Power Distribution / General Electrical / Power Tools Flashcards
What do you use to discharge a capacitor?
A shorting probe across the terminals of the capacitor or the built in grounding bar.
What is the length rule for extension cords?
Only allowed to connect 2 25’ long cord and 1 100’ cord is permissible.
When working on electrical equipment you must have __________________ qualified person observing.
CPR
Primary power distribution voltage, phase and frequency is?
450V, 3 phase, 60 Hertz
Max voltage for a ship’s main switchboard should never exceed _________ volts?
462 volts
Shore power cables are rated for _______ amps?
400
Indicator RED lamp means?
Danger or emergency
Indicator GREEN lamp means?
Normal condition
Indicator WHITE lamp means?
Power available
Indicator BLUE lamp means?
Closed/Advisory
Indicator CLEAR lamp means?
Synchronizing or Ground detection
Indicator YELLOW lamp means?
Abnormal, but not requiring immediate attention.
What is a bus tie used for?
Used to connect or disconnect one bus, such as that in a switchboard, to another bus.
How do you minimize the loss resulting from eddy currents in a transformer?
Laminate the windings
What system are ACB breakers used on?
Ships service and emergency generators to the power distribution system, bus ties, shore connection circuits.
What is an NLB breaker essentially?
An off/on switch
They have no automatic tripping device
What does “trip free” mean?
A breaker that will remain open, even if the mechanism is held in the closed position.
Grounds can’t be detected through what?
A transformer
Power factor of 100% means the circuit is purely ________?
Resistive
UPS prevent ___________ outs.
Brown
A ___________ is a device without moving parts that transfers energy from one circuit to another by electromagnetic induction.
Transformer
Permanent magnet movement is known as the ___________ movement.
D’Arsonval
Shore power cable can be spliced, true of false?
True
The distance between cable supports should not exceed how many inches?
32”
What amperage does a GFCI trip?
4mA or higher
What is the unit of measure for Capacity?
Fared
The 4th band of a resistor indicates?
Tolerance
In a step up transformer voltage ________________ and current _______________?
Increase and decrease
Cathodic protection system prevents ________ and ________ on the ships hull.
Corrosion and rusting
The efficiency of most transformers are ___% to ___%?
97-99
All deep fat fryers must be what type of circuit breaker?
Shunt trip
Which circuit breaker is used to protect single load circuits and all feeder circuits coming from a load center distribution panel?
AQB
Which type of transformer receives electrical energy at one voltage and delivers it at the same voltage?
Isolation
For shipboard the shore tie cable must be? List all the factors!!!
3 conductor Flexible Unshielded 600 volt THOF-400 or 500
What type of transformer isolates instruments from line potential and produces in the secondary a definite fraction of the primary current thereby making it possible to measure large currents with a five ampere ammeter?
Current transformer
A rheostat is basically what?
A variable resistor
Resistive wire wrapped around a cylindrical core, with a wiper moving over the surface of the wound wire core to vary the resistance within the circuit, describes a ________?
Rheostat
What component is defined as the 3 terminal variable resistor where the center connection is manipulable?
Potentiometer
Which meters are usually the only instruments provided for DC distribution systems?
Voltmeters and ammeters
A ____________ is a three terminal variable resistor where the center connection is manipulable?
Potentiometer
What voltage is class 0 rubber glove?
1000 volts
What voltage is class 1 rubber glove?
7500
What voltage is class 2 rubber glove?
17,500
What voltage is class 3 rubber glove?
26,500
Which type of breaker can be both manually ad electrically operated?
ACB
Number of strands that can be broken or nicked
Less then 7 7-15 16-18 19-25 26-36 37-40 41 or more
0 1 2 3 4 5 6
From any conductor in a power tool to ground of any part of the casing of the tool you should read?
Greater then 1 meg ohm
What resistance should you read between the case and the ground/hull of a ship?
