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This article provides an update to a paper presented in 2006, sharing the results of a decade of core repair. The process described is for a microconversion coreplate of electrical steel laminations used in ac stators, ac rotors, and dc armatures. The treatment process restores the coreplate and avoids the laborious restack process, saving time and reducing the cost to the end user.

IEEE standard 1068-2015 for repair and rewinding electric motors has had several modifications made to the 2009 edition to make it more useful to users of electric machines. Along with general revisions, sections have been added to cover the repair of synchronous machine rotors of all types, magnetic slot wedges, permanent magnet rotor machines, bearing currents on adjustable-speed drive (ASD)-driven motors, rehabilitating flooded motors, and a repair checklist. As before, the standard was developed by people associated with motor repairs for many years and is intended for users in the petroleum, chemical process. and other industries.

This paper provides an update to the paper presented in 2006, sharing the results of a decade of core repair. The process described is for a micro-conversion coreplate of electrical steel laminations used in AC stators, AC rotors and DC armatures. The treatment process restores coreplate and avoids the laborious restack process, saving time and reducing cost to the end user.

This paper provides the user of AC electric motors a guide in selecting an electric motor service center and, for those who have made this selection, it provides useful material in performing periodic audits.

In the context of rotating electrical machines, air gap is the physical separation between the rotor and stator core. The role of air gap is not as simple as first appears. Air gap design has evolved beyond uncomplicated mechanical distance into the consideration of a combination of various physical restrictions, electrical factors, and performance criteria. Various complex interdependent relationships and practical constraints are presented and evaluated.

The evolution of electric motor design as it pertains to cooling methods provides insights about better ways to cool machines in service. The array of methods engineers have devised to solve the same problems are fascinating yet reassuring because many things remain unchanged even after a century of progress. This article discusses how motors are cooled and how heat dissipation can be improved for applications that fall outside the normal operating conditions defined by the National Electrical Manufacturers Association (NEMA) Standard MG 1 [1].

IEEE Std 1068-2015 for repair and rewinding electric motors has several modifications to the 2009 edition to make it more useful to users of electric machines. As well as general revisions, sections have been added to cover: Repair of synchronous machine rotors of all types; magnetic slot wedges; permanent magnet rotor machines; bearing currents on ASD driven motors; rehabilitating flooded motors and a Repair Checklist. As before, the standard was developed by people who have been associated with motor repairs for many years and is intended for users in the petroleum, chemical process and other industries. As well as specifying technical requirements, it describes what should be done before a machine fails (e.g. evaluating shops and plant record keeping), what to specify when a failure occurs, in situ motor record-keeping, failure analysis, monitoring progress, and post repair functions. Many users already use the standard as the basis of their own corporate standard. Using it should result in higher quality, cost effective and timely repairs.

With literally hundreds of electric motor manufacturers from which to choose, sorting through options to find the best value can be a daunting task. This paper draws on the author's forty-plus years of experience to share practical methods for comparing motors before purchase. Interwoven into the paper are suggestions and techniques for improving designs of motors already in service. Areas of interest include electrical windings, bearings, rotor designs, ventilation and balancing.

This Article Details the Updates and modifications to the 1996 revision of IEEE 1068, Recommended Practice for the Repair and Rewinding of Motors in the Petroleum and Chemical Industry. It contains only selected topics present within the standard and should not be treated as a substitute for the entire standard. A major change in the document is its evolution to full standard status. The IEEE Standards Association also granted the working group's petition to broaden the scope and title to include process industries in general. Such recognition acknowledges its value to those employing machines in demanding services and severe environments, such as the cement trade and pulp and paper processing. IEEE Standard 1068?2010 was restructured to better track the methodologies and processes employed in present-day repair facilities. Substantive improvements include incorporation of currently available technology, document specific testing, evaluation criteria, and clarification of end user and service center responsibilities.

This Article Discusses the Basic components of core loss (hysteresis and eddy-current losses), the effect of frequency and lamination thickness, and other contributing factors. It also explains the effect of operating frequency of squirrel cage type-rotors and armatures and provides correction factors.

Although there is a great deal of emphasis on replacement of National Electrical Manufacturers Association (NEMA) frame motors with EPAct/premium efficient motors, the vast majority of medium-voltage motors in use today fall outside the scope of EPAct. Many of these machines offer considerable opportunities to enhance performance during future rewinds. There are several ways to improve the reliability and efficiency of existing form-wound motors. Some of these opportunities can be capitalized on during the course of a repair, by optimizing the winding design, with little additional effort beyond the routine rewind. Others can be applied to in-service machines with no requirement to remove the machine from service. This study evaluated 94 sets of form coil winding data, comparing wire and slot dimensions, to assess the opportunity for magnet wire slot fill improvement. Motor ratings ranged from 200 to 5,000 hp (149 to 3730 kW), from 2 to 32 poles, 2.3 to 13.2 kV. The preponderance of data (43 motors) was for two- and four-pole machines, since those are most common in the petrochemical industry.

For the end user of electric motors, it is important to maximize repair quality at minimum cost. At the same time, most recognize the truth in the old adage “you get what you pay for.” Coordination of the expectations of the end user and service center is important to ensure that the end user gets the level of quality desired without paying too much for unnecessary features. The amount of testing and documentation required by the motor end user varies widely by industry. Additional testing takes time, and time is money. This article offers guidelines to assist the end user in selecting and working with the service center. Equipment needed to perform a quality repair is described, with suggestions for evaluating service centers as potential vendors. Numerous so-called decision models are used by industry to direct the decision process when a motor fails. Most are simple and do not consider the reality of downtime costs or manufacturing timetables. A portion of this article presents a more realisti...

