Articles: Motor and Power System Testing

A Better Understanding of Rotor Dynamics and Support Stiffness

More Data Provides More Answers

by Ron Brook

A Closer Look at Air Gap Eccentricity

by Douglas E. Swinskey & Peter M. Bechard

The first step in evaluating test data is understanding the relationship to the circuit's Fault Zones and how abnormalities in a specific Fault Zone affect the performance of the motor. The six Fault Zones (Power Quality, Power Circuit, Stator, Insulation, Rotor, and Air Gap) are derived from the most common electrically related motor failures in industrial environments. The Air Gap Fault Zone describes the measurable distance between the rotor and stator within the motor. Air gap eccentricity is a condition that occurs when a non-uniformity in the air gap between the rotor and stator exists.

 

A Cradle to Grave Approach - Motor Management at Its Best

by Noah Bethel, CMRP

Ask a motor manufacturer how long one of its motors is expected to live, and the response will be something like, "20-plus years in the right environment." Ask the same question in a facility that uses such a motor and the answer is more likely to be, "If we get five years out of it, we'll be happy!" Why does this discrepancy exist? Why do motors die of an infant mortality instead of living to the ripe old age for which they are designed and built? The answer has to do with the failure to optimize motor management and maintenance.

 

Adventures in Engineering Standards - Behind the Scenes of Creating IEEE Std 43-2000

by Howard W. Penrose, PhD, CMRP

Engineering can be a boring career with everyone working with known measurements and absolutes. There is never any doubt that the information contained in a standard or textbook is fact because everything is static, mathematical, and measurable. At least, that is what most people tend to think.

Defects in Nonceramic Insulators: Can They be Detected in a Timely Manner?

by S. Gorur and S. Sivasubramaniyam Department of Electrical Engineering, Arizona State University, Tempe, AZ, USA

This work was performed under a PSERC (Power Systems Engineering Research Center) funded project at Arizona State University

This paper is a continuation of the work reported during the Daycor users meeting. The electric field measurement method has been explored to determine its potential for timely detection of defects in nonceramic insulators. Various types of defects were simulated and the external electric field was computed. It is shown that the electric field method used presently is not sensitive enough to permit early detection of defective. There is a need for an improved method, perhaps periodic corona inspection could be the answer.

 

Diagnosing Rotor Bar Issues with Torque and Current Signature Analysis

by Drew Norman

Over the years rotor bar problems have been a diagnostic challenge for motor maintenance professionals.  Now with current signature, spectral torque analysis and automated computer diagnostic software, defining rotor health problems has been made fairly simple.  However, problems arise when professionals do not understand the underlying principles of the what’s, whys and how’s of dynamic rotor testing.

Evaluating Winding Connections With Infrared

Introduction

An area that is often overlooked in the rewinding of an electric motor are the internal connections of the winding. Most coils have multiple wires making up one ‘conductor' (Figure 1). The reason for this is to allow the wire to be more flexible for installation while allowing enough cross section for the amount of current that the conductor must carry. This generates a situation where improper brazing, crimping or other methods of making the connections will generate a hot-spot due to IR losses.

Maintaining The Long Term Reliability of Critical Power Systems in Water Processing Plants

By Reza Tajali
Schneider Electric

The critical applications in water and wastewater processing plants require uninterruptible power of a high quality. The most basic of these systems utilize automatic throw-over switches. The most advanced systems include UPS (Uninterruptible Power Supply) and generator equipment that maintain the continuity of power without one cycle of interruption.

Managing the Complete Motor System

Modern management practices often do not take into account the importance of motor systems maintenance and management requirements. Through efforts in cost control, many industrial and commercial firms reduce maintenance staffs, take least cost approaches to corrective actions and sacrifice preventive maintenance programs.

Motor Current Analysis (MCA) Test Results Can be Misleading if Drive Train Load Isn’t Considered

By: Jason Bolte, CMRP, Allied Reliability, Inc.

A constant issue when applying Condition Monitoring technologies is buy-in that the technology is capable of detection of failure modes in machinery. It is as critical to ensure that readings are interpreted properly to determine that a fault does not exist as much as that one does. Nothing sabotages buy-in more than the knowledge that repair activity has taken place that was unnecessary. One of the keys to effective data analysis is that we take consistent repeatable data. This is particularly of note when considering motor loading when performing Motor Current Signature Analysis (MCSA) testing.

Motor Management Programs and an Auto Industry Success Story

by Howard W Penrose, Ph.D., CMRP and Robert Varcoe

A variety of concepts related to the term ‘motor management’ have been presented within industry since the 1990s.  Many of these programs are actually ‘energy-efficient electric motor retrofit or repair versus replace’ ideas which make up only a small portion of the overall opportunities when properly managing electric motor systems.

PdM of Mechanical Failures Using Electrical Measurements for Instantaneous Torque

by Ernesto J. Wiedenburg

Electric dynamic predictive maintenance is a field of continual rapid technology development. The same theoretical background, which made the first torque controlled VFDs possible, is now utilized to monitor the shaft torque by measuring only the stator currents and voltages. The first diagnostic use of the instantaneous torque signal as part of an off-the-shelf solution for field maintenance reached the market in 1999. In the last ten years, it has shown a dramatic increase in the quality of the information obtained over previously used techniques.

 

Proper Electrical Safety Testing Takes Shock Out of Workplace

by The Seaward Group

The safety of everyday electrical devices is widely taken for granted. All too often though, the lax approach to proper electrical safety testing can result in tragedy. For example, back in 2005 a woman suffered a fatal electrical shock in a restaurant washroom in England after using the hand dryer. It was subsequently determined that the dryer was faulty, a preventable situation that should have been detected by the eatery's employees.

Take the Big Picture Approach

Managing the Complete Motor System

Modern management practices often do not take into account the importance of motor systems maintenance and management requirements. Through efforts in cost control, many industrial and commercial firms reduce maintenance staffs, take least cost approaches to corrective actions and sacrifice preventive maintenance programs. The result has been increased energy costs and downtime resulting from equipment not operating to full potential and failing unexpectedly. The problem results in $100's of billions of dollars in additional energy consumption and lost revenue. Unfortunately, in many cases, the connection between the cause and effect is not made.

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