1 ohm or less
What do the dots on a electrical drawing of a transformer represent?
They tell which way the phase is going throughout the coil. It lets you know how current is following at a glimpse of looking.
Resistor color code, do it up!
(0) Black
(1) Brown
(2) Red
(3) Orange
(4) Yellow
(5) Green
(6) Blue
(7) Violet
(8) Grey
(9) White
Gold is 5%
Silver is 10%
What 2 pronged piece of equipment is allowed to be plugged into a receptacle that reads “warning: insert three prong grounded plugs only”
Double insulted tools
How long does a ground on a 3 plug cord have to last?
The life time of the tool/piece of equipment.
How often is should a switchboard be de-energized, throughly inspected, and cleaned?
Yearly
What is the maximum splices in a cable run?
2
What does the bus transfer system provide?
2 sources of power to equipment that is vital to the ship.
What precaution must be taken when testing bus transfer equipment?
Ensure any vital or sensitive loads are on backup
Circuit breakers provide the power distribution system with what 3 functions?
Normal switching operation, circuit protection, and circuit isolation.
Which circuit breaker is used to protect single load circuits.
AQB
Which type of transformer receives electrical energy at one voltage and delivers it at the same voltage?
Isolation
What would cause failure of the overcurrent device to trip the switchboard circuit breaker?
Insufficient trip travel
What meters are usually the only instruments provided for DC distribution systems?
Voltmeters and ammeters
Voltmeters and potential coils of watt meters are connected?
Either across the voltage to be measured or the secondary of a potential transformer
When testing portable tools you must test them with the switch in the?
On and off position
Which type of switch requires the physical contact of an object with the switches activator to make the contacts change state?
Limit switch
For cable and conductor termination within an enclosure, how many conductors can be attached per lug?
1
Coaxial connectors exposed to weather elements , shall be weatherproofed within _____ hours after assembly?
24
What do the 4 lines mean on a resistor?
1 and 2 determine number
3 is the amount of 0’s (multiplier)
4 is the tolerance
How many strands of the conductor can be broken or nicked in the following?
7
7-15
16-18
19-25
0
1
2
3
What % over the load should fuses be on motors?
250-400%
What are the 3 types of transformers?
Air core
Iron core
Soft iron
Max voltage for class 4 gloves?
36,000
No more then _____ row(s) of cables should be installed on a single hanger?
1
A circuit breaker relay magnet that chatters is caused by what?
Rusty sealing surface
The most common cause of controller contacts welding together is what?
Low voltage
The height of a kick pipe including the stuffing tube is ___” minimum and ____” max?
9
18
___________ is the measure of electron flow?
Current
______ type controllers must be manually restarted after electrical power has been restored?
LVP
______ type controllers will automatically started after electrical power has been restored?
LVR
Frequent welding of contacts can be avoided by using ________ contacts.
Silver
the primary purpose of PMS of electrical cable is to preserve what?
Insulation resistance
Arc chutes should be cleaned with a ______ and scraped with a ______?
Cloth and file
Transformers are rated by _____?
KVA
What is a varistor used for?
Protect circuits from voltage surges
The half moon shape on a capacitor tells you what?
The positive side
What designates the mark of the primary terminals and the secondary terminals that have the same instantaneous polarity?
A dot
Max tiers of a bulkhead wire run?
2
3 with NAVSEA approval in close quarters
Cable banding is how wide?
5/8”
How much slack is allowed in a cable run from hanger to hanger?
1”
What are the 3 spacing distances between wire hangers?
12, 21, 32
Max tiers for cable runways in the overhead?
5
Shore tie insulation is tested on what voltage of a megger?
500 volts
If you have 2 shore ties, they must be the same length why?
For voltage unbalance
What is another word for power loss in the run of a cable?
Attenuation
What does the AQB-LF250 breaker have that the AQB breaker does not?
Fuse
What is the description of an ALB breaker?
