Chuck Yung
EASA Senior Technical Support Specialist

Although the earliest practical DC motor was built by Moritz Jacobi in 1834, it was over the next 40 years that men like Thomas Davenport, Emil Stohrer and George Westinghouse brought DC machines into industrial use.

It’s inspiring to realize that working DC motors have been around for over 160 years. For the past century, DC machines over 30 or 40 kW have been cooled in the same manner – by mounting a squirrel cage blower directly over the commutator.

By Jim Bryan
EASA Technical Support Specialist (retired)

The effects of excessive temperature on motor performance are notorious. After moisture, they are the greatest contributor to bearing and winding failures. Understanding the source of increased temperature is key to correcting the problem and improving the reliability of your facility’s motor fleet.

Topics in this article cover:

• Overload and service factor
• Ventilation
• Voltage variation
• Electrical steel
• Current density
• Circulating currents
• Harmonics

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By Chuck Yung
EASA Senior Tecnical Support Specialist

The evolution of electric motor design as it pertains to cooling methods provides insights about better ways to cool machines in service. The array of methods engineers have devised to solve the same problems are fascinating yet reassuring because many things remain unchanged even after a century of progress. This article discusses how motors are cooled and how heat dissipation can be improved for applications that fall outside the normal operating conditions defined by the National Electrical Manufacturers Association (NEMA) Standard MG 1.

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Chuck Yung
EASA Senior Technical Support Specialist

I’ve often commented on how for­tunate we are to work on such a variety of electric motor designs. One day, you are working on a new design some designer has recently created, and the next day you are repairing a motor that could be in a museum. It’s fascinating to see the different ways engineers have devised to do the same thing, and yet reassuring to see how many things remain unchanged even after a century of electric motors. 

One aspect of electric motors that could be placed in both categories is the way an electric motor is cooled. This article takes a look at how motors are cooled and how we can improve cool­ing for some of the special applications we encounter.

Chuck Yung 
EASA Technical Support Specialist 

Most of us involved in the repair of electrical equipment have a good understanding of how an electric motor works–especially the stator and ro­tor. But the fan can appear deceptively simple. Fans are pretty interesting, once we learn a few “affinity laws”—rules that also apply to blowers and impellers. This article will review some basic facts about fans that explain how small changes to a fan can make a BIG difference in the following critical areas: 

• Volume of air moved
• Static pressure
• Load
• Losses (efficiency)

These rules hold true for fan applications, im­pellers in pumping applications, and cooling fans on electric motors. When applied to the external fan of a TEFC (IP-54) motor, these rules offer some real opportunities for efficiency improvement. 

Often an overhung fan is balanced in a single plane, only to find that the vibration has shifted to the outboard bearing. Attempts to use standard two-plane techniques may result in calculated correction weights that are very large and produce poor results. There are more effective ways to approach this common problem. This presentation shows a methodical approach and techniques for tackling this difficult balancing problem.

Target audience: This presentation is intended for field service balancing technicians, supervisors and managers.

Chuck Yung
Especialista Sénior de Soporte Técnico de EASA

Aunque el primer motor de C.C. práctico fue construido por Moritz Jacobi en 1834, fue durante los 40 años siguientes que hombres como Thomas Davenport, Emil Stohrer y George Westinghouse fabricaron máquinas de C.C. para uso industrial.

Es inspirador darse cuenta que los motores de C.C. han estado trabajando por más de 160 años. Durante el siglo pasado, las máquinas de C.C. con potencias por arriba de los treinta o cuarenta kW han sido refrigeradas de la misma forma, montando un soplador de aire de jaula de ardilla directamente en el colector.