Siemens 38-3AH3 38 kV Instruction Manual

Contents

Vacuum interrupter/operatorThe spring-dump cam raises thespring-dump interlock uponinsertion of the circuit breaker intothe compartment, or uponwithdrawal from the compartment.The interlock is raised at about thetime the front wheels pass over thecubicle sill.It allows the spring-dump interlockto be in the reset (lowest) position atall other times.The operation of the spring-dumpinterlock may be seen in Figure 34:Interlock mechanisms on the type38-3AH3 vacuum circuit breaker onpage 37. As the interlock rises (5.0),it causes the guided tube (4.0) torise and enter the operating-mechanism enclosure.Figure 35: CLOSED circuit-breakerinterlock mechanism in stored-energy mechanism shows theoperating mechanism detailcomponents that establish a spring-dump condition as the tube rises.The rising tube raises a leverattached to the base of theoperating-mechanism enclosure.This lever raises the trip-freepushrod, that elevates the closing-spring release cam. The closing-spring release cam moves theclosing-spring latch, that causes theclosing springs to discharge.However, the trip-free interlock israised, so that the operatingmechanism is held trip-free (refer to"Trip-free interlock" on page 33).Thus, the energy in the closingsprings is released (spring-dump),without movement of the jack shaftor the vacuum-interrupter contacts.D. Trip-free interlock position -mechanical interlockIn order to prevent the motor-charging circuit from "making andbreaking" as the circuit breaker andcubicle secondary disconnects makeor break physical contact, anelectrical switch is provided. Thisswitch is mounted in the line ofaction taken by the trip-freeinterlock plunger that follows theracking-mechanism cam and iselevated at all times while the circuitbreaker is in the drawoutcompartment except when in theTEST or CONNECT positions.A striker plate, integral with the trip-free interlock plunger, engages andoperates (opens) the switch whenthe plunger is in an elevated positionblocking spring-charging motoroperation. The switch is closed whenthe circuit breaker occupies the TESTor CONNECT position, allowing thecharging motor to operateautomatically.39