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Articles in Industry Publications

Crooked Teeth? We’ve Got Braces!

How Using Clamps When Pulling Magnet Wire Helps Prevent Splayed Teeth

  • January 2024
  • Number of views: 848
Article

Unless great care is taken, pulling magnet wire from a motor stator often bends or splays the lamination’s end teeth. Bent teeth, or teeth that have been splayed outward at the ends of the core stack, will likely compromise the quality of the repair job. Therefore, we have designed and implemented the use of disc clamps to hold the stator tooth tips in place while pulling magnet wire from the slots. The clamping fixtures described in the photos have helped ensure that we avoid damaging the stator teeth during the stripping process.

¿Dientes Torcidos? ¡Tenemos Ortodoncia!

Cómo el usar discos de retención al tirar del alambre magneto previene doblar los dientes de las laminaciones

  • January 2024
  • Number of views: 467
Article

A no ser que se tenga mucho cuidado, tirar del alambre magneto al desmantelar el estator de un motor a menudo deforma o dobla los dientes de las laminaciones. Estos dientes deformados comprometerán la calidad de la reparación y hay estudios que demuestran que este problema puede reducir la eficiencia del motor. Sin embargo, aunque esta reducción puede ser pequeña, genera altos costos y desperdicio de energía.

How to Measure Magnet Wire

  • March 2023
  • Number of views: 2406
Video

This video shows one step in collecting motor winding data: how to measure magnet wire.

Why “White Coils” are a “Red Flag”

The importance of preventing the ingress of air during global vacuum pressure impregnation of form-coil windings

  • September 2022
  • Number of views: 2503
Article

The goal of vacuum pressure impregnation is complete saturation of a winding with insulating resin. As resin penetrates the insulating materials, it causes them to darken. If some insulation is a lighter shade, the coil or jumper is not fully saturated. The winding is not properly protected, and if the problem is not addressed, it is likely to cause premature failure of the unit. This could result in costly warranty work, or at a minimum, will be a failure to provide your customers with the quality they expect and deserve.

Porqué las "Bobinas Bancas" son una "Señal de Alarma"

La importancia de prevenir el ingreso de aire durante la impregnación global por vacío y presión de los bobinados preformados

  • September 2022
  • Number of views: 1808
Article

El objetivo de la impregnación por vacío y presión (VPI) es saturar completamente un devanado con resina aislante. A medida que la resina penetra en los materiales aislantes, los oscurece y al drenar la resina VPI del devanado, todo el aislamiento de las cabezas queda oscuro en un tono uniforme. El aislamiento de la conexión también debe quedar oscuro de forma pareja. Si algún aislamiento muestra un tono más claro, la bobina o el puente no han quedado completamente saturados y el devanado no está debidamente protegido. Si no se soluciona el problema, es probable que esto provoque un fallo prematuro en el equipo. Esto podría generar una garantía costosa o, como mínimo, la reparación no brindará a sus clientes la calidad que esperan y merecen.

Best AC Rewind Practices

  • February 2021
  • Number of views: 15029
FREE for Members of EASA
Webinar recording

This webinar recording shares some of the “best practice” rewind methods used by (and learned from) EASA service centers around the world: connection recognition, best insulating materials, wire choices and tips to save time and effort.

AC Stator Form Coil Data Sheet

  • February 2021
  • Number of views: 7419
Form/Worksheet

This handy form provides fields to record all of the details needed to document and/or order replacement coils for an AC form-wound machine. The form also includes detailed descriptions/definitions of the data to be recorded in each field. 

Controlling Stator Copper Losses in Formed Coil Rewinds

  • May 2020
  • Number of views: 10520
FREE for Members of EASA
Webinar recording

This webinar recording looks at several aspects of winding design to prevent increased temperature rise and decreased efficiency.

Considerations for random to form winding conversions

  • December 2019
  • Number of views: 10439
Article

With a steady increase in random wound AC motor sizes and the obvious superiority of the form coil winding, one area where we can help improve customers' motor reliability is by redesigning those large random wound motors to accept form coils. Most repairers would agree that machines rated larger than 600 hp (450 kW) should be designed as form coil machines. Likewise, those rated over 2 kV will be much more reliable as form coil machines.

No one wants to rewind a motor using 60 #14 AWG (62- 1.6 mm) wires in hand. With an abundance of niche suppliers of stator laminations, the cost and practicality of converting a random wound motor to form coil are available to nearly all service centers. Replacement laminations can be punched, laser-cut or water-cut, and supplied with very reasonable delivery times.

Consideraciones para convertir bobinados de alambre redondo a pletina (solera)

  • December 2019
  • Number of views: 8917
Article

Con el aumento continuo de los tamaños de los motores CA y la obvia superioridad de los devanados con bobinas preformadas (pletina o solera), un área en la que podemos ayudar a mejorar la confiabilidad de los motores de nuestros clientes es rediseñando estos motores grandes de alambre redondo para que acepten bobinas preformadas. La mayoría de los reparadores estarían de acuerdo en que las máquinas de alambre redondo por arriba de 600 hp (450 kW) deberían rediseñarse con bobinas preformadas. Así mismo, aquellas con tensiones nominales superiores a 2 kV serían más confiables con bobinas de pletina.

