Eaton Cutler-Hammer W-VAC Instructions For Installation, Operation And Maintenance

I.B. 3A74791H04Page 18Effective 7/97mark is located on the insulated operating rod of eachinterrupter (Figures 6-2 and 6-3).A second more convenient indicator is located on thefront of the circuit breaker (Figure 3-4). Small viewingwindows located on the front lower portion of the circuitbreaker truck provide a green and red “Go” or “No Go”flag indication of each vacuum interrupter’s contact ero-sion condition. This indicator is provided as a conve-nient reference when the circuit breaker is installed in itscubicle. As long as the line in the window is in the greenportion of the indicator, the contacts are satisfactory.When the line reaches the red portion of the indicator,the interrupter assembly must be replaced.5-2.3 LOADING SPRING INDICATIONThe contact loading spring indicator is an additionalmethod provided to indicate conditions within the vacuuminterrupter, as well as the overall system condition. The vis-ible indication, on each phase, is used to indicate whetherthe contact loading springs are maintaining the proper con-tact pressure to keep the contacts closed. Severe contacterosion or an adjustment need after an interrupter assem-bly replacement would result in an unacceptable indicationfrom this indicator (Figures 6-4 and 6-5).5-2.4 CONTACT WIPE AND STROKEContact wipe is the indication of (1) the force holding thevacuum interrupter contacts closed and (2) the energyavailable to hammer the contacts open with sufficientspeed for interruption.Stroke is the gap between fixed and moving contacts ofa vacuum interrupter with the circuit breaker open.The circuit breaker mechanism provides a fixed amountof motion to the operating rods. The first portion of themotion is used to close the contacts (i.e. stroke) and theremainder is used to further compress the preloadedwipe spring. This additional compression is called wipe.Wipe and Stroke are thus related to each other. As thestroke increases due to the erosion of contacts, the wipedecreases. A great deal of effort has been spent in thedesign of all Cutler-Hammer vacuum circuit breakers, inorder to eliminate the need for field adjustments of wipeor stroke.THERE IS NO PROVISION FOR IN SERVICEADJUSTMENTS OF CONTACT WIPE AND STROKE.ALL SUCH ADJUSTMENTS ARE FACTORY SETAND SHOULD NOT BE ATTEMPTED IN THE FIELD.5-3 STORED ENERGY MECHANISMKEEP HANDS AND FINGERS AWAY FROM THE CIR-CUIT BREAKER’S INTERNAL PARTS WHILE THECIRCUIT BREAKER CONTACTS ARE CLOSED ORTHE CLOSING SPRINGS ARE CHARGED. THE CIR-CUIT BREAKER CONTACTS MAY OPEN OR THECLOSING SPRINGS DISCHARGE CAUSING ACRUSHING INJURY. DISCHARGE THE SPRINGSAND OPEN THE CIRCUIT BREAKERS BEFORE PER-FORMING ANY CIRCUIT BREAKER MAINTENANCE,INSPECTION OR REPAIR.The spring stored energy operating mechanism isarranged vertically in front of all W-VAC circuit breakers(Figure 3-5). It includes all the elements for storing theenergy, closing and tripping of the circuit breaker, aswell as manual and electrical controls. The manual con-trols are all front accessible. Motion to close and openthe interrupter contacts is provided through operatingrods connecting the mechanism pole shaft to the bellcranks of the interrupter assemblies.5-3.1 OPERATION OF STORED ENERGYMECHANISMThe mechanism stores the closing energy by chargingthe closing springs. The mechanism may rest in any oneof the four positions shown in Figure 5-4 and as follows:a. Circuit breaker open, closing springs dischargedb. Circuit breaker open, closing springs chargedc. Circuit breaker closed, closing springs dischargedd. Circuit breaker closed, closing springs charged5-3.2 CHARGINGFigure 5-5 is a schematic view of the spring chargingparts of the stored energy mechanism.The major component of the mechanism is a cam shaftassembly which consists of a drive shaft to which areattached two closing spring cranks (one on each end),the closing cam, drive plates, and a free-wheeling ratch-et wheel. The ratchet wheel is actuated by an oscillatingmechanism driven by the motor eccentric. As the ratchetwheel rotates, it pushes the drive plates which in turn! WARNING! CAUTION