Diagnostics of Induction Motor with Broken Bars
Using Motor Current Signature Analysis (MCSA)
Lin Liu, Suri
Ganeriwala
SpectraQuest Inc., 8201 Hermitage Road, Richmond, VA 23228
Published: January 2006
Abstract
Using a Machinery Fault SimulatorTM
(MFS) machine, we studied the diagnostics of the common types of
fault in induction motors by motor current signature analysis (MCSA)
as well as vibration analysis. The faults studied include both
electrical and mechanical defects. Specifically, they are broken
rotor bar, shorted stator wiring, and motor bearing defect. This is
the first of a series of our tech notes on the topic of motor
diagnostics.
Full Text (PDF)
Introduction
The test is performed on a Machinery Fault SimulatorTM
(MFS) made by SpectraQuest.
In this study, we have two rotors with different
numbers of broken bars. One rotor has three bars broke, and the
other one has six bars broke.
Three motors are tested and they are: a good
motor, the motor with three broken bars, and the motor with six
broken bars. During the test, the power supply line frequency is
fixed at 35 Hz by the motor controller. A tachometer detects the
rotor speed and the speed is recorded for each test. From the line
frequency and the rotor speed data, the per unit slip data can be
obtained.
Fig 1: Current Spectrum for Rotor with Three Rotor
Bars Broken
Fig 2: Effect of Load on Amplitude Decrease
between Twice Slip Sideband and Line Component
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