electricity for refrigeration heating and air conditioning
what characteristics would apply to copper being used as a good conductor
good mechanical strength, ability to resist corrosion, and easily joined together
what is the disadvantage of using aluminum wire?
what are four factors that should be considered in sizing circuit conductors
voltage drop, insulation type, enclosure, and safety
how would you determine the voltage drop in a circuit
if there is a maximum voltage drop at the branch of the circuit of 3% but also the allowable voltage drop of most manufactures is 10%
what is a disconnect switch
it is a 2 or 3 pole switch mounted in an enclosure
the most popular conductor used in the industry is?
what is the difference between a fusible disconnect switch and a non fusible disconnect switch
fusible disconnect switch should be used with the proper fuse sizes while non fusible disconnect switch if means of protection for the wire or equipment is needed
application determines what?
the type of insulation surrounding the conductor
how many hot legs would a three pole breaker supply to an appliance
three hot legs and makes up a three phase circuit at the supply voltage
national electrical code determines what
the size and installation of an electrical circuit
what is the purpose of a disconnect switch
to disconnect power from the equipment
what is the difference between a fusible load center and a breaker load center? which is primarily used in the industry today
fusible load centers are older and you can find them when installing an air conditioning system to a older house while breaker load centers are in buildings and other structures today, in the industry breaker load centers are most common to find
what is a circuit breaker?
disconnecting power from the circuit
how can a faulty circuit breaker be detected?
either they cannot be reset or they open the circuit on a lower amperage than the rating
how are circuit breakers attached to the main lugs of an electrical panel
either with screws or with clips
what is a distribution center and what is its primary purpose?
distribution centers are designed to distribute the electrical supply to several places in large structures their use in largely confined to commercial and industrial applications
a distribution center is used in?
commercial and industrial
what is true about the american wire gauge?
there largest wire is No. 4/0 and wires larger than 4/0 are sized in circular mils
true or false: fusible load centers are usually installed in residences today
what connects the breaker to the source of power in a breaker panel
the main lugs
what would you do in a situation where there is no spare opening in a breaker panel for the installation of equipment
a breaker with two circuits can replace a standard one circuit breaker
true or false: in all areas of the united states, air conditioning technicians can install the conductor from the distribution panel to the equipment
what is the purpose of a main breaker
it is a supply system that divides its power feed to other breakers it is also the main power to all equipment
what is magnetism
the physical phenomenon that includes the attraction of object for iron and is exhibited by a permanent magnet or an electric current
the strength that a motor produces by turning
the area in which a magnetic force operates, around an electric wire, and an electric motor
true or false: a permanent magnet is a piece of material that has been magnetized and can hold its magnetic strength for a reasonable length of time
how is an electromagnet produced?
it is produced by energy
what produces the best electromagnet?
unlike poles of a magnet ________ each other while the like poles____________ each other
what part does polarity play in the operation of an electric motor?
it causes the rotor to move
what part of a motor produces an inductive magnetic field within itself to facilitate the rotating motor?
squirrel cage motor
what part does the frequency of an alternating current play in the operation of an electric motor
it directs the flow of current to the motor
what are the five types of single phase motors used in the industry
shaded pole, split phase, permanent split capacitor capacitor start capacitor run and capacitor start, electronically communicated
list the motors starting torque from lowest to highest
shaded pole, split phase, capacitor start, three phase
what is the common use of a shaded pole motor?
how does a shaded pole operate?
a current runs in the windings, the poles create a magnetic field and start rotating to give it a sufficient torque, and when it is at full speed it is negligible
how can a shaded poole be reversed?
the sat or must be reversed to change position and you have to disassemble the motor
what determines the rotation of a shaded pole motor
location of shaded pole
what enables a split phase motor to develop enough torque to begin rotation
it uses two windings to displace the phase and create the needed displacement between the run and start windings to produce rotation
centrifugal switch does what?
removes the starting winding from the electrical circuit of an open type split phase motor once it reaches 75% of its operating speed
what are the three probable areas of trouble in a split phase motor?
nearings, windings and centrifugal switch
what is the unit of measurement for the strength of a capacitor?
what is the purpose of a capacitor?
to boost starting torque and increase running efficiency
what is the difference between a running and a starting capacitor?
a starting capacitor is built in a small case with a dielectric or a nonconductor of electric current while a running capacitor displaces heat is in a larger case but it is small
explain the operation of a permanent split capacitor motor
it is used on compressors where the refrigerant equalizes on the off cycle on direct fan motors it is a simple design and has a moderate starting torque
how are a PSC motor and a capacitor start capacitor run motor similar
both use a running capacitor
what are the similarities between an open type split phase motor and a capacitor start motor
both have a capacitor
what is an advantage in using a three phase motor
True or False: all starting apparatuses are mounted externally to the hermetic compressor shell
What is the process in trouble shooting any electric motor
open up the motor checking the windings bar rings speed of winding and motor