23.
INSPECTION AND MAIN'TEMNCE
23.3
Replacing
Pam
The inverter consists of a number of electronic component
parts
such
as
semiconductor
devices.
Due
to their
physical
properties,
it
is anticipated that the following component
patts
will deteriorate
with time,
kadw
to troubles or hered performance of the inverter. They should
be
rephced
at regular Intervals for preventive maintenance.
(1)
Cooling fan
A cooling fan is used to cool heat generating parts such as semiconductor devices in the
main circuit. Although the service life
of
the bearing used in the cooling fan is, under normal
operating conditions,
20,000
hours, it will vary in the range of
10,OOO
to
35,000
hours
depending on ambient temperatures.
Therefore, if the system
is
continuously operated, it is necessary to replace the cooling fan
assembly every
two
to three years. Beside this regular replacement, if abnormal noise or
vibration is detecled during inspection, the cooling fan assembly should
be
replaced imme-
diately.
A
large capacity aluminum electrolytic capacitor for smoothing the current is
used
in me direct
current circuit
in
the main circuit.
The
performance of the capacitor
is
degraded due to the
influence of ripple, etc. Although the service life
of
the capacitor varies depending on the am-
bient temperatures and operating conditions, the capacitor should be replaced every five
years assuming that the parameter unit is used within specified environmental limits.
Since the deterioration of a capacitor accelerates over lime, it should be checked at least
once a year. As it approaches the end of service life, it should be checked every six months
or at shorter intenals. The inspection items and defects which require the capacitor to be
replaced are summarized below.
1)
Case conditions: Expansion
of
the case at the side and bottom
2)
Sealing conditions: Excessive curvature or cracks
3)
Safety valve conditions: Excessive expansion
of
the valve or an actuated valve
4)
Others:
(2)
Smoothing
wpncltor
Check for cracks, discoloration, leakage, or other defects. Measure the capacity.
If
measured capacity is less than
85%
of rated, the capacitor should
be
replaced.
(3)
Relays
Relay contacts deteriorate with use. Relays should be replaced according to the total number
of
makebreak operations (service life).
The following table shows the part replacement intervals. In addition to the parts given in this
table, lamps and other component parts having shorter service life should be inspected at
regular intervals.
(4)
Replacemsnt
criterb
I
Part
name
I
Typlcal
nplllcrment
Intervals
[
Ropl-t
proodur
Cooling
Ian
Smoothing
capacitor
2
to
3
years
-
RelaV5
Replace
on
evidence
of
deterioration
5
years
-99-
.
..
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