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.

This book was developed to help electric motor technicians and engineers prevent repeated failures because the root cause of failure was never determined. By using a proven methodology combined with extensive lists of known causes of failures, one can identify the actual cause of failure without being an “industry expert.” In fact, when properly used, this material will polish one’s diagnostic skills that would qualify one as an industry expert.

Revised September 2022!
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Occasionally an end user wants to take a motor designed for horizontal mounting and use it in a vertical position. In this article, we will address some of the key mechanical factors that should be considered when applying a horizontal ball bearing motor in a vertical mounting position.

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.

EASA’s Stator Core Test Form provides a step-by-step procedure for calculating the number of turns and cable size required for a loop test.

The International Electrotechnical Commission (IEC) standard 60529, “Degrees of protection provided by enclosures (IP code),” addresses the degrees of protection for electrical machines (motors and generators). The “IP” acronym means “international protection” but is sometimes referred to as “ingress protection.” The IP code is commonly displayed on the nameplates of metric machines that are manufactured to IEC standards.

La placa de datos de un motor eléctrico revela mucha información valiosa acerca de la capacidad y desempeño de la máquina.

The nameplate of an electric motor reveals much valuable information about the capability and performance of the machine.

Fundamental to every good mechanical repair is the ability to disassemble, repair and reassemble the motor correctly without unnecessary damage to any of the motor parts. This sounds simple, and yet too many costly mistakes are made in this process of taking things apart. If every motor repaired was in “as new” condition, the task would be much simpler. This manual introduces much of the basics to electric motor disassembly and assembly.