Fastener Check; Manual Spring Changing And Contact Erosion Checks - Siemens SGIM-3268H Manual

Figure 34: Front View of Operator Mechanism.
Typical circuit breaker with
vacuum interrupter having
external arc chamber
Figure 35: Contact Erosion Check Mark.
Courtesy of NationalSwitchgear.com
Typical circuit breaker with
vacuum interrupter having
internal arc shield

Fastener Check

Inspect all fasteners for tightness. Both lock-nuts and
retaining rings are used. Replace any fasteners that appear
to have been frequently removed and replaced.
Manual Spring Charging and Contact Erosion Checks
Perform the Manual Spring Charging Check contained in
the section describing the Installation Check and Initial
Functional Tests. The key steps of this procedure are
repeated here.
1. Insert the hand charging lever into the manual charge
handle socket at the front of the operator control
panel. Figure 20 shows the lever inserted. Up and
down motion of the lever charges the closing springs.
Continue cranking until the Charged flag appears in
the window of the spring indicator.
2. Press the Close (black) pushbutton. The contact
position indicator on the operator control panel should
indicate that the circuit breaker contacts are closed.
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 shown in Figure 36. The white erosion
mark is located in the keyway (or slot) on the movable
stem of the vacuum interrupter, near the plastic guide
bushing.
The contact erosion check procedure is:
• Be sure the breaker primary contacts are Closed.
• Observe the white erosion mark (Figure 36) of each
pole. When this mark is visible, contact wear is
within acceptable limits. For some circuit breakers
(with a vacuum interrupter having an internal arc
shield), a flashlight and dental mirror will be needed
to observe the white erosion mark.
Tripping spring is charged.
If trip latch is moved, high-speed movement
of components can cause serious injury.
Observe precautions concerning physical
contact with components of the circuit breaker
subjected to sudden, high speed movement.
4. Press the red Trip pushbutton after completing the
contact erosion check. Visually verify the Discharge
condition of the closing springs and that 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 mechanism.
Maintenance
WARNING
27