Eaton VCP-W Series Instructions For Installation/operation/maintenance/servicing

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

Contents

37Instruction Booklet IB131006ENEffective March 2019Instructions for installation,operation, and maintenance of typeVCP-W vacuum circuit breakersEATON www.eaton.comDirect acting insulated operating rods in conjunction with the circuitbreaker’s mechanism provide a fixed amount of interrupter movablestem motion. This motion is directly related to the interrupter’s“wipe” and “stroke,” each of which is discussed in detail later in thissection.5.2.1 Vacuum interrupterType VCP-W vacuum circuit breakers utilize vacuum interrupters forinterruption and switching functions. The vacuum interrupters usepetal type copper chrome contacts for superior dielectric strength,better performance characteristics, and lower chop current. Vacuuminterruption provides the advantages of enclosed interrupters,reduced size and weight, short interrupting time, long life, reducedmaintenance, and environmental compatibility.Arc interruption is simple and fast (Figure 19). In the closed posi-tion, current flows through the interrupter. When the contactsare opened, the arc is drawn between the contact surfaces. It ismoved rapidly around the slotted contact surfaces by a self-inducedmagnetic force, which prevents gross contact erosion as well asthe formation of hot spots on contact surfaces. The arc burns in anionized metal vapor which continually leaves the contact area andcondenses on the surrounding metal shield.Figure 19. Graphic representation of arc interruption.At current zero, the arc is extinguished and vapor production ceases.Very rapid dispersion, cooling, recombination, and deionization of themetal vapor plasma, together with the fast condensation of metalvapor products, cause the vacuum to be quickly restored. Hence, theopened contacts withstand the transient recovery voltage.5.2.2 Contact erosion indicationThe purpose of a contact erosion indicator is to monitor the erosionof the vacuum interrupter contacts, which is very minimal over timewith vacuum interrupters utilizing copper-chrome contact material. Ifcontact erosion reaches 1/8 in. (3.18 mm), the interrupter must bereplaced. A horizontal colored or machined contact erosion indicatormark is located on the moving stem of the interrupter (Figures 27and 28).In order to determine if the contacts have eroded to the extent thatthe interrupter must be replaced, observe the erosion mark placedon each moving stem from the rear of the breaker with the breakerclosed. The interrupter is satisfactory if the mark on the stem isvisible with the breaker closed. The entire interrupter assemblymust be replaced if the mark is no longer visible.5.2.3 Loading spring indicatorThe loading spring indicator is an additional method provided toindicate conditions within the interrupter. The indicator is used toindicate whether the contact springs are maintaining the adequatecontact pressure to keep the contacts closed. Severe contacterosion would result in an unacceptable indication from the indicator(Figure 29). Depending upon the structural design, a small mirrormay be required to inspect all three poles.Note that the actual configuration and/or appearance of the indica-tor can vary from one circuit breaker rating to another. The actualappearance of the indicator depends upon the color of the contactsprings in a specific circuit breaker. When making this inspection,first observe the color of the contact springs to determine how theindicator will appear. Figure 29 illustrates what the actual indicatorappearance will be, depending upon the color of the springs.5.2.4 Contact wipe and strokeContact wipe is the indication of (1) the force holding the vacuuminterrupter contacts closed and (2) the energy available to hammerthe contacts open with sufficient speed for interruption.Stroke is the gap between fixed and moving contacts of a vacuuminterrupter with the circuit breaker open.The circuit breaker mechanism provides a fixed amount of motionto the operating rods. The first portion of the motion is used toclose the contacts (i.e. stroke) and the remainder is used to furthercompress the pre-loaded wipe spring. This additional compression iscalled wipe. Wipe and stroke are thus related to each other. As thestroke increases due to the erosion of contacts, the wipe decreases.A great deal of effort has been spent in the design of all VCP-Wvacuum circuit breakers in order to eliminate the need for fieldadjustments of wipe or stroke.m CAUTIONTHERE IS NO PROVISION FOR IN-SERVICE ADJUSTMENTS OF CONTACTWIPE AND STROKE. ALL SUCH ADJUSTMENTS ARE FACTORY SET ANDSHOULD NOT BE ATTEMPTED IN THE FIELD.5.2.5 Phase barriersPhase barriers on all VCP-W circuit breakers are made of glass poly-ester. Table 21 gives the number and configuration of the barriersrequired for each circuit breaker rating.