Low voltage
Automatic tripping
The NQB-A250 breaker is similar to what other breaker?
AQB-A250
But…
It has no automatic tripping device!
What breaker is the NLB breaker similar to and what is the description of it?
Same as the ALB breakers
But…
They have no automatic tripping device!
It’s basically an on/off switch!
What 2 breakers are considered an on/off switch due to manual operation only?
NQB and NLB
What substances should you never clean electrical equipment with?
Alcohol Gasoline Benzene Ether Carbon tetrachloride Emery cloth Steel wool
What substances are SAFE to use to clean electrical components?
Water based solvents
Non-volatile substances
When not possible to clean with these then you can use…
Inhibited methyl chloroform, in a well ventilated space
What are the classifications of cable types?
Special purpose
Nonflexing service
Repeated flexing service
What is the purpose of aluminum or steel covering of armored cable?
To give physical protection to the cable sheath during installation.
What is the purpose of using nonflexing cables?
Permanent installation
Repeating flexing service cable is designed to be used on what type of equipment?
Portable tools
Repeated flexing cable is categorized by what means?
Number of conductors in the cable
If you see the symbol HOF on a cable designation, what does this mean?
Heat and oil resistant, and its flexible
A cable is listed in the cable comparison guide has a 7 at the end of the cable designation, what does this mean?
The # of conductor pairs and the circular mils of the conductor only
Or
The number of conductors, the number of conductor pairs, and the circular mils.
It depends on the type of cable…
LSDHOF-400
What does the D mean and what does the 400 mean?
2 conductors
And
Conductor expressed in thousands of circular mils
A cable has been constructed to add protection against fire, what type of cable does this explain?
Circuit integrity
When installing a replacement cable for a particular install ion, you must know all except?
The number of bends in the cable
Why do you want to keep cable runs as short as possible?
To keep attenuation to a minimum
What letter indication do the following mean in reference to cable markings?
EL N L CP EP P CPS G PP
Emergency lighting Navigation lighting Ship lighting Casualty power Emergency power Ship service power Cathodic protection Fire control Propulsion power
What manual would you find the exact way of installing cable?
Cable comparison guide
What type of meter would you use to test insulation resistance?
Megger
Neutral polarity in a conductor is identified by what color?
White
The marking system for power and lighting cables is shown in what order?
Source
Voltage
Service
Let’s break down these cable markings….
X-XX-XX)-24-A(2
(X-XX-XX)-4P-B(1)
Deck
Frame
Port or starboard
If less then 100 volts, it will display actual voltage, so 24 volts
If its just a single digit its the range in hundreds, so 4 would be 400-500.
Letters represent what breaker in order
Last number represents section of a power main with more then one section.
What is a way to keep your cable runs neat in appearance?
Lace them together
What is the purpose of insulation on cables?
Isolates current carrying conductors of other circuits or equipment
And
Insulates points of unequal potential from one another
Electrical insulting materials are classified according to what characteristic?
Their temperature index
The most common insulations for cable are classes….
A
B
C
O
Name them
Cotton, paper and similar organic materials that are impregnated or immersed in liquid dielectric
Mica, asbestos, fiberglass etc…
Glass, quartz, tics, etc…
Paper, cotton, thats not impregnated or immersed
What is selective tripping?
Isolates faulty circuits with interrupting other associated circuits
When testing a ground receptacle, what is the maximum acceptable resistance from the ground connection to the hull?
Less then 1 ohm
At what interval should the connections of new electric wiring be tested?
Before being used for the first time!
Don’t confuse this with when do you PMS portable tools or when do you inspect a tool when you get issued it.
What NSTM would you refer to for electrical matting on decks?
NSTM 634
What is the distance for electrical matting from any electrical hazard?
3 feet
How many amps are lethal?
.1 to .2 amps
What is the function of the switchboard bus ties?
To permit switchboards to be cross connected and to allow paralleling of generators.