Pulp and paper production facilities are often concentrated along coastal regions or rivers, and therefore are especially vulnerable to hurricanes, typhoons or floods. Electric motors, switchgear and related equipment are sensitive to damage from flooding, and replacements often have long lead times. This paper offers practical methods for restoring electrical equipment, as well as guidance for the repair-replace decisions with an eye towards getting the plant back in operation as soon as possible. It also offers advice about expected life reduction for electrical equipment that is not properly handled after such an event. Because similar production facilities are regionally concentrated, multiple facilities impacted by the same disaster will be competing for limited repair and replacement resources. Having a proactive recovery plan before the storm can significantly reduce the time required to restore production. Understanding the long-term effects of water (especially saltwater) on electric motors and generators is vital to capital expense forecasting for the years following a major storm.

The offline single-phase rotor rotation test is frequently used in the field for assessing the integrity of the rotor cage without motor disassembly. However, the inconvenience of the large variable voltage supply requirement has triggered the advent of a portable low-voltage version of the test also known as the rotor influence check. This test has recently become common in the pulp and paper industry as it is convenient to use in an industrial environment. However, concerns on the reliability of the test have been raised due to frequent false test indications. The objective of this work is to provide an analysis and experimental evaluation of low-voltage rotor tests under controlled rotor fault conditions on 380-V and 6.6-kV motors. The results of the low-voltage test reveal that it cannot provide reliable diagnosis due to the low excitation flux level, particularly for motors with the closed rotor slot design. The single-phase rotation test and online current spectrum analysis are also performed under identical fault conditions to show that the fault conditions can be detected with standard tests.

The evolution of electric motor design, as it pertains to cooling methods, provides insights about better ways to cool machines in service. The array of methods engineers have devised to solve the same problems is fascinating yet reassuring, because many things remain unchanged even after a century of progress. This paper discusses how motors are cooled and how heat dissipation can be improved for applications that fall outside the “normal operating conditions” defined by NEMA Stds. MG 1-2011 [1].

Countless times each year, lightning is wrongly blamed for electric motor failures. This paper addresses ways to differentiate between damage from lightning and that caused by inadequate ground fault protection or multiple start attempts after the initial failure. Transient conditions, rapid bus transfer, and ungrounded systems often mislead the repairer into blaming lightning for motor failures. A list of similar transients would have to include re-closure, improperly located power factor correction (PFC) capacitors, accidental connection of a new dual-voltage motor for the wrong voltage, and lightning.

Benchmarking of electric motors can reveal deterioration of the motor's performance characteristics, allowing the opportunity to schedule corrective action, thus minimizing unscheduled downtime and repair costs. In the event of a failure, benchmarking records can offer clues as to the root cause of the failure. The benchmarking process should be on-going throughout the life of the motor. It should ideally start with the manufacturer's tests under controlled conditions and then be part of the installation, operation, maintenance and repair of the motor. The degree and extent of benchmarking should be based on cost to bench mark, cost to repair, cost of lost production, and consequences of a premature failure.

The loop test described in IEEE 432 has long been used to evaluate the condition of stator cores before rewinding. The acceptance of this test is largely due to the rigorous peer-review process underlying all IEEE Standards. Originally developed to test stator cores, the loop test is increasingly used to perform testing of other types of electrical cores, such as: squirrel cage induction motor rotors, wound rotor cores and DC armatures. These results are often misinterpreted due to a general lack of understanding of the principles behind the test. This paper discusses the basic components of core loss (hysteresis and eddy-current losses), the effect of frequency and lamination thickness, and other contributing factors. It also explains the operating frequency of squirrel cage type rotors and armatures, and provides correction factors.

This paper details the updates and modifications to the 1996 revision of IEEE 1068 Recommended Practice for the Repair and Rewinding of Motors in the Petroleum and Chemical Industry. A major change in the document is its evolution to full standard status, noted in the title of this paper. The IEEE Standards Association also granted the Working Group's petition to broaden the scope and title to include process industries in general. Such recognition acknowledges its value to those employing machines in demanding services and severe environments, such as the cement trade and pulp & paper processing. IEEE 1068 was restructured to better track the methodologies and processes employed in present day repair facilities. Substantive improvements include incorporation of currently available technology, document specific testing, evaluation criteria, and clarification of end-user and service center responsibilities.

Several good papers have been written on the motor repair or replace decision process. Because plant total cost of ownership and reliability are the ultimate goals, the field of motor management has become a popular subject often discussed more than implemented. The intent of this paper is to discuss how the value of total motor management is related to the motor repair or replace decision, and some suggestions on how to get started on evaluating the decision. The plant maintenance process consists not only of planning, but often reacting to maintenance needs. The reaction often overshadows the planning as the urgency of a breakdown takes priority over prevention. Making the correct repair/replace decision can be the key to long-term reliability in the process. While sometimes difficult to implement, motor planning is essential to plant reliability. This paper will show how the motor management process supports the repair vs. replace decision process.

This paper describes the changes to IEEE 1068 Standard for the Repair and Rewinding of Electric Motors in the Petroleum and Chemical Industry. Last revised in 1996 as a Recommended Practice, one of the changes during this revision cycle was to upgrade IEEE 1068 to a standard. In February 2007, the IEEE Standards Association accepted a change in the project request to broaden the scope and title to include "other" process industries. This action recognizes the value of the subject and enables direct use of the document by associated severe environment and demanding service industries such as pulp and paper. The document has been reorganized to follow the logical flow-through of a representative motor repair. Numerous updates with respect to available technology have been made. The new standard clarifies the responsibilities of both the end-user and service center.