Eaton VCP-W Instructions For Installation, Operation And Maintenance

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

IB131006EN Page 29Eff ect iv e 07/ 2017SECTION 5: DESCRIPTION ANDOPERATION5-1 INTRODUCTIONType VCP-W, VCPW-SE and VCPW-ND vacuum circuitbreakers are horizontal drawout designs for use in metal-clad switchgear compartments. Most ratings can bestacked two high in a vertical section resulting in aconsiderable savings of floor space.Vacuum interrupters are used with all circuit breakers toclose and open the primary circuit. All VCP-W circuitbreakers are operated by a front mounted spring typestored energy mechanism (Figure 3-3). The storedenergy mechanism is normally charged by an electricmotor, but can be charged manually with the manualmaintenance tool. Since the same basic, front accessiblemechanism is used for all VCP-W circuit breakers, aminimum investment in spare parts is required.The primary insulation used with Type VCP-W circuitbreakers is flame retardant and track resistant glasspolyester except for the Type VCPW-SE circuit breaker.The VCPW-SE special environment circuit breakerdesign utilizes cycloaliphatic epoxy for its primaryinsulation. “Fast On” type secondary control terminationsare used on Types VCP-W and VCPW-ND circuitbreakers, while the Type VCPW-SE circuit breakerutilizes ring type secondary control terminations.The rest of this section describes the overall operation ofthe VCP-W circuit breaker as well as the function andoperation of all major sub-assemblies and/or parts. Keepin mind that VCP-W will be used throughout the textwhen referring to any one of the three types of circuitbreakers, unless there is a specific difference betweenVCP-W, VCPW-SE and VCPW-ND.5-2 INTERRUPTER ASSEMBLYVacuum interrupters are mounted vertically andsupported from the fixed stem which is clamped to thetop conductor. The exclusive current transfer systemconsists of a series of plated, high-conductivity copperleaf conductors that are pressed on the movableinterrupter stem. This design provides a multipoint contactresulting in low electrical and thermal resistance. Utilizingthis non-sliding current transfer system between themovable stem and the breaker main conductoreliminates the need for maintenance (Figure 5-1).Multiple finger, floating type primary disconnectingcontacts at the ends of the top and bottom conductorsprovide a means for interfacing with the primaryconductors mounted in the switchgear (Figure 3-4).Figure 5-1 Typical VCP-W Rear View Showing VacuumInterrupters and Current Carrying SystemDirect acting insulated operating rods in conjunction withthe circuit breaker’s mechanism provide a fixed amount ofinterrupter movable stem motion. This motion is directlyrelated to the interrupter’s “Wipe” and “Stroke,” each ofwhich is discussed in detail later in this section.5-2.1 VACUUM INTERRUPTERType VCP-W Vacuum Circuit Breakers utilize vacuuminterrupters for interruption and switching functions. Thevacuum interrupters use petal type copper chromecontacts for superior dielectric strength, betterperformance characteristics, and lower chop current.Vacuum interruption provides the advantages of enclosedinterrupters, reduced size and weight, short interruptingtime, long life, reduced maintenance, and environmentalcompatibility.Arc interruption is simple and fast (Figure 5-2). In theclosed position, current flows through the interrupter.When the contacts are opened, the arc is drawn betweenthe contact surfaces. It is moved rapidly around theslotted contact surfaces by a self-induced magnetic force,which prevents gross contact erosion as well as theformation of hot spots on contact surfaces. The arc burnsin an ionized metal vapor which continually leaves the con-tact area and condenses the surrounding metal shield.