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Product Abstract

Electric Motor Predictive and Preventive Maintenance Guide

Product ID:NP-7502
Date Published:02-May-1992
Sector Name:Nuclear
Document Type:Technical Results
Price:No Charge

This Product is publicly available

   1.62 MB - Adobe PDF (.pdf)

Electric motor failure could result in lost capacity as well as excessive repair and maintenance costs. This guide provides information on establishing an effective maintenance program to help prevent unexpected motor failures, costly downtime, and unnecessary maintenance costs. Specifically, the guide summarizes technical data relative to four basic power plant motor types and associated components.


Maintenance recommendations proposed by electric motor vendors have sometimes encouraged many overly conservative maintenance practices. These practices have led to excessive maintenance activities and costs that have not provided an extra margin of operability. Current work was prompted by a need to determine appropriate maintenance techniques and tasks for specific applications based on the type and size of electric motors and components.


To provide utilities with guidance for establishing an effective motor maintenance program, which should prevent unexpected failures through planned motor maintenance efforts.


EPRI relied on supply and repair facility personnel as well as the Nuclear Plant Reliability Data System to evaluate the operational history and failure modes of various motor types and sizes. They reviewed numerous electrical test and inspection methods, determining how effectively each method revealed the operating condition of electric motors. Then they compiled these methods and matched them with appropriate motor types based on their use in performing motor evaluations. The analysis evaluated motor components as well as the entire motor unit to detect signals that could provide trending information.


This guide summarizes technical data on the four basic types of power plant motors and their components; it correlates failure causes, symptoms, and modes. The guide further addresses the significant causes of motor failures and outlines methods to optimize service life and minimize maintenance costs through appropriate preventive maintenance programs. Test and maintenance recommendations for different motor sizes and types are arranged to allow clear comparison of motor reliability with function and cost effectiveness. Throughout the guide, easy-to-read charts and tables chronicle the data.

On the basis of information provided in this guide, maintenance personnel in nuclear and fossil plants can customize their programs for specific motors according to service applications and operating conditions. To assist in this effort, the guide includes a glossary of terms, regreasing guidelines for motors with antifriction bearings, and oil-monitoring guidelines for electric motors with oil bath bearings.

EPRI Perspective

This guide provides a foundation for an effective electric motor maintenance program with simple, but viable, testing routines that increase assurance of efficient motor operation. In all, the guide simplifies selection of predictive and preventive maintenance tasks to help maintenance personnel plan motor repairs during scheduled outages and avoid costly unexpected failures. Related EPRI reports include GS-7352, Manual of Bearing Failure and Repair; NP-3357, Condition Monitoring of Nuclear Plant Electrical Equipment; and CS-5328, Signature Analysis, Rotating Equipment Monitoring.

Program 41.05.01   Nuclear Maintenance Application Center (NMAC)
  • Maintenance
  • Induction Motors
  • Electric Motors
  • Electrical Equipment
  • Bearings

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