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know the parts that make up the primary circuit
main power switch, circuit breaker, autotransformer, exposure timer, primary side of step up transformer
know the parts that make up the secondary circuit
secondary side of step up transformer milliampere meter, rectifier
know the parts of the filament circuit
rheostat, step down transformer, x ray tube, rotor
know what causes the pulsation in a single phase circuit
alternating change in voltage from 0 to max potential 120x each second
know how a 3 phase circuit/3 phase power works
addition of 2 more circuits made up of transformers and rectifiers at 120 degrees out of phase with each other
what does a 3 phase circuit provide
a wave form that never reaches zero = increased voltage
what is the end result of a 3 phase circuit
significantly less ripple and increased voltage
know why circuit breakers are included within a circuit
protect against short circuits and electrical shock
what autotransformers are
adjustable transformer controlled by kvp selected
how does the radiographer control the autotransformer
by selecting the kvp on the operators console
what does the autotransformer operate under
self induction
what is the primary purpose of the autotransformer
provide voltage that will be increased by step up transformer
the step up transformer changes….
Direct current to Alternating current
the step up transformer is the dividing line of the _______
primary and secondary circuits
where the 2 parts are located/what they are in the step up transformer
primary coil in the primary circuit and secondary coil in the secondary circuit
how does the step up transformer differ from the autotransformer
not adjustable and increases voltage by fixed percentage amount
why is the exposure timer is located in the primary circuit
easier to turn on/off at a low voltage
first variation of timer and explain it
synchronous timer, synchronous motor turns shaft at 60 revolutions per second and is the time it takes between on/off switch
second variation of timer and explain it
electronic timer, time it takes to charge a capacitor through variable resistor (most accurate and common)
third variation of timer and explain it
mAs timer, variation of electric timer but monitors current passing through x ray tube and terminates when desired mAs is reached located in secondary circuit
know how AEC works differently than an exposure timer
uses patients body part as the variable in determining whether to terminate the procedure
what AEC controls
quantity of radiation reaching the IR
know what secondary circuit begins with
secondary side of step up transformer
know what the milliampere meter is
device that monitors x ray tube current
know where and why tube is grounded
into earth to prevent electrical shock
what rectifiers are
device converts AC to DC
what type of rectifiers are most commonly used today
solid state rectifier
how we get best use out of rectifiers
arranged in pairs so that AC cycle has an open path from each direction
know what type of current is needed for transformer
alternating current (AC)
know what current must supply x ray tube
direct current (DC)
know how current flows inside x ray tube
from anode to cathode
know what the symbol means and stands for
diode: allows electrons to flow in only one direction
define half-wave rectification
one half of the AC cycle flows through the x ray tube and the other half is suppressed or blocked. Half the energy is used.
define full-wave rectification
4 rectifiers are used and both halves of the AC cycles are used. No energy is lost
define ripple
amount of waste measured at a given point
be able to describe how in a high frequency generator it converts the waveform to high frequency (2 steps)
the standard 60 Hz incoming power is first fully rectified and then sent through the capacitor bank and smoothed. Passes through and inverter circuit that chops DC and converts to high frequency AC
know what filament circuit starts with
Rheostat
define milliampere parameter
tube current that reflects rate of flow of electrons passing through the x ray tube during an exposure
be able to describe what happens when you adjust millamperage on operating console
adjusting the rheostat and the amount of resistance in the filament circuit and ultimately the amount of current applied to the filament
know the relationship between mill amperage and resistance
higher milliamperage = lower resistance
know the goal of the filament circuit
boil electrons off the filament wire
what would happen in the filament circuit if the current gets too high
the tiny wire could be damaged or destroyed
know the role of the rheostat
controls filament temperature and rate at which electrons boil off the filament
know the role of the timer
determines the duration of the process of electrons boiling off the filament
know the role of the step down transformer
increased current by reducing voltage that is applied to the filament
know the purpose of the filament circuit
control the degree and duration that the filament is heated, which in turn controls number of electrons boiled off which becomes tube current
know where the filaments are housed
cathode of the x ray tube
know how the filaments are represented on the console
large and small focal spots on the operating console, selecting the filament to be heated and used for that exposure
