Coast Guard Ema Power Distribution Systems

Front 1

Loads that can be immediately secured without adversely affecting ship operations, survivability, or life. Identified by a white marker or placard.

Back 1

Non vital (non essential)

Front 2

Loads important to the ship but can be shut down or switched to alternate plant in order to prevent total loss of ships electrical power. Identified by a yellow marker or placard.

Back 2

Semi-vital (Semi-essential)

Front 3

Loads that affect survivability of ship or life. Power to these loads is not intentionally interrupted. Identified by a red marker or placard.

Back 3

vital (essential)

Front 4

The primary power distribution voltage, phase, and frequency used on U.S. Coast Guard cutters is -----volts, -----phase, -----herts.

Back 4

450 Volts
3 phase
60 hertz

Front 5

The secondary power distribution voltage, phase, and frequency used on Coast Guard cutters is -----volts, -----phase, -----herts.

Back 5

120 volts
3 phase
60 hertz

Front 6

Power system bus voltages are rated 450V and 120V, while nominal voltage ratings for utilization equipment are ----- and -----.

Back 6

440V and 115V

(Voltage at the utilization equipment terminals can vary because of changing loads and their effect on generator voltage and distribution cable voltage drops.

Front 7

The 440V and 115V, 60-Hz power supplied to equipment by the ships power and lighting distribution systems is designated type ---- power.

Back 7

1

Front 8

The 440V and 115V 400-Hz Power supplied to equipment by 400-Hz motor-gen sets or solid-state converters is designated type ----- or type ----- power.

Back 8

type 2 or type 3
The tolerances for type 3 power are much tighter than the tolerances for type 2 power.

Front 9

Grounded three phase, four wire power is provided for ----- and -----.
(Special power types aboard ship)

Back 9

Avionics shops and aircraft servicing

Front 10

-----, 115/200V, 60Hz power for certain avionics shops where equipment requires a grounded three phase power source.

(Special power types)

Back 10

Type 1

Front 11

-----, 115/200V, 400Hz power for avionics shops.

(Special power types)

Back 11

Type 3

Front 12

Aircraft electric power characteristics include steady state voltage limits of ----- to ----- measured at the aircraft external power receptacle.

(Special Power types)

Back 12

113V to 118V

Front 13

The 115/200V at the user equipment terminals of a grounded four-wire system is nominally -----V, measured from a phase conductor to neutral, and -----V measured between any two phases.

Back 13

nominally 115V

200V measured between any two phases.

Front 14

Voltage at the utilization equipment terminals can vary because of changing ----- and their effect on generator voltage and distribution cable voltage drops.

Back 14

Loads

Front 15

----- frequency is the designated frequency of the power system.

Back 15

Nominal Frequency

Front 16

The ----- on Coast Guard cutters is A B C, that is, the maximum positive voltages on three phases are reached in the order of A,B,C.

Back 16

Phase Sequence

Front 17

Phase sequence determines the ----- of three phase motors.

Back 17

Direction of rotation

Front 18

For a delta connected system, maximum positive voltages on the three phases are reached in the order of .....

Back 18

AB, then BC, then CA

Front 19

What is the color coding for 3 conductor and 4 conductor three phase AC systems.

Back 19

3 conductor: A - Black
B - White
C - Red

4 conductor: A - Black
B - White
C - Red
neutral - green

Front 20

In a ------ system, each load is connected to only one switchboard at any one time.

Back 20

radial system

Front 21

The ship service generator and the distribution switchboards are interconnected by -----, so that any switchboard can be connected to feed power from the generator to one or more switchboards.

Back 21

Bus ties

(connect two or more switchboards so that the generator can be operated in parallel)

Front 22

An ----- shows the amount of current flow supplied to the switchboard from the generator.

Back 22

Ammeter
(Normally connected to measure generator output current via a current transformer.)

Front 23

For high current measurement, the ----- transformer transforms high current to lower currents.

(Primary winding has only a few turns or may be a part of the bus bar.) (High voltage present in the primary)

Back 23

Current Transformer

(Secondary normally has 100 turns or more.)

Front 24

Caution
Never open the ----- of a current transformer wen the primary has current flowing through it. Doing so may cause: danger to personnel, or equipment damage

Back 24

Secondary

Front 25

A ----- shows the generator terminal voltage. In some installations, they also show phase voltage to ground. It is connected to the generator output via potential transformer.

Back 25

Voltmeter

Front 26

For high voltage measurement, the ----- transformer transforms high voltages to lower voltages.

Back 26

Potential transformer

Front 27

The stepped-down voltage of a potential transformer is ----- volts (usually) to be measurable by a meter.

Back 27

120 volts

Front 28

Potential transformers match the ----- of the connected meter.
(Insulation must be strong enough to resist the high voltage present on the primary winding.)

Back 28

impedance

Front 29

Caution
When working on or near potential transformers never ----- the secondary when the primary has current flowing through or the following can result: danger to personnel, equipment damage

Back 29

short

Front 30

A ----- shows the amount of power consumed by the loads connected to the switchboard.

