17
THE UNDERVOLTAGE TRIP IS MOUNTED ON THE LEFT HAND
MECHANISM SIDEPLATE AND ACTS DIRECTLY ON THE BREAKER'S
LEFT TRIP SHAFT LEVER.
IT IS IDENTIFIED BY THE SYMBOL "NV" ON THE WIRING DIAGRAM.
REFER TO SECTION 8.6 FOR ILLUSTRATION AND ADJUSTMENTS.
5.5 SAFETY INTERLOCK SWITCH (SIS)
THE SAFETY INTERLOCK SWITCH PROVIDES ADDITIONAL
SAFETY AGAINST PARALLELING TWO OR MORE BREAKERS USED IN
TRANSFER SCHEMES, ETC. THE SWITCH IS OPERATED BY THE CLOSE
LATCH RELEASE MECHANISM. ITS NORMALLY OPEN CONTACT IS
WIRED IN PARALLEL WITH THE NORMALLY OPEN SHUNT TRIP COIL
CLEARING CONTACT. IT MUST BE CONNECTED IN SERIES WITH A
NORMALLY OPEN AUXILIARY SWITCH CONTACT FROM THE OTHER
BREAKER BEING INTERLOCKED. WITH THE ALTERNATE BREAKER
CLOSED ATTEMPTS TO CLOSE THIS BREAKER BY MEANS OF THE
MANUAL CLOSE BUTTON OR EMERGENCY HANDLE WILL CLOSE SIS
CONTACT AND ENERGIZE
THE SHUNT TRIP COIL. THIS OPERATES THE
BREAKER TRIP SHAFT BEFORE THE CLOSING SPRING IS RELEASED
RESULTING IN DRY RUN AND PREVENTS THE BREAKER FROM
CLOSING. NO ADJUSTMENT IS REQUIRED FOR THIS DEVICE. IT IS
IDENTIFIED BY THE SYMBOL "SIS" ON THE WIRING DIAGRAM, WHILE
THE NORMALLY OPEN AUXILIARY SWITCH CONTACT Of THE
ALTERNATE BREAKER IS IDENTIFIED BY THE SYMBOL "52-A".
FIG. 5.5 SAFETY INTERLOCK SWITCH
5.6 OVERLOAD LOCKOUT DEVICE
THE OVERLOAD LOCKOUT DEVICE PREVENTS RECLOSING OF THE
BREAKER EITHER MANUALLY OR ELECTRICALLY AFTER THE
BREAKER HAS BEEN TRIPPED BY THE OVERLOAD RELAY UNTIL THIS
DEVICE IS MANUALLY RESET.
FIG. 5.6 OVERLOAD LOCKOUT
(SHOWN IN OPERATED OR TRIP FREE POSITON)
1.
TRIP COIL
2.
FAULT INDICATION SWITCH
3.
RESET BUTTON
5.7 DOOR INTERLOCK
ALL BREAKERS MAY BE FITTED WITH A DEVICE WHICH ACTS
TO TRIP THE BREAKER WHEN THE CELL DOOR IS OPENED. IN
OPERATION, THE INTERLOCK LEVER ACTS INTERNALLY ON THE
MANUAL TRIP BUTTON CAUSING IT TO BE DEPRESSED AND TRIP THE
BREAKER. THIS INTERLOCK MAY BE DEFEATED BY ARRESTING THE
MOVEMENT OF THE TRIP BUTTON. A SCREWDRIVE BLADE OR SIMILAR
TOOL INSERTED THROUGH THE SLOT IN THE TRIP BUTTON WILL
ALLOW THE DOOR TO BE OPENED WITHOUT TRIPPING THE CIRCUIT
BREAKER.
A SPECIAL USD RELAY TRIP COIL IS INSTALLED WITH THIS
DEVICE, ALONG WITH A SPRING OPERATED MECHANISM LINKING THE
TRIP COIL WITH THE MANUAL RESET BUTTON ON THE BREAKER
FACEPLATE. WHEN THE TRIP COIL IS ENERGIZED, IT TRIPS THE
BREAKER AND AT THE SAME TIME THE SPRING MECHANISM POPS THE
RESET BUTTON OUT ON THE FACEPLATE AND HOLDS THE TRIP COIL
PLUNGER UP, SO THAT THE BREAKER IS IN A TRIP-FREE STATE.
ON ELECTRICALLY OPERATED BREAKERS, THE LATCH CHECK
SWITCH WILL PREVENT OPERATION OF THE CLOSE COIL AND ANY
ATTEMPT TO MANUALLY CLOSE THE BREAKER WILL RESULT IN A
DRY RUN.
ONE SPDT SWITCH CAN BE PROVIDED WITH THIS DEVICE FOR
FAULT INDICATION. THESE CONTACTS ARE IDENTIFIED BY THE
SYMBOL "FI" ON THE WIRING DIAGRAM.
