Jerry Lipski
Jerry Lipski, LLC
Scheerville, IN

Ever run across brush arcing or vexing commutation issues? This paper, presented at the 2013 EASA Convention, covers:

• Definition of commutation
• Basic magnetism
• Commutation and AC in a DC armature core
• Brush construction
• The basic commutator and placement of carbon brushes
• Carbon brush arcing; what are the brushes telling you? + field case studies
• Sanding brushes
• Most common surface conditions
• Field experiences with drives
• Brushholders
• Slip ring application
• Field settings (neutral, tape method)
• Field/service center testing

Chuck Yung
EASA Senior Technical Support Specialist

Although the rotating equipment repair industry has been around for over a century, technology continues to introduce new test instruments and procedures. Some of these are good: surge test, growler, core loss test; some are bad: core testing a rotor at 60 times its operating frequency, or performing a Hipot at several times the prescribed value; and some are just plain ugly.

This paper will help you to sort out which are which, and help educate your customers as to the reasons why. Standards organizations (IEEE, ANSI, IEC) have developed specific tests, with much scientific thought as to how stringent a test should be. ANSI/EASA AR100: Recommended Practice for the Repair of Rotating Electrical Apparatus consistently references the relevant standard(s) for each test.

This paper, presented at the 2013 EASA Convention, summarizes the accepted and other electrical tests required by motor and generator end users. It covers:

• Various standards (IEEE, IEC, NEMA, ANSI and API) that describe and legitimize most of the tests used by our industry
• Other tests, not supported by any recognized standards, that end users request repairers to perform
• An outline of these tests, with supporting standards, which should be useful when discussing testing requirements with end users

Vicki Warren, Iris Power
Mississauga, Ontario
Brian F. Moore, Georgia Power
Atlanta, Georgia

Surveys have shown that stator winding insulation failure account for about 40% of motor failures in motors rated 2300V and above. In addition, the work force in general is losing its technical experience. This impacts both the customers we serve and our own internal work force that fixes the equipment.  Lastly, there seems to be a shift toward a more political type customer base that is less likely to own up to their contribution to motor failures. These reasons combine to force motor shops into better testing to know that a more reliable product is being shipped.

Several old and new test methods have recently gained popularity with AC induction motor maintenance specialists.  This paper, presented at the 2013 EASA Convention, will examine Power Factor Tip-up and Partial discharge testing to assess stator winding conditions for motors rated 2300V and above. Both tests will be evaluated for: effectiveness; which windings/types of machines the test is effective; set-up; interpretation and limitations.

Topics discussed include:

• Brief review of stator winding failure mechanisms
• Brief review of power factor and power factor tip-up
  • The theory/math behind it
  • Georgia Power’s use as a sorting tool
• Partial discharge terms that apply to power factor and tip-up testing
  •   Inception and extinction voltage
  •   Magnitude
  •   Polarity
• Reading actual power factor and test data sheets
  •   Advantages and limitations of off-line tests
  •   Deciding if there is a problem or not
• Case studies: What to do next (if you suspect a problem)
  • Partial discharge testing (brief theory and expected results)
  • Dynamometer testing or full-load testing at the customer’s plant us

Mike Howell
EASA Technical Support Specialist

Most service centers do not routinely rewind stators in the voltage range of 11-13.8 kV (13.8 kV will be used throughout the discussion for simplicity). These machines represent a small percentage of machines repaired and typically present significant financial exposure in the event of an in-process or warranty related failure. Organizational efforts to enter this product line should be carefully planned to minimize risk to the service center and to assure customer requirements are met.

This paper, presented at the 2013 EASA Convention, presents a generic product quality planning process for industrial motor stator windings rated 13.8 kV. Emphasis is placed on analyzing gaps between a 4 kV rewind and a 13.8 kV rewind as they relate to stator winding design, insulation system validation and process control. The process analysis model considers materials, equipment, people, environment and methods.

