the most practical option. Options presented throughout this book are intended to help the technician select the appropriate repair method, recognizing that the ultimate decision rests with the equipment owner.

Repair methods sometimes fall into disfavor, not because better methods are introduced, but because of poor techniques. Other repair methods are well-suited to some applications but not to others. It is the job of the repairer to decide what is the best method for each case.

This book is divided into sections for basic motor components with repair methods and tips dispersed throughout. Where practical, reasons for failures are also discussed. These will aid the technician in selecting the most appropriate method of repair for each unique application.

The information presented draws from EASA publications, IEEE publications, technical journals and literature supplied by vendors, motor manufacturers and established service centers.

This book contains many suggestions on how to correctly handle the various parts of a motor during the repair process so as to minimize damage. However, it is impossible to develop an all-inclusive list. Instead, the basic principle of taking the time to use the correct tool and correct procedure will usually lead the technician down the right path. Always remember, if it has to be forced beyond reason, it might be that neither the proper tool or procedure is being used or something is wrong with the parts. Step back and ask “What am I overlooking?”

Table of Contents

1. Motor Nomenclature
2. Motor Applications and Enclosures
3. Test and Inspection Procedures
4. Motor Disassembly Tips
5. Bearings
6. Bearing Housing Repair, Shaft Openings, Seals and Fits
7. Shafts
8. Rotors
9. Motor Assembly
10. Motor Accessories and Terminal Boxes
11. Motor Dynamics
12. Vibration and Motor Geometry
13. Shaft/Bearing Currents
14. Special Considerations for Explosion-Proof Motors
15. Failures in Mechanical Components
16. Miscellaneous Repairs

This book is available as part of EASA's Fundamentals of Mechanical Repair seminar.

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Jim Bryan
EASA Technical Support Specialist (retired)

The nameplate of an electric motor reveals much valuable information about the capability and performance of the machine. NEMA MG1-2014 (National Electrical Manufacturers Association Motors and Generators 1) and IEC 60034-8 (International Electrotechnical Commission) provide information required to be included on the plate to conform to the standards. 

This varies by the type and size of the motor. For instance, rated field and armature voltages are required for direct current (DC) motors but obviously are not required for alternating current (AC) motors. A table is included that lists the basic requirements applicable to motors. Not all motors will comply with these requirements. These include motors built before the implementation of the standards or outside the jurisdiction of the standards agencies.  Some motors, such as synchronous and wound rotor motors, will have additional requirements. To cover all these is beyond the scope of this article.

Topics covered include:

• Identification
• Power
• Maximum ambient
• Speed
• Phase and voltage
• Code letter
• Design letter
• Efficiency and service factor
• DC motors
• Power factor
• Altitude

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

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PRINTED BOOK DOWNLOADABLE PDF

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

NEMA - English NEMA - Español

This presentation examines features, benefits and drawbacks of both conventional and alternative methods of cleaning electric motors.

Methods covered include:

• Immersion tanks
• Steam cleaning
• Parts-washing machines
• Pressure washers
• Abrasives
• Ultrasonic devices

Environmental options for handling waste by-products are also addressed. If you are considering changing your cleaning methods, this webinar is for you.

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.

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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).

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EASA’s Stator Core Test Form provides a step-by-step procedure for calculating the number of turns and cable size required for a loop test. The form also has provision for recording the meter and temperature readings obtained during the test. Core sketches that show the location of measured dimensions and a wiring diagram of instrument connections are also included.

For more details on stator core testing, see Section 7 of the EASA Technical Manual.

Chuck Yung 
EASA Technical Support Specialist 

Due to economies of scale, the use of cast iron is a popular choice in the manufacturing of NEMA and IEC frames. Cast iron is robust and easily machined. It is dimensionally stable and transfers heat well. However, foundry work is an energy-intense process, not well-suited to limited production runs. 

For larger electric motors, which are manufactured in smaller quanti­ties, the frame is more often fabri­cated from steel. You may have heard various nicknames for this type of construction: “shoe-box,” “skeleton frame,” “bathtubs” or other terms. Those who work on these motors regularly know that the frame requires care in handling, especially those fit­ted with sleeve bearings.