Back 30

Wattmeter

Front 31

A ----- meter shows the operating frequency of the generator.

Back 31

Frequency Meter

Front 32

A ----- shows the phase relationship of an oncoming generator compared to the frequency of the bus.

Back 32

Synchroscope and synchronizing lamps

Front 33

When synchronizing lamps are lit, the generator terminal voltage, and the bus voltage are -----.

When the lamps are dark, gen and bus are -----.

Back 33

Lit - out of phase

dark - in phase

Front 34

A ----- meter shows the efficiency of the entire power distribution system.

Back 34

Power factor meter

Front 35

The power supplied in AC circuits is made up of:
-Useful (resistive) power, dissipated by -----.

- ----- stored by the distribution system's reactive devices. This power circulates in the circuit, serving no useful purpose.

Back 35

loads

Reactive Power

Front 36

The ratio of useful power to reactive power is the -----.

Back 36

Power factor

Front 37

Indicator light color designation (except for special applications in dark adapted spaces)

(Indicators with red lenses and stencil-type marker discs are used in dark spaces requiring visual adaptation by personnel.

Back 37

- Red - danger or emergency condition requiring immediate attention or corrective action.

- Green - normal condition

- White - power available or power on

- Blue - closed, advisory

Clear (not etched) - synchronizing or ground detector lights

- Yellow - abnormal, but not requiring immediate attention

Front 38

----- are installed on most large and some medium sized ships to supply groups of loads and large auxiliaries located in the same general area.

Back 38

Load Centers

Front 39

All distribution panels are provided with cabinet -----, that contain the following info in the order listed.

1- the name of the space, apparatus, or circuits served
2- the service (power, lighting, electronics, and so forth) and basic location number.
3- the supply feeder number.

Back 39

information plates

Front 40

----- supply groups of loads that are located in close proximity to each other, or that operate together to perform a function.

Back 40

Power distribution panels
(Provide for control of selected portions of the distribution system.)

Front 41

A reliable supply of power is maintained for vital electrical loads. This is done by supplying ----- sources o power to these loads, providing load shedding of non vital loads to avoid overloading the remaining generating capacity, and supplying redundant equipment from separate power sources and distribution circuits.

Back 41

Two or more

Front 42

----- is used to select either the normal or alternate feeder, or to obtain power from the emergency distribution system (if an emergency feeder is provided)

Back 42

Bus transfer equipment

Front 43

----- units are often used instead of ABT's for many applications where a bus transfer device is required for loads that must be manually restarted after loss of power.

Back 43

Manual Bus Transfer
(MBTs may be used to switch from normal to alternate or emergency power for those loads that draw a large starting current or that must meet some condition before energizing)

Front 44

----- Units transfer to the alternate feeder automatically whenever the normal feeder voltage drops to 60 to 70 percent of normal voltage for more than .3 to .5 seconds.

(Transfer back to normal feeder when its voltage recovers to 85 to 95 percent of normal voltage)

Back 44

Automatic Bus Transfer

(Used to provide two sources of power to those loads that MUST be re-energized as soon as possible)

Front 45

ABT switches on lighting systems are either the ----- type or instantaneous.

Back 45

time delay

Front 46

The ----- ABT switch operates on 120V, 60Hz circuits and is usually used to handle small lighting circuits.

Back 46

Model A-2

Front 47

The A-2 ABT is designed to shift automatically from normal to alternate or emergency source of power when the source voltage drops to the dropout range (-----) across any two of the three phases.

(An intentional time delay of .3 to .5 seconds in both the transfer and retransfer operations is built in to prevent unnecessary transfer of power during line voltage surges and very short duration losses of power)

Back 47

81 to 69 volts
Upon restoration (98-109 volts) the unit will transfer back to normal.

Front 48

When testing any ABT, make sure any vital or sensitive loads fed from the ABT are -----.

Back 48

Isolated

Therefore, before beginning testing an ABT, you must notify all personnel concerned of the power supply system interruptions.

Front 49

Most ships have 450V and 120V, 400Hz power systems for supplying -----, -----, -----.

Back 49

Weapons systems, electronic equipment, and for servicing aircraft.

Front 50

----- reduces the amount of cabling and watertight penetrations required, and simplifies damage control and maintenance.

Back 50

Zone Distribution

Front 51

The AC power distribution system aboard ship is made up of.....

Back 51

-AC power plant
-Switchboards that distribute the power
-The equipment that consumes the power

Front 52

----- - includes at least one emergency generator supplies limited power to ships control and vital equipment

Back 52

Emergency power system

Front 53

----- - supplies power to only vital equipment required for minimal ship operation.

Back 53

Casualty power system

Front 54

----- - generators, switchboard, distribution panels, transformers, ships service wiring distribution to which supply power to all shipboard equipment.

Back 54

Ship Service Distribution System