Machines rated in the 6 kV class are excluded from the discussion with exception to a short explanation near the end of the paper providing rationale for the exclusion.

• Stator winding design
• Insulation system validation
• Process control

The process analysis model will consider materials, equipment, people, environment and methods.

Rick Hoadley
ABB

Whenever an application engineer is planning on installing adjustable speed drives for AC motors, line current harmonics and reflected waves are two factors that need to be addressed. Four basic questions should be answered in order to successfully commission the drive system:

1. What is my power system like today
2. What impact will the additional drives have on the power quality for the other equipment
3. If needed, what harmonics mitigation method should be used
4. How long and what type of cable is used between the drive and motor

This paper, presented at the 2013 EASA Convention, deals with understanding IEEE Std 519 and various mitigation methods in order to meet those recommendations. It also reviews the types of filtering that is available to reduce the reflected waves seen at the motor terminals.

Topics covered include:

• Overview of drives topologies
• The differences between 6,12,18 pulse and active front end drives
• How the differences in drives relate to harmonics generated
• Filters on either end of the drive to mitigate the effects of harmonics, as well as voltage spikes and other potential damaging effects on the motor

Ron Widup
Shermco Industries
Irving, TX

Learn from an industry veteran about safety topics you may think you know but that can cost your firm substantially if you’re not diligent.

• Fall protection
• Fork lift hazards and relevant regulations
• Material handling/lifting
• Cranes and hoists
• Machine shop hazards
• Cautions regarding abrasive blasting
• Painting irritants

Gene Vogel
EASA Pump & Vibration Specialist

Increasingly, it is not enough to just “fix” that pump. Customers want and need to understand the “why” behind the failure. This pump failure case study looks at:

• Failure methodology and how it was used
• The possible causes of failure
• The final analysis
• How the analysis impacted the repair approach

Ron Widup
Shermco Industries, Inc.

This paper, presented at the 2013 EASA Convention, provides an overview of NFPA 70E.

The hazard of electrical shock has been known since the first electrical devices were designed in the 1800s. Arc flash and arc blast have also been recognized, but due to the inability to quantify these two hazards, there was nothing that could be done to effectively protect the worker from them.

That began to change in 1996, when the first arc testing took place. As the industry was then able to determine the hazard created by an electrical arc flash, protective equipment was designed to provide that protection, and NFPA 70E (in the 2000 edition) provided the first generally available guide to choosing PPE to protect workers from the arc flash hazard. 

Advancements have been made, both in our understanding of the arc flash hazard, as well as how to design more effective PPE and clothing that provides a higher level of protection and is more comfortable to wear. This includes lighter weight arc flash clothing and arc-rated windows and face shields that have better light transmission through them. These two factors increase the acceptance by workers of the provided arc-rated PPE and clothing and has increased their usage. 

Topics covered in this paper include:

• The latest changes and the reasoning behind them
• Important wording changes concerning energized work
• How to implement the changes
• Personal protective equipment requirements
• How to avoid costly mistakes that could put your employees and company at risk

Charles LeMone
LeMone Technical Services
Roanoke, VA 

Is the induction motor the preferred answer in industrial drive applications? What is happening to the synchronous, DC and wound rotor motor (WRM) in those applications? This paper discusses:

• Observations as customers replace synchronous, WRM and DC machines with the induction motor
• Why synchronous motors are used in industrial applications
• Issues with WRM and soft starters
• A case study of a 12,000 hp 4-pole synchronous motor and a soft starter
• What needs to be done to modernize the older synchronous motor starter?
• How a brushless synchronous motor operates
• Brushless synchronous motor protection

Gene Vogel
EASA Pump & Vibration Specialist

Vibration has three primary parameters; amplitude, frequency and phase. Previous presentations and papers have focused on the two most common parameters, amplitude and frequency. These two are the primary tools for determining if a machine vibration is a problem, and what the cause of the vibration might be. This paper, presented at the 2013 EASA Convention, focuses on the third parameter: phase angle.

