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

I.B. 3A74791H04Page 20Effective 7/97rotate the closing spring cranks and the closing camwith it.The closing spring cranks have spring ends connectedto them, which are in turn coupled to the closing springs.As the cranks rotate, the closing springs are charged.When the closing springs are completely charged, thespring cranks go over dead center, and the closing stoproller comes against the spring release latch. The clos-ing springs are now held in the fully charged position.Closing springs may also be charged manually. Insertthe maintenance tool in the manual charging socket.Move it up and down approximately 38 times until aclicking sound is heard, and the closing springs charg-ing indicator indicates “Charged.” Any further motion ofthe maintenance tool will result in free wheeling of theratchet wheel.5-3.3 CLOSING OPERATIONFigure 5-4 shows the position of the closing cam andtripping linkage. Note that in Figure 5-4a in which thecircuit breaker is open and the closing springs are dis-charged, the trip “D” shaft and trip latch are in theunlatched position.Once charged, the closing springs can be released toclose the circuit breaker by moving the spring releaselatch out of the way. This is done electrically or manuallyby depressing the spring release lever, which turns thespring release latch out of the way of the closing stoproller. The force of the closing spring rotates the camshaft through the spring cranks. The closing cam, beingattached to the cam shaft, in turn rotates the pole shaftthrough the main link to close the circuit breaker.In Figure 5-4c the linkage is shown with the circuitbreaker in the closed position before the closing springshave been recharged. Interference of the trip “D” shaftwith the trip latch prevents the linkage from collapsing,and the circuit breaker is held closed.Figure 5-4d shows the circuit breaker in the closed posi-tion after the closing springs have been recharged. Notethat the spring charging rotates the closing cam by onehalf turn. Since the cam surface in contact with the mainlink roller is cylindrical in this region, the spring chargingoperation does not affect the mechanism linkage.Since the primary contacts are completely enclosed inthe vacuum interrupter and not adjustable in any way, a“Slow Close” capability is not provided with W-VAC cir-cuit breakers.5-3.4 TRIPPING OPERATIONWhen the trip “D” shaft is turned either by the trip buttonor trip coil, all links return to the original “open” conditionshown in Figure 5-4a.5-4 CONTROL SCHEMESThere are two basic control schemes for 36kV W-VACcircuit breakers, one for DC control and one for AC con-trol voltages (Figure 5-6). There may be different controlvoltages or more than one tripping element, but the prin-cipal mode of operation is as follows:As soon as the control power is applied, the springcharging motor automatically starts charging the closingsprings. When the springs are charged, the motor cut offLS1/bb switch turns the motor off. The circuit breakermay be closed by making the control switch close(CS/C) contact. Automatically upon closing of the circuitbreaker, the motor starts charging the closing springs.The circuit breaker may be tripped any time by makingthe control switch trip (CS/T) contact.Note the position switch (PS1) contact in the springrelease circuit in the scheme. This contact remainsmade while the circuit breaker is being levered betweenthe TEST and CONNECTED positions. Consequently, itprevents the circuit breaker from closing automatically,even though the control close contact (CS/C) may havebeen made while the circuit breaker is levered to theCONNECTED position.The position switch (PS2) contact is in the motor circuit.It prevents the motor from starting until the fully CON-NECTED position is reached and the secondary con-tacts are firmly engaged.When the CS/C contact is made, the SR closes the cir-cuit breaker. If the CS/C contact is maintained after thecircuit breaker closes, the Y relay is picked up. The Y/acontact seals in Y until CS/C is opened. The Y/b contactopens the SR circuit, so that even though the circuitbreaker would subsequently open, it could not bereclosed before CS/C was released and remade. This isthe anti-pump function.5-4.1 TIMINGThe opening and closing times for the circuit breakersvary depending upon the control voltage and the powerrating. Typical values for 36kV W-VAC circuit breakersare shown in Table 5.1.