27
I.B. 8926-1A
=
Reproduced by permission of the National Electrical Manufacturers Association from NEMA Standards Publication No. ICS 2-
1978 (R1983), Industrial Control Devices, Controllers and Assemblies, copyright 1978 by NEMA.
replacements made before re-energizing the branch
circuit.
It is recommended that the following general
procedures be observed by qualified personnel in
the inspection and repair of the motor controller
involved in the fault.
Procedure – Caution: All inspections and tests
are to be made on controllers and equipment
which are de-energized, disconnected and
isolated so that accidental contact cannot be
made with live parts and so that all plant safety
procedures will be observed.
Enclosure.
Substantial damage to the unit door or
frame such as deformation, displacement of parts or
burning, requires replacement of the entire unit.
Circuit breaker.
Examine the unit interior and the
circuit breaker for evidence of possible damage. If
evidence of damage is not apparent, the breaker
may be reset and turned ON. If it is suspected that
the circuit breaker has opened several short-circuit
faults or if signs of circuit breaker deterioration
appear within the enclosure, the circuit breaker
should be replaced.
Disconnect switch.
The external operating handle
of the disconnect switch must be capable of opening
the switch. If the handle fails to open the switch or if
visual inspection after opening indicates
deterioration beyond normal wear and tear, such as
overheating, contact blade or jaw pitting, insulation
breakage or charring, the switch must be replaced.
Fuse holders.
Deterioration of fuse holders or their
insulating mounts requires their replacement.
Terminals and internal conductors.
Indications of
arcing damage and/or overheating such as
discoloration and melting of insulation require the
replacement of damaged parts.
Contactor.
Contacts showing heat damage,
displacement of metal, or loss of adequate wear
allowance require replacement of the contacts and
the contact springs. If deterioration extends beyond
the contacts, such as binding in the guides or
evidence of insulation damage, the damaged parts
or the entire contactor must be replaced.
Overload relays.
If burnout of the current element
of an overload relay has occurred, the complete
overload relay must be replaced. Any indication that
an arc has struck and/or any indication of burning of
the insulation of the overload relay also requires
replacement of the overload relay.
If there is no visual indication of damage that would
require replacement of the overload relay, the relay
must be electrically or mechanically tripped to verify
the proper functioning of the overload relay
contact(s).
Return to service.
Before returning the controller to
service, checks must be made for the tightness of
electrical connections and for the absence of short
circuits, grounds an leakage.
All equipment enclosures must be closed and
secured before the branch circuit is energized.
Fig. 39 Normal Service Wear
Fig. 40 End of Service Life
