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Maintenance
2. The second step in the removal procedure is to de-ener-
gize control power to the circuit breaker. Open the con-
trol power disconnect device.
3. Rack the breaker to the "DISCONNECT" position.
4. Perform the spring discharge check. This is done by first
pressing the red Trip pushbutton. Second, press the black
Close pushbutton. Third, press the red Trip pushbutton
again, and observe the spring condition indicator. It
should read Discharge (Refer to Circuit Breaker Operator
/ Manual SGIM-9918 (3AH) or SGIM-3398 (3AF)).
5. Remove the circuit breaker from the switchgear. Refer
to the preceding installation section of this manual for
special instructions and precautions regarding removal
of a circuit breaker which is not at floor level.
Checks of the Primary Power Path
The primary power path consists of the three vacuum
interrupters, the three upper and the three lower primary
disconnects. These components are checked for cleanliness
and condition (Figure 7). The vacuum interrupters are
discussed in the Circuit Breaker Operator Manual SGIM-
9918 (3AH) or SGIM-3398 (3AF).
Note: Maximum Contact Resistance is read from pri-
mary bus stab to primary bus stab with primary dis-
connects removed. A value of 13 micro-ohms should
be added to the maximum contact resistance speci-
fied in Circuit Breaker Operator Manual SGIM-9918
(3AH) or SGIM-3398 (3AF).
Cleanliness Check
Figure 7 is a side view of the Circuit Breaker with the insu-
lating barriers removed to show the vacuum interrupter,
and the upper and lower primary disconnects.
All of these components must be clean and free of dirt or
foreign objects. Use a dry lint-free cloth. For stubborn
dirt, use a clean cloth saturated with denatured alcohol (ex-
cept for the vacuum interrupters). For stubborn dirt on a
vacuum interrupter use a damp cloth and then thoroughly
dry using a dry lint-free cloth.
The phase barriers are plates of glass polyester insulating
material and attached to the circuit breaker to provide suit-
able electrical insulation between the vacuum interrupter
primary circuits and the switchgear.
Always re-install the phase barriers carefully to the original
location prior to inserting the circuit breaker into the
switchgear.
Primary Disconnects
Reference Figure 7.
When the contacts are mated with the switchgear's primary
stud assembly, there is forceful contact distributed over a
wide area. This maintains low current flow per individual
contact finger.
Figure 7. Primary Power Path
Inspect the contact fingers for any evidence of burning or
pitting that would indicate weakness of the contact finger
springs.
Inspect the primary disconnect arms for physical integrity
and absence of mechanical damage.
Inspect the flexible connectors that connect the bottom
movable contacts of the vacuum interrupters to the lower
primary disconnect arms for tightness and absence of
mechanical damage, burning, or pitting.
Using a clean cloth saturated with denatured alcohol, clean
old lubricant from primary disconnects, and apply Siemens
contact lubricant (reference 15-171-370-002) in a very thin
layer.
Fastener Check
Inspect all fasteners for tightness. Both lock-nuts and re-
taining rings are used. Replace any fasteners that appear
to have been frequently removed and replaced.
10
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