High voltage Generator Flashcards
Used to change incoming power to levels needed to produce x-rays
High voltage section or generator
Generator is connected to the power line through a
Circuit breaker
Is used primarily for electrical insulation
Oil
In a step-up transformer secondary voltage is ____ than the primary voltage
Higher
Limits current from power line to generator
Circuit breaker
Responsible for increasing the output voltage from the auto transformer to the kVp necessary for x ray production
High voltage section/generator
High voltage generator operates only on what current
Alternating current
Voltage waveform is ____
Sinusoidal
The only difference bet. Primary and secondary waveform is their
Amplitude
Primary voltage is measured in ___ and secondary voltage is measured in ____
Volts (V)
kilovolt peak (kVp)
Primary current is measured in ___ while secondary current is measured in ___
Amperes (A)
milliamperes (mA)
What are the 2 types of current
Direct current
Alternating current
Derived from cell or battery and uni-directional
Direct current
Current changes its direction after equal intervals of time
Alternating current
The positive and negative terminals are FIXED
Direct current
NO FIXED TERMINALS as the current changes its direction after every half cycle
Alternating current
X-ray tube must be provided with ___ current
Direct current
X-ray are produced by acceleration of ___ from ____ to _____
Electrons
Cathode to anode
Secondary voltage of high voltage transformer must be ___
Rectified
Is a process whereby alternating current AC is converted into direct current DC
Rectification
Required to ensure the electron flow in one direction “from cathode-anode”
Rectification
Is an electronic device that allows current flow in only one direction
Rectifier
A device which performs the opposite function ( changes DC to AC) is known as ___
Inverter
Rectification is accomplished with ___
Diode
A ___ is an electric device that contains 2 ____
Diode
Electrodes
An ___ is a conductor through which electric current is passed. It may be wires plates or rods
Electrode
Solid state rectifier are made of ___ in most modern x ray generator
Silicon
Have the ability to conduct electricty
Semiconductors
2 types of semi conductor
n-type
p-type
Have loosely bound electron that are relatively free to move
n-type
Have space (holes) where there are no electrons
p-type
Middle portion or where the p and n type meet
Depletion region
The current that passes through the x ray tube exist only during the positive half of the cycle
Unrectified voltage
That is when the anode is positive and cathode is negative
Unrectified voltage
During the negative half cycle current flow only from
Anode to cathode
2 types of rectification
Half-wave rectification
Full-wave rectification
Is the simplest type of rectifier since it only uses one diode
Half-wave rectifier
Problems in half wave rectification
It wastes half of the electric power supply
It requires twice the exposure time
Consists of at least 4 diodes in high voltage circuit
Full wave rectification
For rectifiers arranged this way are called ___
Bridge rectifier
Advantages of
The exposure time for given technique is cut in half
The half wave rectified x ray tube emits only half of the time
The pulsed x-ray output of a full wave rectified machine occurs 120 times each second instead of 60 times per second as with half wave rectification
Another way to characterized the voltage waveform
Voltage ripple
Voltage ripple usually expressed as percentage of maximum ___
kV
Less voltage ripple results in a ___ radiation quantity and quality
Greater
3 common characteristic of electrical waveforms
Period
Frequency
Amplitude
Is the number of times the waveform repeats itself with in a one second time period
Frequency
Is the magnitude or intensity of the signal waveform measured in volts or amps
Amplitude
The length of time in seconds that the waveform makes to repeat itself from start to finish
Period
Period is also called as ___ the waveform from sine waves or the ____ for square waves
Periodic Time
Pulse Width
Unit of frequency
Hertz (Hz)
Single phase power results in a ____
Pulsating x ray beam
This is causes by alternating in swing in voltage from 0 to maximum potential 120 times each second under full wave rectification
SPP= Single Phase Power
Single phase input power results in ____
Pulsed radiation
X rays with SPP has a value of near zero are of little value because of lower energy
X ray with little penetrability
In ___ multiple voltage waveform are superimposed on one another resulting in a waveform that maintains a nearly constant high voltage
Three Phase Power
With ___ the voltage impressed across the X ray beam tube is nearly constant never dropping to zero during exposure
TPP
This produces a near constant potential voltage waveform improving image quality at lower radiation dose
High frequency generator
Power rating for three phase and high frequency
Power is measured in ___
kilowatts (kW)
Formula for power rating in TPP
PR= mA x kVp/ 1000
Formula for SPP
PR = (0.707) mA x kVp / 1000
