Electrical Installations Flashcards
What was the driving force for developing the low smoke family of cables?
The navy needed a new cable that would give off less toxic fumes and smoke during a fire
Which of the following are classifications of cable types
Special purpose
Non flexing
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 non flexing cable
To use with permanent installations
Flexing service cable designed for use aboard ship is commonly referred to as being portable because
It is principally used as leads to portable electric equipment
Repeated flexing, general use-cable is categorized by what means?
The number of conductors in the cable
If you see the symbol HOF on a cable designation you know the cable is of what type
Heat and oil resistant, flexible
If you need to find a comprehensive listing of the requirements for installing cables aboard Navy ships, you should refer to what publication
General specifications for ships of the U.S. Navy, NAVSEA S9AAO-AA-SPN-010
A cable has been constructed so that it provides added protection, allowing it to function for a longer period under fire conditions. What term describes this cable?
Circuit integrity
What information is on the thin marker tape present on most cables and cords under the binder or jacket
Name and location of the manufacturer
The year the cord or cable was made
The MILSPEC number of the cord or cable
When selecting a replacement cable for a particular installation, you must know all EXCEPT which of the following factors?
The number of bends in the cable
Before choosing the size of the cable to use in a circuit installation, what information is necessary for you to know?
The total connected load current, the demand factor, and the allowable voltage drop
Which if any of the following is the reason for keeping cable runs as short as possible?
To keep attenuation to a minimum
What letters would be used to designate an emergency lighting circuit on a cable supplying 115 volts ac to a circuit with a load of 120 watts
EL
You are installing new cables, you should measure the bend radius at what point on the cable?
On the innermost portion of the cable
In what publication will you find the exact method to use when installing cables
Electronics installation and maintenance handbook (EIMB)
What action should you take before you clamp a solder-type terminal to a conductor
Twist the strands tightly and solder them only
A cable has been newly installed. What type of meter should you use to test the insulation resistance?
A megger
Neutral polarity in a conductor is identified by what color?
White
The marking system for power and lighting cables is shown in what sequence?
Source, voltage, service
A cable marked as (1-120-2)-24-C(2) indicates that the circuit is supplying a maximum voltage of ?
24V
A circuit marking if (4-168-1)-4P-A(1) indicates that the circuit is supplying (a) what voltage and (b) what type of power
450v
Ships service
If you want cable to present a neat appearance and to be traced easily in equipment, you should take what action
Lace them together
What is the primary purpose of cable maintenance
To preserve the insulation resistance
Which of the following purposes is/are served by insulation on electric cables and equipment?
Isolating current-carrying conductors and conductive structural parts of other circuits or equipment
Insulating points of unequal potential from one another
Electrical insulating materials are classified according to what characteristic
Their temperature index
Electrical insulating materials are classified according to what characteristic?
Their temperature index
What type of insulation is impregnated cotton
Class A
What class of insulation is quartz
Class C
What class of insulation is paper
Class O
What class of insulation is asbestos
Class B
Shipboard lighting transformers in a 60-hertz circuit are constructed using what class insulation?
Class B
What is the limiting temperature of a piece of equipment with class N insulation?
200degrees C
You would use a monograph when taking what measurement
The resistance/foot of a cable
If a cable has been energized for 6 hours, what temperature should the cable be assumed to be for purposes of heating resistance?
104F
What is the size and designation for casualty power cables on ac power systems
LSTHOF-42
Casualty power cable leads are color coded for identification. What are the proper colors for a,b, and c phases respectively
Black
White
Red
To provide or install shore power to a ship requires which of the following equipment?
Shore power station and receptacle
Connecting cable
Cable plug
The shore-power system is designed to provide enough power for all equipment normally energized while at sea
False
You are connecting casualty power cables in a dark compartment. What conductor feature is identified by three separate servings of twine or o-rings
Phase C
What type of cable is used to connect fixed terminals that penetrate decks and bulkheads
LSTSGU-75
Shore power is supplied to the ship through the use of (a) what specific length of (b) what type of cable?
150ft
THOF-400
You are testing the phase sequence of a shore connection. What is indicated by a clockwise rotation of the phase sequence indicator?
Correct phase sequence
Kick pipes that penetrate wooden decks should be made from what material?
Aluminum
Limit switches are installed so they are connected in what configuration with (a) the master switch and (b) the voltage supply circuit?
Series
Series
What is a pilot device?
A small device that controls a large device
A thermal overload relay is adjusted to trip at a predetermined value. What action can you take to vary the tripping current
Move the relay heater coil
What type of protection is provided by reverse-power relays?
They protect the generators from damage by motoring prime movers
When two or more dc generators are connected in parallel, what device disconnects a generator from the line if the generator starts drawing power from the line?
A reverse-current relay
What is the closing sequence of the contacts in an ACB circuit breaker
Arcing contacts close; then the main contacts close
The instantaneous trip setting of the AQB-A250 circuit breaker is adjusted by using what components?
Adjusting wheels
Which of the following circuit breakers must be manually operated to interrupt current flow
Type NQB
type NLB
Selective tripping is useful aboard ship for what reason?
It isolates faulty circuits without interrupting other associated circuits
When testing a grounded receptacle, what is the max acceptable resistance from the ground connection to the ships hull
1.0 ohms
