Models 5E, 5F, 5G & 5H Electric Switch Machines: Single ... - Alstom

Theory of OperationWhen the switch machine is to operate to the left, positive control energy is applied tothe NWR wire and negative control energy to the WR wire. This causes contactor C2 tobe energized. When contactor C2 picks up, the snub contact opens. Contactor C2closes its front contact and, through the centering device, closes the back contact ofcontactor C1. This completes the motor circuit, and operating energy flows fromterminal 5, through the front contact of C2, the reverse field of the motor, the armature,the crank contact, the operating coil of the overload relay, and the back contact ofcontactor C1 to negative.As the switch machine unlocks, point-detector contacts 7D-2C close. The machinecontinues to operate to the left. When the machine completes its stroke, point-detectorcontacts 1C-8D open, de-energizing contactor C2 and opening the motor circuit. Thecontactor armatures return to their normally centered position and the snub contactcloses. The motor armature continues to rotate, generating a dynamic current that flowsfrom field coil through terminals 4 and 9, one-half of the snub rectifier, the snub resistorlead, the snub contact, terminals 12 and 7, the crank contact, terminal 6, the armature,terminal 1, and back to coil N.When the switch machine is to operate to the right, positive control energy is applied tothe WR wire and negative control energy to the NWR wire. This causes contactor C1 tobe energized. When contactor C1 picks up, the snub contact opens. Contactor C1closes its front contact and through the centering device closes the back contact ofcontactor C2 (point-detector contacts 7D-2C were closed and contacts 1C-8D wereopened during the operation of the machine to the left). This completes the motorcircuit, and operating energy flows through the motor in a direction to operate themachine to the right.As the machine completes its stroke, contacts 7D-2C open, de-energizing contactor C1and opening the motor circuit. The contactor armatures return to their normally centeredposition and the snub contact closes. Any overrun of the motor armature generates adynamic current that now flows from field coil through terminal 1, the armature, thecrank contact, terminals 7 and 12, the snub contact, the snub resistor lead, the otherhalf of the snub rectifier, terminals 8 and 3, and back to coil R.P1293, Rev. Jun/07 2–34 Alstom Signaling Inc.