Eaton 50VCPW-ND250 Installation, Operation And Maintenance Manual

Also see for 120VCP-W25: Instructions for installation/operation/maintenance/servicing Instructions for installation, operation and maintenance

Contents

I.B. 32-255-1G Page 23Effective 12/02At current zero, the arc is extinguished and vapor produc-tion ceases. Very rapid dispersion, cooling, recombina-tion, and deionization of the metal vapor plasma, togetherwith the fast condensation of metal vapor products, causethe vacuum to be quickly restored. Hence, the openedcontacts withstand the transient recovery voltage.5-2.2 CONTACT EROSION INDICATIONThe purpose of a contact erosion indicator is to monitorthe erosion of the vacuum interrupter contacts, which isvery minimal over time with vacuum interrupters utilizingcopper-chrome contact material. If contact erosionreaches 1/8 inch, the interrupter must be replaced. Agreen contact erosion indicator mark is located on themoving stem of the interrupter (Figures 6-2 and 6-3).In order to determine if the contacts have eroded to theextent that the interrupter must be replaced, observe theerosion mark placed on each moving stem from the rearof the breaker with the breaker closed. The interrupter issatisfactory if the mark on the stem is visible with thebreaker closed. The entire interrupter assembly must bereplaced if the mark is no longer visible.5-2.3 LOADING SPRING INDICATORThe loading spring indicator is an additional method pro-vided to indicate conditions within the interrupter. Theindicator is used to indicate whether the contact springsare maintaining the adequate contact pressure to keepthe contacts closed. Severe contact erosion would resultin an unacceptable indication from the indicator (Figure6-4). Depending upon the structural design, a smallmirror may be required to inspect all three poles.Note that the actual configuration and/or appearance ofthe indicator can vary from one circuit breaker rating toanother. The actual appearance of the indicatordepends upon the color of the contact springs in a spe-cific circuit breaker. When making this inspection, firstobserve the color of the contact springs to determinehow the indicator will appear. Figure 6-4 illustrates whatthe actual indicator appearance will be, depending uponthe color of the springs.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 VCP-W vacuum circuit breakers in order toeliminate the need for field adjustments of wipe or 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.5-2.5 PHASE BARRIERSPhase barriers on all VCP-W circuit breakers are madeof glass polyester. Table 5.1 gives the number and con-figuration of the barriers required for each circuit breakerrating.InterruptionCurrentZeroShield InvolvementHigh CurrentArc ModeArcInitiationRecoveryVoltageFaultCurrentFigure 5-2 Graphic Representation of Arc Interruption! CAUTION