Masterpact ® circuit breaker
appendix
A
DANGER
HAZARD OF ELECTRICAL SHOCK,
BURN OR EXPLOSION
Turn OFF all power supplying the
equipment before installing or removing
circuit breaker.
Failure to observe these precautions will
cause death, personal injury or
electrical shock.
recommended inspection
intervals
MasterpacfiD circuit breakers are designed to
be maintenance-free (see page 38).
However, all equipment with moving parts
requires periodic inspection to ensure
optimum performance and reliability. We
recommend that the circuit breakers be
routinely inspected six months after
installation, followed by an annual
inspection. Intervals can vary depending on
your particular use and experience.
inspection of terminals
Connections of circuit breaker:
•
inspect terminals. If there is discoloration
due to overheating, the joint should be
dissassembled and the surface cleaned
before reinstallation.
It is essential that electrical connections are
made carefully in order to prevent
overheating.
•
check for terminal tightness.
i nspection of main contacts
The arc chutes are easily removable to allow
access to the main contacts and to the wear
indicator. The wear indicator consists of a
groove located within the contacts support
(see page 3). When the circuit breaker is
closed, this groove is entirely covered up by
the moving contacts.
Over time, the wear of the contacts will
make the groove appear.
The contacts will have to be changed when
the groove is fully visible.
i nspection of clusters
Placed in the cradle, and not on the moving
portion, the clusters are protected against
damage due to handling during servicing.
Totally maintenance-free, they have to be
replaced only after overheating due to a
defective connection or after a major fault.
Inspection is advised when checking the
terminal connections.
cleaning
Remove the dust and dirt that may have
accumulated on the circuit breaker surface
and terminals.
mechanical checks
For long periods circuit breakers may not be
required to operate on overload or short
circuit conditions. Therefore it is essential to
operate the circuit breaker periodically to
avoid mechanical gumming.
insulation resistance tests
When circuit breakers are subjected to
severe operating conditions, an insulation
resistance test may be performed as
indicated in NEMA standard publication
No. AB4- 1 991 .
An insulation resistance test is used to
determine the quality of the insulation
between phases and phase-to-ground. The
resistance test is made at a de voltage
higher than the rated voltage to determine
the actual resistance of the insulation. The
most common method employs a "megger"
type instrument. A 1 000-volt instrument will
provide a more reliable test because it is
capable of detecting tracking on insulated
surfaces. Resistance values below 1
megohm should be investigated.
The insulation test shall be made:
routine maintenance
g uidelines
•
between line and load terminals of
individual poles with the circuit breaker
contacts open.
•
between adjacent poles and from poles to
the metallic supporting structure with the
circuit breaker contacts closed. This test
may be made with the circuit breaker in
place after the line and load conductors
have been removed, or with the circuit
breaker bolted to a metallic base which
simulates the in-service mounting.
electrical tests
These tests require equipment for pole
resistance measurement and for overcurrent
and instantaneous tripping in accordance
with NEMA standard publication No. AB4.
They are not within the scope of normal field
operation.
CAUTION
HAZARD OF EQUIPMENT DAMAGE
Since circuit breakers contain
factory-sealed and calibrated elements.
Do not break seal. In case of
malfunction, repairs must be made at a
Merlin Gerin factory or by an authorized
representative.
Failure to observe this precaution may
cause equipment damage.
37
www
. ElectricalPartManuals
. com
