The motor and firing cutout camstack assembly, like the train synchros, is driven by the synchro gearing in the bottom of the train synchro control box. The camstack assembly consists of a stack of 10 cams and 10 cam-actuated microswitches. As the gun mount moves in train, the camstack rotates in a 1-to-1 ratio matching train movement. The cams are cut during installation to conform to the structure of the ship at the gun mount location.

The cams are numbered 1 through 10 from top to bottom. The No. 1 cam is a spare. The No. 2 cam is cut to indicate the train stow position. When the gun mount is at the stow position, the No. 2 cam deactuates its microswitch, which allows the normally closed contacts to close and light the TRAIN-IN STOW POSITION lamp at the GCP.

Four of the remaining cams deactuate their associated microswitches (opening the contacts) to disable the firing circuit as the gun mount trains into nonfiring zones. Two other cams are spare nonpointing zone cams. The remaining two cams deactuate their associated microswitches (opening the contacts) to disable the train motor circuits. With the motor circuits disabled, the brake is set. This action prevents the barrel from entering the nonpointing zone if the electronic nonpointing zone system fails. When the motor circuits are disabled, the barrel must be manually cranked out of the nonpointing zone.

Dials and Dial-illuminating Lamps

The train synchro control box contains five dials, driven by the synchro gearing. The dials indicate the train position of the gun mount. One of the dials is on the tilt-angle potentiometer; another is on the tilt-angle correction CX. These dials are used to adjust the tilt-angle correction between the gun mount and the FCS reference (not used with the Mk 92 FCS). The remaining three dials are graduated to provide coarse, fine, and superfine indications of the train position.

The coarse position dial is graduated in degrees from 0 to 360. This dial makes one revolution with each revolution of the gun mount. The fine position dial is graduated in 5-minute increments between 0 and 10 degrees. This dial makes 36 revolutions with each revolution of the gun mount. The superfine position dial is graduated in l-minute increments between 0 and 120 minutes. This dial makes 180 revolutions with each revolution of the gun mount.

The train synchro control box contains two dial-illuminating lamps. With the protective cover of the synchro control box removed, the lamps permit the synchro dials to be read. The lamps are on when the servo system power is on.

POWER SUPPLY

The train and elevation systems use a common power supply, consisting of three transformers located at the GCP. The transformers supply the power required to drive the train and elevation motors. The transformers also supply power to the train and elevation motor control systems. The power supply transformers (refer to fig. 5-32 and table 5-6) are the main transformer (T1), the signal-ramp (sawtooth) transformer (T2), and the electronic supply transformer (1J1-T1) (not shown).

Main Transformer T1

The main transformer (T1) is located at the GCP and supplies power to the train and elevation motors. The ships supply provides 440 VAC three-phase power 60 Hz for Mod 0 or 400 Hz for Mod 1) to T1. Transformer T1 then provides six outputs of 170 VAC power. The six outputs provide a common power supply to the train and elevation motors.

Signal Ramp (Sawtooth) Transformer T2

The signal-ramp (sawtooth) transformer (T2) supplies power to the phase-consent and signal-ramp circuits. The ships supply provides 440 VAC three-phase power 60 Hz for Mod 0 or 400 Hz (for Mod 1) to T2. Transformer T2 then provides 50 VAC six-phase power to the phase-consent and signal-ramp circuits.

Electronic Supply Transformer 1J1-T1

The electronic supply transformer (1J1-T1) is located in the power supply module 1J1 of the GCP. Ships supply provides 115 VAC 400 Hz single-phase power to 1J1-T1.

MOTOR CONTROL SYSTEM

The motor control system regulates the polarity and amplitude of the current supplied to the train and elevation motors. This action controls the direction and speed of motor rotation. The motor control system is mostly electronic and consists of the following components and circuits at the GCP: the: silicon-controlled rectifiers (SCRs), the phase-consent and signal-ramp circuits, the demodulator circuits, the error amplifier circuits, the tachometer circuits, and the motor current-limiter circuits.

Silicon-Controlled Rectifiers (SCRs)

The SCRs (fig. 5-58) are solid-state electronic devices that act both as switches and as rectifiers. The train and elevation systems each use 12 SCRs to control the speed and direction of the drive motors. The 12 train SCRs are located on modules 1J6 and 1J8 (refer to fig. 5-31 and table 5-5). A pair of SCRs control each of the six 170 VAC voltages. These voltages are supplied to the SCRs by the main transformer T1.

One SCR in each pair conducts current for clockwise rotation; the other conducts current for counterclockwise rotation. The polarity of the error signal determines which SCR in each pair conducts. The magnitude of the error signal determines the amount of current flow through the SCR. The current controls the speed of the motors.

The conduction of the SCR depends on a positive potential being present on its control gate. It also depends on a forward bias between its anode and cathode. Once turned on, the SCR continues to conduct until the potential between the anode and cathode is either interrupted or inverted.

Figure 5-58.-Silicon-control1ed rectifier (SCR).