Figure 40: Contact-erosion check
mark dot circled in orange (shown
with circuit breaker OPEN)
Primary-disconnect contacts (multi-
fingered clusters) and secondary-
disconnect contacts (strips and fingers) are
to be wiped clean, and a film of Siemens
contact lubricant (15-172-791-233)
applied. Avoid getting contact lubricant on
any insulating materials.
Inspect all fasteners for tightness. Both
locknuts and retaining rings are used.
Replace any fasteners that appear to have
been frequently removed and replaced.
Manual-spring charging and contact-
Perform the manual-spring charging check
contained on page 12 in the section
"Installation check and initial functional
tests." The key steps of this procedure are
1. Insert the hand-charging crank into the
manual-charge socket at the front of
the operator control-panel. Turn the
crank clockwise (about 48 revolutions)
to charge the closing spring. Continue
cranking until the CHARGED flag
appears in the window of the spring-
2. Press the close (black) pushbutton. The
contact-position indicator on the
operator-control panel should indicate
the circuit-breaker contacts are
3. Perform the contact-erosion check.
Contact erosion occurs when high-fault
currents are interrupted or when the
vacuum interrupter is nearing the limit
of its contact life. Determination of
acceptable contact condition is
checked by the visibility of the white-
erosion mark (refer to Figure 40:
Contact-erosion check mark dot circled
in orange (shown with circuit breaker
OPEN)). The white-erosion mark is
located in the keyway (or slot) on the
movable stem of the vacuum
interrupter, near the plastic-guide
The contact-erosion check procedure is:
A. Be sure the circuit-breaker primary
contacts are CLOSED.
B. Observe the white-erosion mark of
each pole (refer to Figure 36: Trip-
control pushbutton (lower button)
on page 43). When this mark is
visible, contact wear is within
4. Press the red trip pushbutton after
completing the contact-erosion check.
Visually verify the DISCHARGED
condition of the closing springs and
the circuit-breaker contacts are OPEN.
5. Press the black close pushbutton.
Nothing should happen. The manual-
spring check should demonstrate
smooth operation of the operating
High-speed moving parts.
Can result in serious injury.
Tripping spring is charged. If trip latch is moved, the stored-
energy springs will discharge rapidly.
Stay clear of circuit breaker components subject to sudden, high-