This manual covers horizontal and vertical squirrel-cage induction motors in the 300 to 5,000 horsepower range, low- and medium-voltage. Most of the principles covered apply to other sizes as well. This manual focuses primarily on IEC motors and standards.

There are many misconceptions about Service Factor (SF) in the industry. Some feel it is meant for temporary excursions into overload conditions; others consider it to be an allowance for permanent overload. The truth is that it is neither. 

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.

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.

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.

This presentation shows a methodical approach and techniques for tackling this difficult balancing problem.

This presentation provides an overview of ambient, winding temperature rise, and winding temperature, and addresses detectors for measuring winding temperature, namely thermostats, resistance temperature detectors (RTDs), thermocouples and thermistors.

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.