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Webinar Recordings

Controlling Stator Copper Losses in Formed Coil Rewinds

  • May 2020
  • Number of views: 1279
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: 1000
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: 904
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: 561
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.

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

  • January 2018
  • Number of views: 794
Webinar recording

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

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

  • April 2017
  • Number of views: 560
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

Common recommendations for stored motors

  • September 2013
  • Number of views: 656
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: 852
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: 629
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: 870
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.