PROPER ELECTRICAL SAFETY TESTING TAKES SHOCK OUT OF WORKPLACE

Calculating Motor Load With A Voltmeter and Ammeter 

Electrical Motor Diagnostics: WIIFM: What’s In It For Me?
By Howard Penrose PhD, CMRP

Impulse Testing as a Predictive Maintenance Tool by E. Wiedenbrug SM IEEE, G. Frey M IEEE, J. Wilson, M IEEE,

Electrical Motor Diagnostics Business Case Development by Howard Penrose Ph.D. and Carol Vesier Ph.D.

Low Voltage Vs High Voltage Testing
by Dr. Howard W. Penrose, Ph.D.

Since the mid-1980’s, new technologies have been introduced that perform low voltage nondestructive evaluation of your electrical rotating machinery. Prior to this introduction, high voltage test method manufacturers would commonly caution users about the potential destructive tendencies of their technologies.

After this period, the story changed as the low voltage technologies took market share. The result? Marketing became the driving force with engineering the victim.

It is the purpose of this paper to discuss some of the myth and misdirection presented, and to reaffirm the direction of the industry. For de-energized Motor Circuit Analysis (MCA), the capabilities include: Cable faults; Winding shorts; Insulation to ground faults; and, Rotor/Air gap issues.

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Online Condition Monitoring of Motors Using Electrical Signal Analysis
by Aditya Korde B.E. Diagnostic Technologies India Pvt. Ltd.

Motor current acts as an excellent transducer for detecting faults in the motor.  Spectrum analysis of the motor's current and voltage signals can detect various faults without disturbing its operation.  Typical faults that are detectable include:

• Rotor bar damage

• Misalignment/unbalance

• Foundation Looseness

• Static eccentricity

• Dynamic eccentricity

• Core damage

• Loose wedges

• Interturn shorts

• Defective bearing

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Identifying the Motor Rotor Bar Related Peaks in a Spectrum
By Alan Friedman, DLI Engineering Corp

The motor bar peak in a spectrum appears at a frequency equal to the number of motor bars multiplied by the shaft rate of the machine. Although initially, most analysts will have no idea how many motor bars there are, identifying the peak that relates to the motor bars is fairly simple to accomplish. The reason for this is that the motor bar peak will have peaks on either side of it, spaced 120 Hz away (100 Hz where electrical line frequency is 50Hz). These peaks are termed “sidebands” and they are caused by the modulation of the motor rotor by the electromagnetic forces that cause the motor to spin.

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US Department of Energy Releases MotorMaster + Version 4.0

MotorMaster+ (MM+) is an electric motor energy and management tool that is provided at no charge by the US Department of Energy.  It supports motor management functions for virtually any sized facility and has also been designed for utility auditors, industrial energy coordinators, and plant or consulting engineers.  MM+ supports motor and motor system improvement planning by identifying the most efficient action for a given repair or motor purchase decision.

More...Click here to read about MotorMaster + Version 4.0 (23k pdf)

Basic Electrical Troubleshooting
By Pete Bechard, PdMA Corporation

A boiler feed pump being powered by two 3500 HP induction motors appears to be developing a problem. Failure of this pump will result in the loss of a generator currently producing half of the station’s power output. Operators are complaining that a large compressor on several occasions has failed to start. A controller just doesn’t sound the way it used to. A cooling fan has developed an audible “beat” sound during operation. One of the most enjoyable aspects of working as an electrician is taking such compelling evidence as “appears to be developing a problem,” determining what is actually going on, and making a sound decision on the correct course of action. Successfully troubleshooting a complex piece of equipment gives a technician a tremendous sense of satisfaction. Having an effective troubleshooting plan and following it can help obtain this feeling of satisfaction.

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Electric Motor Energy and Reliability Analysis Using the US Department of Energy’s MotorMaster+ by Howard W. Penrose, Ph.D, Jim Hanna, Johnny Douglass, Chris Cockrill, Greg Lee, Dave Van Horn

Energy efficiency in electric motor systems presents significant opportunities within industry. In a US Department of Energy report provided by Xenergy1, "In 1994, electric motor-driven systems used in industrial processes consumed 679 billion kWh – 23 percent of all electricity sold in the United States…. Implementation of all well established motor system energy efficiency measures and practices that meet reasonable investment criteria will yield annual energy savings of 75 to 122 billion kWh, with a value of $3.6 to $5.8 billion…" Reliability and maintenance practices on electric motor systems also provide an excellent opportunity for both energy efficiency and production cost avoidance2, "Drivepower users and utilities have made significant investments in recent years to improve the efficiency of motor-driven systems. The longevity of these measures – as well as the amount of energy they save – depends heavily on the quality of the maintenance they receive. Although it is usual to think of motor system maintenance as an activity that follows other drivepower decisions, it is actually the first step for most facilities in moving towards more efficient motor systems…The efficiencies of mechanical equipment, in general, can be increased typically 10 to 15 percent by proper maintenance."

More...Click here to read Electric Motor Energy and Reliability Analysis Using the US Department of Energy’s MotorMaster+ (239k pdf)

Variable Frequency Drive Motor Testing
by Noah Bethel, PdMA Corporation

VFD Technology has changed the way most of us do business in one way or another.  If you have not been influenced in some way by this new technology, then stand by, your time is coming.  We have all heard the horror stories about motor failures occurring minutes or hours after applying a new drive, or seen the advertisements pushing us to demand the new inverter duty wiring to prevent these drive related motor failures.  What should you know and whom should you ask to get your answers? 

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Test Methods for Determining the Impact of Motor Condition on Motor Efficiency and Reliability
by Dr Howard W. Penrose, Ph.D.

This article discusses the financial impact of motor condition on electric motor efficiency and reliability by reviewing a combination of Motor Circuit Analysis (MCA) and vibration techniques. Cost impacts on energy, production and maintenance will be outlined. The primary areas of concern are phase balance, rotor bars, cleanliness and bearing issues.

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Identifying Motor Defects Through Fault Zone Analysis
by Noah Bethel of PdMA

ELECTRICAL maintenance personnel have for years been limited to troubleshooting with no more than a fluke and a Megger.  This unfortunately does not provide enough information to allow most electricians to feel totally confident in determining if an electrical problem exists or not.  A mechanical operator once said, “If a problem exists with a piece of equipment, and there is an electric cable within ten feet of it, then it must be an electrical problem!”  If you are involved with electric maintenance you have probably heard at some time in your career, “It must be the motor.”  If you are into mechanical maintenance you have likely heard, “It’s probably the pump.  Let’s uncouple it.” 

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Click here to read Electric Motor Monitoring and Diagnostic System (463k pdf)

MOTORLINK CASE HISTORIES ABOARD SHIP   (480VAC TO 6600 VAC) “Vacuum Pump”

MotorLink was installed on a 120,000 DWT tanker in late 2001.  During system testing for the Baseline Status Report MotorLink identified a problem with the Main Vacuum Pump. 

This is not a serious fault but it appears that it had actually been present over a three-year period.  This piece of equipment had been cited in the thermographic report each year since 1999.  Each year one of the engineers would clean and tighten the connections indicated in the infrared picture and would think that the problem was repaired.  The next year, the same fault would again be indicated by the thermography report.  When MotorLink was being installed the engineer advised that this item had just been repaired.

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