High Voltage Generator (Part 2) Flashcards by Denina Martinito

Limits current from power line to generator

Circuit breaker

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Allows generator to be DISCONNECTED from power line

Circuit Breaker

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Used to change incoming power to needed levels

High Voltage Section/Generator

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Responsible for increasing the output voltage

High Voltage Section/Generator

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Used for ELECTRICAL INSULATION

Oil

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The secondary voltage is higher than the primary voltage

Step up transformer

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Generator operates only on ___

Alternating current

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In HVS the voltage waveform is

Sinusoidal

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Only difference bet primary and secondary waveforms

Amplitude

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Primary voltage is measured in

Volts

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Secondary voltage is measured in

kilovolt peak (kVp)

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Primary current is measured in

Amperes

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Secondary current is measured in

milliamperes

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Derived from a cell or a battery

Direct current

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The positive and negative terminals are fixed

Direct current

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No fixed terminal

Alternating current

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X-ray tube must be provided with

Direct current

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X-rays are produced by _____ from cathode to anode

Acceleration of electrons

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X-rays cannot be produced by electrons flowing in the ____

Reverse direction (anode to cathode)

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Process of AC is converted into DC

Rectification

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Ensure electron flow in one direction (cathode to anode)

Rectification

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Electronic device that allows current flow in only one direction

Rectifier

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A device that performs the opposite function (DC to AC)

Inverter

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Electronic device that contains two electrodes

Diode

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Conductor through which electric current is passed

Electrode

Electrode may be

Wires Plates Rods

Made of silicon

Solid state rectifiers

Have the ability to conduct electricity

Semiconductors

Have loosely bound electrons

n-type

Spaces (holes), no electrons

p-type

If higher potential is placed in the p-side of the junction,

Electrons and holes will migrate towards the junction

Flow of electrons and holes constitutes an _____

Electric current

If positive potential is placed on the n-side,

Electrons and holes will be swept away from the junction

No flow of electrons

No electric current

Unrectified voltage

Alternating current

In unrectified voltage, the current that passes through the X-ray tube during

Positive half cycle

During the negative half of the cycle

Current can flow only from anode to cathode

Not constructed I emit electrons

Anode

Simplest type of rectifier

Half wave rectifier

Uses one diode

Half wave rectifier

During the positive portion (half wave)

Allows electric current to pass through the X-ray tube

Negative portion (half wave)

No electric current

Problems of half wave rectification

Wastes half of the electric power supply | Twice the exposure time

Consists of atleast four diodes

Full wave rectification

Four rectifiers are arranged in

Bridge rectifier

The negative half-cycle (full wave) corresponds to

Inverse voltage is reverse

In full wave rectification

Anode is always positive

No gaps in the output waveform

Full wave rectification

All of the input waveform is converted to

Usable output

Pulsed X-ray output of a full wave rectified machine occurs

120 times each second

Another way to characterized the voltage waveform

Voltage ripple

Percentage of maximum kV

Voltage ripple

Less voltage ripple =

Greater radiation quantity and quality

Length of time in seconds that the waveform takes to repeat itself

Period

Waveform for sine waves

Periodic time

Waveform for square waves

Pulse width

Number of times that the waveform repeats itself

Frequency

Reciprocal of the time period

f = 1/T

Unit of frequency

Hertz

Magnitude or intensity of the signal waveform

Amplitude

Amplitude is measured in

Volts or amps

Voltage waveforms are produced by

single-phase electric power

SPP results in a

Pulsating X-ray beam

Single phase input power results in

Pulsed radiation

X-rays produced with SPP has a value near zero

Little value because of lower energy

Disadvantages of pulsed radiation

Only significant when voltage is near peak | Produce low-energy photons (contribute to dose)

Multiple voltage waveforms are superimposed on one another

Three-Phase Power

All three wires :

Carry the same current | Constantly balanced power load

Usually operates at 500 to 25,000 Hz

High frequency generator

Uses inverter circuits

High frequency voltage generator

Inverter circuits which are high speed switches converts

DC into a series of square pulse

Much smaller than 60Hz high voltage generator

High frequency generator

Produces a near constant potential voltage waveform

High frequency generator

Measured in kilowatts (kW)

Power

Generator connected to power line through a _____

Circuit breaker