Rad Tech 110

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Rad Tech 110

• Circuits

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Conditions Necessary X-ray Production

• High voltage
• In the kilovoltage range
• Electrons
• A supply of electrons
• A need to stop the electrons suddenly

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Types of Transformers
Shell type
Core type
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How do transformers work?

• They can only work using AC current
• On the principle of induction
• Mutual
• Self
• The basic premise is that AC current induces
  alternating magnetic fields.

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Transformers work?

• These alternating magnetic fields are distributed
  throughout the core of the transformer.
• The alternating magnetic fields induce an
  electrical current in loops (coils) of wire.

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What gets transformed?

• Both voltage and current
• In a step-up transformer the voltage is increased
• The primary side (incoming) has less coils than
  the secondary (outgoing) side.
• Because there are more coils on the secondary
  side a higher voltage is produced
• Increases voltage is reflected as a higher
  amplitude of the waveform.

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• At the same time as voltage increases the current
  correspondingly decreases.
• This occurs due to the conservation of energy.
• If you increase one aspect, voltage, you have to
  decrease the other, current.
• (Voltagep)(currentp)(voltages)(currents)

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Step down transformer

• Here the primary side has more coils than the
  secondary side.
• The result is a decrease in voltage through the
  transformer.

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The X-ray Circuit
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Three sections of the x-ray circuit

• Operating (control) console
• High voltage generator
• X-ray tube

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Operating (control) console

• Line voltage compensator
• Autotransformer
• kVp selector
• mA selector
• Timer
• Pre-reading kVp meter

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Line voltage compensator
The purpose of the line voltage compensator is to
maintain a constant voltage to the system. In the
modern system this is done automatically.
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Autotransformer
The autotransformer works on the principle of
self-induction. It has a single core and is
responsible for varying the voltage. Because of
its ability to adjust voltage, the
autotransformer can be either a step-up or
step-down transformer.
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kVp selector

• kVp is adjusted at the autotransformer
• Taps are available so that different voltages can
  be achieved.

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Pre-reading kVp meter

• The kVp meter is considered pre-reading because
  it is not actually measuring kVp but measuring
  voltage off the autotransformer.
• Remember, the autotransformer is used to adjust
  voltage.

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Timer

• Historically, there have been many types of
  timers.
• Today, all timers are electronic timers of
  various types.
• mAs
• Phototiming (AEC)
• Regular electronic

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mA selector

• Allows for adjust of the filament voltage
• Precision resistors
• Choke coil

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High Voltage Generator

• Step-up transformer
• High voltage transformer
• High tension transformer
• Step-down transformer
• Filament transformer
• Rectifiers

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Step-up Transformer

• This transformer is responsible for producing the
  high voltages necessary for x-ray production.
• Turns ratio of 5001 or 10001

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Filament Transformer

• Intended to lower voltage and increase current
• Allows for thermionic emission to occur at the
  filament
• Ultimately, provides the electrons necessary for
  x-ray production.
• Tube current measured in mA.

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Rectifiers

• Current traffic cops
• Intended to allow electrons to flow in only one
  direction
• Provide the mechanism that converts AC to DC
  current.
• 4 rectifiers are required to fully convert AC to
  DC.

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Types of Circuits

• Single phase
• Full wave
• Half wave
• Three phase
• 6 pulse
• 12 pulse
• Medium and High Frequency
• Capacitor discharge
• Found predominantly in portables.

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Single Phase

• Full
• Half

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Three phase

• 6 pulse
• 12 pulse

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Three phase transformers

• Three phase units use delta and wye
  transformers
• 6 pulse
• 2 wye and 1 delta
• 12 pulse
• 2 delta and 1 wye
• They also require 12 rectifiers

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Advantages of 3 phase

• Higher beam quantity and quality
• Higher mA stations are also possible

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Why higher quantity and quality for three phase?

• Because the voltage ripple is less
• Basically when the tube is energized it stays
  energized.

full
3 phase 12 pulse
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Medium/High Frequency Generator