Watch Standing

IC switchboard is usually the only one required to be

SYNCHRO OVERLOAD TRANSFORMERS

AND INDICATORS.-- Synchro overload transform-

manned. The IC Electrician on watch is responsible

ers and indicators are used in the ACO section of the

for recording hourly voltage, current, frequency, and

IC switchboard to alert operating personnel of a

ground readings of the various buses associated with

casualty or overload in the associated circuit.

the IC switchboard.

The transformers are wired in series with the

When checking for grounds, the watch stander

secondary connections of selected synchro torque

should compare the readings being taken with

instruments. Type B and C transformers are used for

previous readings. Unusual deviations should be

60-Hz and 400-Hz circuits, respectfully.

investigated and the cause determined. Low voltage

between any phase and ground, with high voltage

When the angular displacement of the synchro

between the other phases and ground, normally

receiver is in excess of 17 3 degrees from the position

indicates a ground on the phase with the low-voltage

of its associated transmitter, the indicator lamp

connected to the transformer will glow. This

reading.

displacement may be caused by an open or shorted

The watch stander is also responsible for

rotor circuit, an open or shorted stator circuit, or lack

investigating all blown fuse indications, synchro

of synchronism between transmitter and receiver

overload indications, and bus failure alarms.

caused by excessive bearing friction in the receiver.

When an overload indicator lamp is glowing, the

LOCAL IC SWITCHBOARDS

cause of the malfunction should be investigated

immediately and corrected as soon as possible. The

Local IC switchboards are type II, bulkhead-

switchboard operator can isolate the affected

mounted, front-service, enclosed units. Terminal

instrument from the circuit by operating the associated

boards and an ABT are mounted inside the switch-

ACO switch. If the circuit malfunction cannot be

board. Switches, fuse holders, and lamp holders are

determined, check the transformer setting. The

mounted on the door.

indication may be the result of the overload

The number of local IC switchboards installed on

transformer being set too low.

a ship depends on the type and class of that ship. As

stated earlier, local IC switchboards provide local

control of circuits vital to the operation of a space. The

NOTE

local IC switchboards that will be discussed in this

Operation of an ACO transfer switch

chapter are (1) engine room, (2) central control station,

normally causes the associated overload

and (3) steering gear room. There may be other local

indicator light to flash. This is due to a

IC switchboards installed aboard ships, depending on

momentary displacement between the

individual ship requirements.

transmitter and receiver. The flash is normal

and shows the system is operating properly.

Engine-room Local IC Switchboard

On some ships, a local IC switchboard is provided

POWER MONITORING INSTRUMENTS.--

in each engine room to energize local IC alarm,

The power monitoring instrumentation consists of

warning, and indicating systems.

voltmeters, ammeters, and frequency meters. There

are also phase selector switches for the voltmeters and

The engine-room switchboard operates on

the ammeters. These various meters are used to check

120-volt, 60-Hz, single- or 3-phase ac power, There

the voltage, current, and frequency of each input

are two sources of power available: normal and

power bus and the presence of grounds.

emergency. The nearest main IC switchboard provides

the normal power supply, The emergency power

Watch Standing

supply comes from a local emergency lighting circuit.

The emergency power supply provides the switch-

board with power if the normal supply is lost. The

When a ship is underway, the main IC switchboard

engine-room switchboard includes supply switches,

should be manned 24 hours a day. On ships where

there are two main IC switchboards, the forward main

an ABT device, and power available indicator lights.

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