Ingeniero

An Analytical Approach to Solving Motor Vibration Problems
Copyright material IEEE
Paper No. PCIC-99-XX
William R. Finley
Senior Member
Industrial Products Division
Siemens Energy & Automation, Inc.
4620 Forest Ave.
Norwood, OH 45212

Mark M. Hodowanec
Member
Industrial Products Division
Siemens Energy & Automation, Inc.
4620 Forest Ave.
Norwood, OH 45212

Abstract: Vibrationproblems in induction motors can be
extremely frustrating and may lead to greatly reduced
reliability. It is imperative, in all operations and manufacturing
processes that down time is avoided or minimized. If a
problem does occur the source of the problem is quickly
identified and corrected.
With proper knowledge and
diagnostic procedures, it is normally possible to quickly
pinpoint thecause of the vibration. All too often erroneous
conclusions are reached as a consequence of not
understanding the root cause o f the vibration. This may result
in trying to fix an incorrectly diagnosed problem, spending a
significant amount of time and money in the process. By
utilizing the proper data collection and analysis techniques,
the true source of the vibration can be discovered. Thisincludes, but is not limited to:
Electrical imbalance
Mechanical unbalance – motor, coupling, or driven equipment
Mechanical effects – looseness, rubbing, bearings, etc.
External effects - base, driven equipment, misalignment, etc.
Resonance, critical speeds, reed critical etc.
Once the electrical and mechanical interactions in a motor are
understood, and the influence external componentshave on
the apparent motor vibration, identification of the offending
component is usually straightforward. This paper provides an
analytical approach for expeditiously understanding and
solving these types of problems.

I.

Warren G. Holter
Industrial Products Division
Siemens Energy & Automation, Inc.
4620 Forest Ave.
Norwood, OH 45212

differentiate between cause and effect. Forthis to happen,
one must first understand the root cause of the vibration. In
other words: where does the force come from? Is the
vibratory force the cause of the high levels of vibration or is
there a resonance that amplifies the vibratory response.
Perhaps the support structure is just not stiff enough to
minimize the displacement. In this paper the various sources
of electrical andmechanical forces will be explained.
Additionally, how the motor reacts or transmits this force and
how this force can be amplified or minimized will be explained
as well. When a vibration problem occurs it is important that
one use a good systematic, analytical approach in resolving
the problem. This includes performing the proper diagnostic
tests. The process starts by listing all the possiblecauses for
the particular identified frequency of vibration and any
variations under different operating conditions. Then eliminate
the incorrect causes one by one until all that remains is the
true source of the problem, and now this can be efficiently
eliminated.
II.

SOURCES OF VIBRATION

There are many electrical and mechanical forces present in
induction motors that can causevibrations. A
dditionally,
interaction of these various forces make identification of the
root cause elusive. In subsequent sections, the major
mechanisms are discussed. For a more comprehensive list of
electrically and mechanically induced vibrations Table I should
be referenced.

INTRODUCTION

Much has been written about vibration over the years. This
includes many papers and books onvibration in general and a
number of papers on vibration in induction motors in
particular. This is an ongoing subject, continually extended by
advances in analytical and diagnostic tools and methods. For
this reason, and because this is an important and complex
subject, it is worthwhile periodically to both present any new
knowledge and experience as well as to review prior
knowledge and...