PAGE 22 — GENERATOR SERVICE AND TROUBLESHOOTING MANUAL — REV. #0 (08/29/23)
When generators, welders and electric motors are new
the insulation should be at its highest level of resistance.
During equipment use, insulation is subject to many effects
which can cause it to fail.
These causes can be mechanical damage, vibrations,
excessive heat or cold, dirt, oil, corrosive vapors, and even
moisture from humidity. During the life of a conductor’s
insulation all of these causes are at work in combination
with electrical stresses. If a pinhole or a crack develops in
the insulation (Figure 15), moisture and foreign matter can
penetrate the surfaces of the insulation.
Figure 15. Insulation Leak
This provides for a low-resistance path for leakage current.
Once the insulation has begun to deteriorate all elements
of causes tend to combine until excessive current leakage
is allowed through the insulation.
At times the drop in insulation resistance can be sudden,
such as occurs if the equipment is ooded. Normally
insulation resistance drops gradually and gives plenty of
warning if checked as preventative maintenance.
CONDUCTOR
INSULATION
VOLTAGE
(E)
LEAK
RESIST
(R)
CURRENT
(I)
PIN HOLE/
CRACK
ELECTRICAL INSPECTION
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