IB131021EN
Page xxv
Effective Mar 2018
Figure 5-2 Graphic Representation of Arc Interruption
At current zero, the arc is extinguished and vapor production
ceases. Very rapid dispersion, cooling, recombination, and
deionization of the metal vapor plasma, together with the
fast condensation of metal vapor products, cause the
vacuum to be quickly restored. Hence, the opened
contacts withstand the transient recovery voltage.
5-2.2
CONTACT WIPE AND STROKE
Contact wipe is the indication of (1) the force holding the
vacuum interrupter contacts closed and (2) the energy
available to “hammer” the contacts open with sufficient
speed for interruption.
Stroke is the gap between fixed and moving contacts of a
vacuum interrupter with the circuit breaker open.
The circuit breaker mechanism provides a fixed amount
of motion to the operating drive rods. The first portion of
the motion is used to close the contacts (stroke) and the
remainder is used to further compress the preloaded
contact springs. This additional compression is called
wipe. Wipe and Stroke are thus related to each other. As
the stroke increases due to the erosion of contacts, the
wipe decreases.
Contact wipe can be calculated by measuring the distance
between the Drive Rod End and the Drive Rod Housing
(Figure
5-3
) in both the “open” and “closed” state and
subtracting the “closed” measurement from the “open”
measurement. Contact wipe is factory set to 0.217” +/-
0.010” on each phase.
The contact wipe should be rechecked during standard
inspection and maintenance intervals as discussed in
Section 6 of this document to ensure it is within the specified
limits on each phase. The contact wipe can be increased if
it has been reduced by contact erosion.
To increase contact wipe on a pole unit/ drive rod assembly,
follow these steps:
Measure distance between the Drive Rod End and
1.
the Drive Rod Housing in the “open” and “closed”
state and subtract the “closed” measurement from
the “open” measurement to calculate the Wipe.
Determine how much the wipe needs to be
2.
increased to meet the desired specification: 0.217”
+/- 0.010”
Loosen the M10 Jam Nut nearest to the Tie Bar
3.
(Figure
5-4
)
Rotate the Drive Rod Housing clockwise (if looking
4.
at the front of the circuit breaker) to move the Drive
Rod Housing closer to the Vacuum Interrupter and
increase the spring compression (Wipe)
Calculate how much to rotate the Drive Rod
5.
Housing by taking into account the M10 x 1.5 thread
pitch
Thread pitch = 1.5mm = .059”. So, one full
a.
rotation of the Drive Rod Housing will
increase the Contact Wipe by .059”; one
half rotation of the Drive Rod Housing will
increase the Contact Wipe by .0295”; etc.
Once Drive Rod Housing is adjusted desired
6.
amount, retighten M10 Jam Nut nearest to Tie Bar
and recalculate the Wipe per step 1.
Repeat steps 1-6 as needed until the Contact Wipe
7.
is adjusted to meet the desired specification: 0.217”
+/- 0.010” for all three phases.
Note: If Contact Wipe is accidentally adjusted above
specified limit, it can be reduced by loosening the M10
jam nut nearest to the Tie Bar and rotating the Drive
Rod Housing counter clockwise (if looking at the front of
the circuit breaker).
