Document Type:Technical Results
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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.
BackgroundMaintenance 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.
ObjectiveTo provide utilities with guidance for establishing an effective motor
maintenance program, which should prevent unexpected failures through
planned motor maintenance efforts.
ApproachEPRI 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
ResultsThis 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 PerspectiveThis 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.
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