Slide 1

Commissioning, operation & Maintenance of low voltage air circuit breakers Position of main contacts of breaker is indicated by an indicator which is visible through a transparent window on the breaker front facia as under:Main contacts closed RED Colour with ONMain contacts open Green Colour with OFF Always wear protective equipment while carrying out breaker operations when power supply is on Ensure presence of power supply if breaker is fitted with under voltage release OPERATION OF ELECTRICALLY OPERATED BREAKERSIN ELECTRICALLY OPERATED BREAKERS, ELECTRIC MOTOR IS USED FOR CHARGING THE SPRINGS. THE OPERATING SEQUENCE IS AS UNDER: MOTOR CHARGES THE CLOSING SPRING SUPPLY TO MOTOR GETS DISCONNECTED AT THE END OF CHARGING OPERATION CLOSING ELECTROMAGNET, WHEN ACTUATED, DISCHARGES THE SPRINGS AND CLOSES THE BREAKERAFTER BREAKER CLOSES, THE SPRING AUTOMATICALLY GET CHARGED FOR NEXT CLOSING OPERATION ON/ OFF INDICATIONS APPEAR SPRING CONDITION, CHARGED/DISCHARGED IS INDICATED BY A MECHANICAL INDICATOR, VISIBLE FROM TRANSPARENT WIDOW ON THE FRONT FACIA AS UNDER;

SPRING CHARGED YELLOWSPRINGS DISCHARGED BLACK IN CASE OF NON AVAILABILITY OF CONTROL POWER SUPPLY TO SPRING CHARGING MOTOR, SPRINGS CAN BE CHARGED MANUALLY BY OPERATING HANDLE AFTER THE SPRINGS ARE CHARGED, THE BREAKER CAN BE CLOSED BY ACTUATING CLOSING PUSH BUTTON SPRING CHARGING MECHANISM SPRING CHARGING MECHANISM SPRING CHARGING MOTORS ARE RATED FOR 240V AC, 220V DC AND 110V DC VOLTAGE MOTORS ARE RATED TO OPERATE WITHIN 85-110% OF RATED VOLTAGE SPRING CHARGING TIME IS APPROXIMATELY 7 SECONDS POWER CONSUMPTION OF SPRING CHARGING MOTOR IS 300 VA FOR 240 V AC AND 154 WATTS FOR DCCLOSING ELECTROMAGNET

CLOSING ELECTROMAGNET PROVIDED FOR RELEASING THE SPRINGS AND CLOSING BREAKER IS RATED FOR 240VAC, 220V DC AND 110V DC CLOSING ELECTROMAGNET ARE RATED TO OPERATE WITHIN 85-110% OF RATED VOLTAGECLOSING TIME IS APPROXIMATELY 70 MILLISECONDS IN CASE OF DC VOLTAGE, ECONOMY RESISTORS ARE WIRED IN SERIES WITH THE CLOSING ELECTROMAGNETPOWER CONSUMPTION OF SPRING CHARGING MOTOR TYPICALLY IS APPROX. 300 VA FOR 240 V AC APPROX. 154 WATTS FOR DCIN CASE OF DC VOLTAGE, ECONOMY RESISTORS ARE WIRED IN SERIES WITH THE CLOSING ELECTROMAGNET

AFTER CLOSE OPEN CYCLE IT IS NOT POSSIBLE TO RECLOSE THE BREAKER AS LONG AS THE CLOSING COMMAND IS MAINTAINED. THIS FEATURE IS KNOWN AS ANTI PUMPING, IS ASSURED MECHANICALLY AND ELECTRICALLY, BOTH IN LOCAL AND REMOTE OPERATIONS. FOR RECLOSING THE BREAKER, THE PERMANENT CLOSING COMMAND SHOULD BE MOMENTARILY INTERRUPTED . THIS IS CALLED ANTIPUMPING FATURE OF CIRCUIT BREAKERTHE MOVING CONTACTS OF BREAKER RETURN AND REMAIN IN OPEN POSITION WHEN OPENING OPERATION IS INITIATED AFTER INITIATION OF CLOSING COMMAND. IN THIS CASE THE CLOSING COMMAND IS OVERRULED BY OPENING COMMAND. THIS IS CALLED TRIP FREE FEATUREWHEN BREAKER IS WITHDRAWN FROM SERVICE POSITION WITH MAIN CONTACTS CLOSED, THE DEVICE AUTOMATICALLY TRIP THE BREAKER BEFORE SEPARATION OF MAIN ISOLATING CONTACTS. OR BEFORE THEY COME INTO CONTACT DURING INSERTIONWhen racking interlock is provided, key of the lock has to be pressed and turned anti clockwise. This will trip breaker if it is in closed condition at any location between test and service position Cradle is provided with door interlocking, ensure that door is closed or door interlock is defeated OVER LOAD AND SHORT CIRCUIT THERMO MAGNETIC RELEASE This release provides protection against short circuit for which electromagnets are provided with two taps for selecting the operating current of the order of 6 In and 7.5 In Magnetic release incorporates definite mimum operating time of 25 milliseconds, which is independent of maThree bi metallic strips give protection against over loads. These are individually adjustable on the front facia by means of pointer from 0.75In to 1.0 In In case of breakers with local reset feature, tripping through the release leaves the latch of the mechanism open hence resetting with the help of TRIP/RESET or TRIP/LOCK/RESET push button is necessary, prior to subsequent opening operationRelease is also provided with a strip for manual tripping. Pressing the strip will release the mechanical latch of the release and trip the breakerRelease has inverse thermal time current characteristics on over loadOnly over current and only short circuit protection can be provided on the release by adopting appropriate connections

MICRO PROCESSOR BASED OVER CURRENT, SHORT CIRCUIT AND EARTH FAULT RELEASERelease is fed by single tap current transformer of same rating as that of circuit breaker InSetting range available are: i)Long time- Pick up current adjustable between 0.5 to 1.0 In , time delay adjustable between 0.2 to 30 seconds at 6In ii) Short time- pick up current adjustable between 2 to 10 times In, time delay 20milliseconds to 600 milliseconds iii) Earth fault pick up current adjustable between 0.2 to 0.6 In, time delay adjustable between100 milliseconds to 400 milliseconds iv) Instantaneous pick up adjustable between 2 to 16 times In, time delay fixed 20 +/- 5 millisecondsRotary switches are used to adjust the settings Red knob for pickup and Blue knob for time delayThe release has thermal memory, as when thr breaker trips under long time protection, the cooling time allowed affects the subsequent trip time when breaker is reenergized under fault condition. This feature can be switched off by ON/OFF sliding switch on the faciaLED indicators are provided for displaying the types of faults which has caused the tripping of the breaker. This lasts for maximum 72 hours and remains so till it is cleared by CLEAR push button

Test push button is used to verify validiation of hardware and software, internally, checking whether the trip unit is healthy or not. When pressed, power ON LED change from blinking red to steady greenDuring the time the Test push button is pressed, all protections are still available and neither affected nor defeated