MAINTENANCE Page 19
Table 2 – Check Points for Periodic Inspection (cont.)
Check
Point
Check Item Check Method Criteria What to do
Main Circuit Dust on
surface of
vacuum
interrupter
Visual inspection. Make sure there is no
dust on the surface.
Wipe with a clean,
dry cloth.
Insulation
Frame and
Flanges
Dust, foreign
matter or
damage
Visual inspection. Make sure there is no
dust, foreign matter or
breakage.
Wipe with a clean,
dry cloth. If
damaged, contact
Toshiba.
Control
Circuits
Auxiliary
Switch
See Table 3. Contact wear and wipe.
Make sure there is no
dust.
Replace if wear or
damage is
excessive. See
Table 1 for
tightening torque
specifications
Drive unit Visual inspection. Check for overheating
and discoloration.
Replace if damaged.
Wiring Visual inspection.
Tighten using a
screwdriver.
Check for discoloration
and tightness.
Repair if
disconnected.
Tighten if loose.
See Table 1 for
tightening torque
specifications.
Insulation
Resistance
Measure-
ment
Resistance
from main
circuit to
ground
Measure insulation
resistance between
phases, between
electrodes, and
between circuits and
ground. Megger test
at 1000V.
Resistance should be
50MΩ or greater.
Resistance
from control
circuits to
ground
Measure insulation
resistance between
circuits and ground.
Megger test at
500V.
Resistance should be
1MΩ or greater.
If the insulation
resistance is low,
wipe off the vacuum
interrupter and other
insulation surfaces
with a clean dry
cloth and then
repeat the test. If
necessary, replace
faulty parts.