GE Industrial Solutions EntelliGuard 800–2000 A Frames, 240–600 Vac Maintenance Manual - Manual (Page 30)

EntelliGuard™ 800–2000 A Power Circuit Breakers
Chapter 6. Contact Maintenance
20
6.1 Introduction
Breakers subjected to frequent interruption of high cur-
rents may eventually require replacement of their con-
tacts. The general rule for determining if replacement is
required is the loss of one-half or more of the mass of the
contact tip material. Roughening or light pitting of the
contact surface does not indicate loss of ability to carry or
interrupt current.
When contacts are replaced, they must be adjusted to
ensure that the proper force and contact depression is
developed between the movable and stationary contacts
when the breaker is closed. This is called the wipe adjust-
ment. Wipe is the distance through which the stationary
contacts move when the breaker closes. It is measured
between the point of contact on a stationary contact when
the breaker is open and the position of the same point
when the breaker is closed. The actual wiping motion is
greater than this measurement, since the contacts over-
travel.
The wipe adjustment provides proper depression to assure
full current-carrying capacity without overheating and
influences proper current transfer during interruption of
fault currents. Transfer of the current is the forced
sequential movement from the main to the intermediate
contacts, then to the arcing contacts, to the arc runner,
and finally to the arc chutes, where energy is dissipated
and the arc is extinguished. Contact wipe should be
checked periodically during normal maintenance inspec-
tions and after any overcurrent trip.
CAUTION: Before performing any contact
adjustment or replacement, disable the closing
springs, as described in Section 5.3.
ATTENTION: Avant d’effectuer tout
ajustement ou remplacement de contact,
neutraliser les ressorts de fermeture, tel que
décrit à la Section 5.3.
6.2 Arc Chute Removal and
Replacement
The arc chutes should be removed and inspected at the
regular inspection period. Arc chutes and interphase bar-
riers are available as renewal parts.
The breaker must be removed from its compartment, as
described in Section 5.2, and placed on a suitable work
surface.
There are two types of arc chutes used in these breakers,
depending on frame size.
Arc Chutes in EGS08, EGF08, and EGH08
Breakers
Use the following procedure to remove and replace the
arc chutes, as illustrated in Figure 8.
1. Verify that the breaker contacts are open and the
closing springs are discharged.
2. Remove the mounting bolt and lock washer secur-
ing each of the arc chutes and lift out the arc
chutes. Remove the four interphase barriers.
3. Check the arc chutes and barriers for damage and
replace them, if necessary.
4. Replace the four interphase barriers into their slots.
5. Slide the arc chutes into place, with the slots over
the movable contact arms.
6. Replace the mounting bolt and lock washer secur-
ing each arc chute to the breaker frame.
CAUTION: All insulating barriers must be in
place before the breaker is placed back into
service.
ATTENTION: Toutes les barriéres isolatrices
doivent être en place avant que le disjoncteur
ne soit replacé en service.
Arc Chutes in EGX08, EGS16, EGF16,
EGH16, EGS20, and EGF20 Breakers
Use the following procedure to remove and replace the
arc chutes, as illustrated in Figure 10.
1. Verify that the breaker contacts are open and the
closing springs are discharged.
2. Remove the two bolts and lock washers that attach
the arc chute retainer to the front frame and
remove the retainer.
3. Slide out the arc chutes and interphase barriers.
Note that there are three distinct types of phase bar-
riers: right, inner (2), and left.
4. Check the arc chutes and barriers for damage and
replace them, if necessary.
5. Replace the four interphase barriers into their cor-
rect slots.
6. Slide the arc chutes into place, with the slots over
the movable contact arms.
7. Replace the arc chute retainer bar and secure it with
two bolts and lock washers.
CAUTION: All insulating barriers must be in
place before the breaker is placed back into
service.