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Auxiliary cooling of electric motors (and other equipment)

  • January 2017
  • Number of views: 643
  • Article rating: No rating
Article

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 work-ing 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.

Refrigeración auxiliar de motores eléctricos (y otros equipos)

  • January 2017
  • Number of views: 642
  • Article rating: No rating
Article

Keeping it cool: A look at causes of motor overheating

  • March 2015
  • Number of views: 834
  • Article rating: No rating
Article

We know that excessive temperature and moisture are the largest contributors to bearing and winding failures. Understanding the source of the increased temperature will help us to correct the problem and improve the machine’s life expectancy.

Safe starting of motors: Pay attention to temperature increase

  • May 2014
  • Number of views: 532
  • Article rating: No rating
Article

The most stressful time for electric motors is during starting. At starting, the motor current is the highest it will ever be. This is referred to as starting or locked rotor current. These different terms describe that when the shaft speed is zero, the current is maximum. Once the motor has been successfully started, the load current level is reached and the cooling circuit of the motor is able to dissipate the additional heat produced by the starting current. Restarting the motor before this additional heat has been dissipated means more heat in the form of kW•h will be added on top of that which is there. Each subsequent start before the additional heat has been dissipated will add more heat — raising the temperature until some component in the motor reaches its failure point. This article looks at safe starting practices for electric motors.

Thermistors: What they are and how they work

  • March 2014
  • Number of views: 511
  • Article rating: No rating
Article

Thermistors, derived from the term thermally sensitive resistors, are a very accurate and cost effective method for measuring temperature. Thermistors are usually two-terminal semiconductor devices made from semi-conductor materials that have an electrical resistance that varies non-linearly with temperature. Some materials provide better stability while others have higher resistance ranges and are fabricated into smaller thermistors. Each specificthermistor has its own unique resistance versus temperature characteristic. 

Cool facts about cooling electric motors

Whether old or new design, lowering temperatures based on same principles

  • July 2011
  • Number of views: 550
  • Article rating: No rating
Article

Whether an old or new design, lowering temperatures is based on the same principles. 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.

When it comes to motors, how hot is hot?

Temperatures that are too high affect machine performance, life

  • June 2011
  • Number of views: 362
  • Article rating: No rating
Article

We often hear from members that a customer has reported that a motor that has been repaired is now running hot. We always ask how hot and the reply frequently is: "Well, I can't hold my hand on it!" Let's think about that answer for a minute. The typical human can tolerate about 60-65°C (140-150°F) depending on calluses, threshold of pain, how many people are watching, etc. ... Temperature is often the Number 1 enemy of the electric motor. Care must be taken in the design, application and maintenance of these machines to optimize their performance and life. All that said, it is unsafe to lay your hand on a motor to see if it is too hot; get a thermometer instead.

Cuando se trata de motores ¿Qué tan caliente es caliente?

Las temperaturas muy altas afectan la vida útil del motor

  • June 2011
  • Number of views: 445
  • Article rating: No rating
Article

Frecuentemente escuchamos decir a nuestros miembros, que uno de sus clientes le ha informado que un motor que había sido reparado, ahora se calienta. Nosotros siempre les preguntamos ¿Qué tan caliente? y por lo general responden “Bueno, no puedo mantener mi mano sobre él”.

Vamos a pensar un minuto en esta respuesta. La mano del ser humano típico, puede soportar una temperatura entre 60-65°C (140-150°F), dependi-endo de las callosidades, el dolor que pueda tolerar, cuantas personas estén observando, etc. ... la temperatura es el enemigo número 1 de los motores eléctricos. Para optimizar la vida útil y el buen funcionamiento de los motores, se debe tener cuidado con el diseño, la aplicación y el mantenimiento de estas máquinas. Teniendo en cuenta todo lo anterior, no se considera seguro tocar con la mano la superfcie de un motor para saber si está muy caliente. En vez de esto, lo mejor es utilizar un termómetro.

Taming those misbehaving motors: Troubleshooting tips for some of the most common problems

  • December 2009
  • Number of views: 392
  • Article rating: No rating
Article

Three of the most common motor problem calls received from members by EASA's Technical Support Department are:

  • "The motor is drawing high no-load current."
  • "The current of the three line leads is not balanced."
  • "The motor is running hot."

If you have ever faced one or more of these issues, and it's almost certain you have, read on.

What does it mean when a rewound motor runs "hot"? Items to check to make sure it's operating properly

  • July 2008
  • Number of views: 353
  • Article rating: No rating
Article

Has this ever happened to you? You have rewound a motor without changing the design at all; you tested the motor before you sent it out, and everything appeared to be fine. But now your customer wants you to figure out what is wrong, or rewind the motor again. Before you consider this, there are a few things to check to see if the motor is, in fact, running properly. It is quite possible that the motor ran "hot" before it failed, but what are the chances that someone on-site put their hand to the frame before it had to be rewound?

Getting The Most From Your Electric Motors

Getting The Most From Your Electric Motors - coverThis 40-page booklet provides a great marketing tool for your service center! Use it to provide end users with information that will help them obtain the longest, most efficient and cost-effective operation from general and definite purpose electric motors.

This booklet covers topics such as:

  • Installation, startup and baseline information
  • Operational monitoring and maintenance
  • Motor and baseline installation data
  • How to read a motor nameplate
  • Motor storage recommendations

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EASA Technical Manual

EASA Technical Manual cover

The EASA Technical Manual is the association's definitive and most complete publication. It's available FREE to members in an online format. Members can also download PDFs of the entire manual or individual sections.

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ANSI/EASA AR100-2015

ANSI/EASA AR100-2015 cover

Recommended Practice for the Repair of Rotating Electrical Apparatus
This is a must-have guide to the repair of rotating electrical machines. Its purpose is to establish recommended practices in each step of the rotating electrical apparatus rewinding and rebuilding processes.

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EASA AR200

EASA AR200: Guide for the Repair of Power and Distribution Transformers cover

Guide for the Repair of Power and Distribution Transformers
This document establishes guidelines for each step of the repair of power transformers, describing record keeping, tests, analysis, and general guidelines for the repair of power transformers.

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