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Rad T 110

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Single Phase Electric Current Full Half Voltage ripple Three phase Electric Current 6 pulse 12 pulse Voltage ... Step-down transformers These transformers ... – PowerPoint PPT presentation

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Title: Rad T 110


1
Rad T 110
  • Electromagnetic Radiation

2
The Wave Equation
  • Velocity frequency x wavelength
  • Remember, photons all travel at the speed of
    light, 186,000 miles/second so velocity is in
    effect a constant
  • Consequently, any changes to either frequency or
    wavelength have to be accompanied by a change in
    the other.

3
  • So, if frequency increases then wavelength
    decreases.
  • Conversely, if frequency decreases then
    wavelength increases.

4
What is frequency?
  • Frequency is defined as the number of wave forms
    per second.
  • In the case of x-ray photons about 1019 cycles
    per second.
  • Frequency is a representation of energy.
  • As beam energy is increased, frequency increases.

5
Beam Energy
  • Beam energy is determined by kVp.
  • Therefore, the higher the kVp the higher the
    photon frequency.
  • The higher the kVp
  • The higher the beam quality
  • The harder the beam
  • The higher the penetrability of the beam

6
Electromagnetic Spectrum
7
Wave-particle Duality
  • Higher energy photons act like particles.
  • Low energy photons act like waves.

8
Inverse Square Law
  • Addresses the issue of the divergent beam.
  • As the beam travels it diverges or spreads out.
    The further it travels the more spread out it
    becomes.
  • However, given that the same number of photons
    are in the beam their concentration or intensity
    will be diminished.

9
Single Phase Electric Current
  • Full
  • Half

Voltage ripple
10
Three phase Electric Current
  • 6 pulse
  • 12 pulse

Voltage ripple
11
Electromagnetic Induction
  • Faradays Law
  • An electric current is induced in a circuit if
    part of the circuit is in a changing
    (alternating) magnetic field.
  • Also, a magnetic field can be generated by
    alternating magnetic fields.

12
Transformers and Mutual Induction
  • Transformers work with AC current through the
    application of Faradays Law.
  • An AC electric current induces a varying magnetic
    field in a piece of iron (electromagnet).
  • Another piece of wire is wrapped around the iron.
    In this wire an electric current is induced.
    Why, because the magnet field is moving
    throughout the iron.
  • So, without an AC current you would not induce a
    varying magnetic field.

13
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14
Step-down transformers
  • These transformers also work on the principle of
    mutual induction however, their goal is to
    decrease the incoming voltage.
  • So, the secondary side has fewer windings than
    the primary side.
  • Any device you have at home that runs on
    batteries and AC has a step-down transformer. It
    is usually the little black box that gets hot.

15
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16
Step Up Transformers
  • These transformers are intended to increase
    voltage.
  • Remember, incoming voltage is relatively low
    (lt480 V) is in order to create kVp you are going
    to have to dramatically increase the voltage.
  • This is done by having more wires on the
    secondary side of the transformer than the
    primary side.

17
  • The primary side of the transformer is were the
    voltage comes in.
  • The step-up transformer can also be called a
    high-voltage or high-tension transformer.

Closed core transformer
18
Types of Transformers in X-ray Circuits
  • Autotransformer
  • Has only one winding and works on the principle
    of self-induction (because of the single
    winding).
  • Step-up transformer, high voltage or high tension
  • Step-down or filament transformer
  • Both of these are generally shell type
    transformers and work using mutual induction.
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