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CONTACTOR TROUBLESHOOTING CHART (Cont.)
Defect
Overheating
Ambient temperature is
too high
Line and/or cables are too
small
Welding of
Excessive contact bounce
contacts
on closing
Jogging duty is too severe
Excessive inrush current
Vibration in starter mounting
MAINTENANCE OF MOTOR CONTROLLERS AFTER
A FAULT
In a motor branch circuit which has been properly in-
stalled, coordinated and in service prior to the fault, open-
ing of the branch-circuit short-circuit protective device
(fuse, circuit breaker, motor short-circuit protector, etc.)
indicates a fault condition in excess of operating over-
load. This fault condition must be corrected and the
necessary repairs or replacements made before reener-
gizing 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
deenergized, disconnected and isolated so that ac-
cidental 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 cir-
Reproduced by permission of the National Electrical Manufacturers Association from NEMA Standards Publication No. ICS
2-1978 (Rl983), Industrial Control Devices, Controllers and Assemblies, copyright 1978 by NEMA.
Cause
Remedy
Reduce load. Privde better ventilation. Relocate starter. Use larger
block and run larger conductors betwee contactor and terminal block.
Correct coil overvoltage condition
Reduce jogging cycle
Motor has locked rotor code letter greater than G. Most contactors
are designed for motors with code letters A through G. therefore,
use larger contactor. check factory for weld-resistant contact mate-
rial.
Move starter to location having less shock and vibration. Insualte
starter from shcock and vibration. Privde more rigid support for
starters
cuit breaker for evidence of possible damage. If evi-
dence 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 enclo-
sure, 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 theii in-
sulating mounts requires their replacement.
Terminals and internal conductors. Indications ot arc-
ing damage and/or overheating such as discoloration and
melting of insulation require the replacement of dam-
aged parts.
Contactor. Contacts showing heat damage, displace-
ment of metal, or loss of adequate wear allowance re-
quire replacement of the contacts and the contact
springs. If deterioration extends beyond the contacts,
such as binding in the guides or evidence of insulation
- Page 29 -
I.B. 8926-1
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