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. This article addresses some of the key mechanical factors that should be considered when applying a horizontal ball-bearing motor in a vertical mounting 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

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

Determining the source of noise in an electric motor is often more challenging than correcting it. A methodical investigative approach, however, can narrow the possibilities and make it easier to resolve the issue—with one caveat. If the noise is due to something in the motor design (e.g., a manufacturing defect or anomaly), a solution may be impossible or impractical. With that in mind, let’s review the primary sources of noise in electric motors—magnetic, mechanical, and windage—as well as their causes and ways to reduce or eliminate them.

Areas examined in this article include:

• Magnetic noise
  • Slip noise
  • Skewing
  • Unequal air gap
• Mechanical noise
  • Loose stator core
  • Bearings
  • Airborne noise
• Windage noise

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

The Electrical Apparatus Service Association (EASA) has published two documents to help users and service providers ensure that motor repairs performed reflect good practices that maintain or improve a machine's energy efficiency and reliability: ANSI/EASA Standard AR100-2015: Recommended Practice for the Repair of Rotating Electrical Apparatus and the "Good Practice Guide" of the 2003 study The Effect of Repair/Rewinding on Motor Efficiency, by EASA and the Association of Electrical and Mechanical Trades (AEMT). These documents serve as tools by which service centers and end users can speak the same language when it comes to level-setting service and performance expectations on motor repair and rewind.

Also, a little more than a year ago, EASA launched its electric motor repair accreditation program, based on AR100 and the "Good Practice Guide." The program benefits both end-users and service providers by ensuring that electric motor repairs conform to the good practices identified in the aforementioned documents."

Electric motor efficiency can be maintained during repair and rewind by following defined good practices. This article builds on my previous discussion of PM and PdM for three-phase squirrel-cage motors ("PM and PdM for electric motors") by outlining some of the expectations and good practices for repairs of these types of motors.

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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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By Mike Howell
EASA Technical Support Specialist

Right-sizing of three-phase induction motors for different applications – and striking a balance between reliability and efficiency – isn’t always easy, but it can be cost-effective. Before the days of comprehensive predictive and preventive maintenance programs, the conventional approach to reliability was conservatism, both in design and in application. That’s to say that on a 25 hp application, you’d find a very conservatively designed 60 hp motor that was really 75 hp “under the hood.” And yes, the motor would last a very long time, but it would have an inflated (and often ignored) operational cost. Many of these robustly engineered applications are still out there, and it can be well worth the effort to identify and correct them.

Some of the topics covered include:

• New vs existing applications
• Determining the actual load
• Determining typical loading by measuring the average input power
• Line amps
• Locked-rotor amps
• Starting torque
• Special applications

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We often hear the terms preventive maintenance (PM) and predictive maintenance (PdM) of electric motors, but far less often do we give consideration to the tasks associated with these methods of maintaining motor operation and extending operating service life. This article addresses some of the more common activities associated with PM and PdM, with the focus on three-phase squirrel cage motors.

Preventive maintenance:

• Insulation resistance (IR) test
• Polarization index (PI) test
• Motor current signature analysis (MCSA)
• Mechanical activities such as lubrication, lubricant level checks, and lubricant analysis
• Visual inspection
• Thermal scanning
• Ultrasonic testing
• Cleaning
• Belt tensioning
• Bolt tightness checks

Predictive maintenance activities:

• Trending and assessing most activities associated with preventive maintenance
• Vibration analysis
• Checking and adjusting alignment

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Matthew Conville, MBA, PE
EASA Technical Support Specialist

Balancing plant maintenance costs and activities with the need to achieve production goals is a daily challenge for most maintenance professionals. Since the motor-driven system is often a critical component in this dynamic, let’s look at some best practices to help it achieve those goals and meet customer demands.

To plant maintenance pros in most industries, these are familiar questions:

• “How do we improve reliability within our plant?”
• “How can we reduce unplanned downtime, so our production stays more consistent?”
• “How can we decrease our total cost of ownership of our equipment?”

They phrase it differently, but ultimately each of these questions is about improving the efficiency and reliability of the motor-driven system. Although that encompasses a wide range of components including fans, pumps, and drives, here we’ll focus on the electric motors.

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

The most frequent concern about high current with a three-phase motor is high no-load current. But the broad issue of high no-load current isn’t the only three-phase motor issue to which plants should pay heed: High current with load and lower-than-expected no-load current are potential areas of concern, too. This article published in Plant Services explores the sources of all of these.

• High no-load current: Motor not rewound
• Motor with no nameplate
• High no-load current: Rewound motor
• High current with load

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

Those familiar with industrial electric motors have heard “DC is dead” for decades as advances in variable-frequency drive (VFD) technology for AC squirrel cage induction motors (SCIMs) seemed destined to replace their DC counterparts in every conceivable application.

But just as DC’s demise was greatly exaggerated, so too is the prospect of successor technologies replacing the installed base of SCIMs any time soon – whether for new applications or replacement motors. Still, it’s wise to recognize that change is coming, and that two of the newer technologies are already in common use – permanent magnet motors and reluctance motors.

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