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IR
Thermography in Predictive Maintenance

Fig.
1 |
Infrared
inspections have proven their value over the past
30 years when performed on electrical distribution
equipment, as part of a comprehensive predictive
maintenance program. The image to the left (Fig.
1) quickly and clearly reveals the isolated-resistance-rise
(IRR) caused by a poor connection on Phase A of
this single-phase, fused disconnect.
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In
combination with conventional vibration analysis,
infrared imaging of moving parts, such as in the
motor-coupling-compressor assembly to the right
(Fig. 2), greatly enhances the maintenance testing
of mechanical equipment. The infrared image identifies
a progressing failure mode arising from deteriorated
bearings on the motor. In this case a follow-up
vibration test may be performed to aid in analysis
of the problem.
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Fig.
2
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Fig.
3
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What's
wrong with this picture?(Fig.3) The hot spot does
not seem to be originating from the energised
conductors. Instead, the highest temperatures
are seen on the cabinet adjacent to the bushing
and a gradient is formed outward from that area.
In this situation a ferrous bushing was used on
this cabinet at the egress point of a 3 phase
meter cabinet. Normally, this would not pose an
inductive problem as all 3 phase conductors are
exiting the same opening and the 120 degree current
phase angle difference between them would cause
their individual magnetic fields to cancel each
other out. However, the infrared image shows clearly
that the 3-phase loads are not balanced and some
magnetic coupling is taking place, inducing a
voltage that is responsible for eddy-currents
within the cabinet. The resulting temperature
rise betrays their existence to the infrared camera.
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GlencoMetrics
Inc.
16 Sims Cres., Unit # 28, Richmond Hill, Ontario, Canada,
L4B 2P1
Tel: (905) 764-9297, Fax: (905) 764-8084
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