Nadie quiere rebobinar un motor con 60 #14 AWG (62- 1.6 mm). Con la abundancia de proveedores especializados en laminaciones de estatores, el costo y la practicidad para convertir motores de alambre redondo a pletina está al alcance de casi todos los centros de servicio. Las laminaciones para reemplazar el núcleo pueden ser troqueladas o cortadas con láser o agua y entregadas en tiempos muy razonables.

Magnetic Wedges

  • February 2019
  • Number of views: 13632
Webinar recording

An increasing number of manufacturers are using magnetic wedges in their form-wound machines. When a winder fails to replace magnetic wedges in kind, the winding temperature rise can increase by 20°C, and the magnetizing current can increase by 20% or more.

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Induction Motor Rotor Windings: Squirrel-Cage and Wound Rotor Basics for the Technician

  • January 2018
  • Number of views: 10693
Webinar recording

This presentation covers induction motor basics for squirrel-cage and wound rotor motors

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Stator Core Testing: Know What You Have Before You Wind It

  • April 2017
  • Number of views: 5877
Webinar recording

This presentation covers:

  • The importance of the stator core test 
  • Simple theory to share with technicians and customers 
  • Practical approach for testing small stators demonstrated 
  • Eliminating pen + paper; loop test calculations for any device 
  • Assessing the results
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Common recommendations for stored motors

  • September 2013
  • Number of views: 10120
Article

When an electric motor is expected to be stored for an appreciable time before it is placed into service, certain steps should be taken to ensure that it will be suitable for operation when it is needed. The practical limitation we need to recognize is that much of what we do when putting a motor into long-term storage has to be undone when the same motor is moved into operation. This article addresses common recommendations for stored motors.

Benefits of the AC hi-pot for new form coil stator windings

  • August 2013
  • Number of views: 6973
Article

The October 2012 Currents article titled "How to properly test AC stator and wound rotor windings" provides a thorough explanation on the proper application of insulation resistance, winding resistance, surge testing and high potential testing for stators and wound rotors. The article emphasizes that NEMA MG 1-2011 specifies AC and DC high potential (hi-pot) test levels for new windings and does not recommend repeated application of the high potential test. This is reinforced in EASA's Recommended Practice for the Repair of Rotating Electrical Apparatus (ANSI/EASA AR100-2010) which calls for reduced voltage levels for repeated tests should they be required. This article is intended to provide additional information on the high potential test performed on new windings. Specifically, it addresses the advantages of AC high potential testing for new, form coil stator windings. Topics discussed include: A real-world example Destructive test? Sizing the AC test set Example calculation Bibliographic references to additional reference materials

Cold stripping procedures for form coil machines

  • April 2009
  • Number of views: 4804
Article

There are times when a winding cannot be processed through the burnout oven, so it must be removed "cold." The bond strength of most resins is approximately 8-10 psi (55-70 kPa), which means that a fairly large coil might have nearly 3,000 pounds (1350 kg) of bonding force with the slot. In those cases, there are some useful tips that can be used to reduce the difficulty in removing the coils. Many of the techniques in this article can be adapted for open-slot, wound rotors and armatures.

Form coil rewind tips for motors 6 kV and above

  • February 2006
  • Number of views: 6251
Article

When rewinding motors rated 6 kV and above, there are certain steps beyond the normal rewind procedures used for 2.3 kV/4 kV machines. Whether a machine is to be VPI processed makes a difference in how the winding should be treated.

Brick and terrace designs: Two variations of form-wound coils

  • July 2001
  • Number of views: 5163
Article

It is very important to take accurate data when you rewind a form-wound motor or generator, especially if the coils will be made by an outside coil manufacturer. There are a couple of variations to the standard coil design that are not common, but that you may come across from time to time.

Training Film 8: Winding Stators With Formed Coils

  • June 1984
  • Number of views: 3426
Video

Describes the procedures for inserting a formed coil into a stator. Shows proper tools and various wedging methods. Includes connecting the coils and insulating the connections.

Training Film 7, Part 2: Manufacturing Form Coils (Insulating Form Coils)

  • June 1984
  • Number of views: 3663
Video

Teaches how to determine type of connection, number of parallel circuits, turns per coil, wire size, span and groups. Shows step-by-step way to properly record all information.

Training Film 7, Part 1: Manufacturing Form Coils (Loop Winding and Coil Forming)

  • June 1984
  • Number of views: 3646
Video

Shows how to determine loop dimensions, winding the loop, insulating it and spreading the coils, along with determining the dimensions of the spread coil.