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2. Abnormal condition and solution
M. Inspection and Troubleshooting
■ Solution for Circuit Breaker’s abnormal condition
Type
Abnormal
Condition
Cause Solution
Temperature
Increase
Terminal unit
Overheating
■ Loose terminal unit tightening screw
■ Faulty booth bar assemble
■ Tightening with designated torque
■ Booth bar reassemble
Product
(except terminal
unit) overheating
■ Faulty contact to internal contactor
■ Current density increase by wire terminal
■ New product replacement
Abnormal
operation
Impossibility of
closing (ON)
■ Foreign substance in switch
■ Reclosing without reset on trip position
■ Remove foreign substance
■ Closing after reset
Impossibility of
reoperating
Impossibility of
Breaking/
OFF Impossibility
■ Worn out by breaking endurance ■ New product exchange
■ Reset device operation fault ■ Request after service
■ The coil of under voltage trip device is not excited. ■ Applying power
■ Switch spring burn out and exhaustion. ■ Replacement and mending
■ Bimetal corrosion and transformation ■ Request after service
■ Reaching the life of switch limit ■ New product exchange
■ Overheating of over current detecting element ■ Operating after cooling
■ Contact meeting and fusion by excessive breaking
current
■ New product exchange
Fault
Current
Flow
Fault
Current
Flow
■ Inflow of insulation material between contact. ■ Remove foreign substance
■ Conductive unit melting
■ New product exchange
■ Contact burn out (wear)
MCCB’s
Frequent
breaking
Break
On normal load
■ Wrong selection of product rating
(causing overheating )
■ No window inside panel (Causing overheating )
■ MCCB internal heating
■ Loose terminal connection unit.
■ New product exchange (rating
reselect )
■ New product exchange
■ Tightening terminal screw (check)
Fault operating
During motor
starting
■ Heating by starting current ■ New product exchange
■ Overload current more than rated current flows.
(when using motor with overload or over voltage )
■ Rating adjustment
Instantaneous
Operation
While
Starting
■ Excessive starting current
■ Instantaneous breaking current
setting or rating adjustment
■ Excessive current Y△ starting switching
■ Excessive current by reversible operation
■ Instantaneous restarting rush current
■Operation by starting current like charging current of
condenser, incandescent electric lamp flow,
charging, etc.
■ Motor’s Layer Short ■ Motor mending
■ Abnormal current flow at the same time with closing ■ Circuit inspection
■ Operating circuit fault connection
Inactivity
Operating current
of rated current
■ Large rated current ■ Select low rated current
■ Current limit break of top fuse or incompatibility
with top circuit breaker
■ Protection cooperation review or
rating adjustment
Short circuit
of
Power side
Inactive operation
over rated
operating current
■ Dust piling up ■ New product exchange
■ Switch side drop away of conductive material ■ New product exchange
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