While vibration phase angle has several perspectives, this paper focuses on the most straightforward aspect — the angular relationship between vibratory motions of two different locations on a machine. Inherently, then, phase angle is based on two different inputs and measuring phase requires two input signals. The two signals can be two vibration transducers, or a single vibration transducer and a reference pulse signal from a photo tach, laser tach, key phasor or such. For those who are familiar with using a strobe light and a single transducer to measure phase angle, your eye and the reference mark on the shaft provide the second input.

Phase angle is seldom used to detect when a problem occurs on a machine. But it is a powerful tool for diagnosing vibration in many common situations. It also provides necessary data for dynamic balancing. For phase to be useful in any situation, it must be coupled with the corresponding vibration amplitude. Together, phase and amplitude constitute a vector. A basic understanding of vectors is fundamental to vibration analysis.

This paper covers:

• Amplitude and phase concepts
• Shaft alignment vector analysis
• Planar shape sketches
• Animated Operating Deflection Shape (ODS)
• ODS instrumentation and software

Vibration data from field measurements can tell a great deal about the health of machine components and required follow-up action. Beyond acquired time waveform or spectral frequency pattern data, several tools are available in most portable vibration instruments to determine natural frequencies, shaft centerline motion, and the relative movement of machine components. Drawing on practical examples, this paper will also cover:

• Startup/coast down analysis
• Bump tests
• Cross-channel phase measurement
• Demodulation techniques
• Orbital plots

Gene Vogel
EASA Pump & Vibration Specialist

The ability to measure machinery vibration is essential to machinery repair. But vibration is a complex phenomenon, with multiple parameters; specifically, amplitude, frequency and phase. So unlike temperature, pressure or other single parameter indicators, to use vibration as an effective machine condition indicator, technicians need more than simple meter and 5 minutes of instruction. The most common vibration related task for EASA service centers is acceptance testing for repaired machines. Even this basic task requires:

• Knowledge of vibration fundamentals
• Adequate vibration instrumentation
• Documented acceptance criteria
• Proper mounting methods
• An awareness of advance analysis techniques

This paper addresses the concerns related to insuring the service center has adequate vibration instrumentation. While needs vary among service centers, the basic instrument required is a portable vibration analyzer. In order to qualify as a vibration analyzer, the most basic instrument functions are the ability to measure vibration amplitude and frequency, and common tools for analyzing a vibration spectrum. There are a number of instruments that meet these basic requirements, and most offer additional useful capabilities. Choosing an instrument that meets a specific service center’s needs should involve all of the stakeholders, which includes owners, managers, engineers and technicians. For smaller service centers, it may be one person who wears all those hats, and the decision process is simplified. For larger service centers, input from a dozen people may be needed, and there will be trade-offs on costs vs. benefits. In either case, and those in between, it’s important that considerations include:

• Features and capabilities
• Cost
• Convenience
• Durability
• Support
• Training

This paper focuses on features and capabilities. Not to diminish the importance of the other components, but those are best left to discussion between the service center and the various instrument vendors.

This paper covers:

• Heritage instruments
• Spectrum analyzers
• Balancing instruments
• Online monitors
• Portable vibration level meters
• Proximity probes and instruments
• Accelerometer transducers

Chuck Yung
EASA Senior Technical Support Specialist

Even though they comprise a small portion of electric motors in service, wound rotor motors are disproportionately represented in EASA’s tech support call volume. There are several misconceptions about how they work. This paper will describe how they are applied and explain several simple but critical tests for the repairer.

• What are the rotor leads used for?
• What is the purpose of the steps/resistance changes?
• How should you evaluate the completed repair?
• Common causes of failure and how to prove them to your customer
• Considerations and cautions for retrofitting a wound rotor motor with a VFD
• Identifying wave wound rotor connections