RAD 214 Radiographic Equipment

  1. Define Generator:
    Converts mechanical energy into electrical energy
  2. Define motor:
    convert electrical energy into mechanical enery
  3. Slip rings
    complete the alternating circuit in simple electric generator (attached to carbon "brushes")
  4. How long does it take for one full cycle to complete in an AC generator
    1/60 of a second
  5. Sine curve
    graph representing the sine of the angle between the plane of the armature and a plane perpendicular to the magnetic field
  6. Which pole influences the movement of the armature?
  7. A generator must have....
    • a powerful electromagnet
    • an armature
  8. a motor must have...
    2 interacting magnetic fields (one created by a current carrying wire, and an existing magnetic field)
  9. Values used to define resistance in an AC circuit...
    • Effective resistance
    • root mean square (rms) value
  10. Properties of resistance in a DC circuit?
    • Material
    • Length
    • Cross sectional area
    • Temperature
  11. Properties of impedence in an AC circuit..
    • Resistance (Material, Length, area, temp.)
    • Inductance reactance (Lenz's Law (back emf))
    • Capacitive reactance
  12. DC generators use _____ to complete the circuit?
    split-ring commutator
  13. Advantages of AC?
    • 1. Can be transformed
    • 2. Less power loss (through heat loss)
  14. Formula for power
    P (watts)= V (volts) x I (amps)
  15. Formula for power loss?
    PL = I2R
  16. Left hand thumb rule:
    • Thumb- direction of the electron flow
    • fingers- wrap in the direction of the magnetic field
  17. Right hand thumb rule:
    • Thumb- direction of the current flow
    • fingers- wrap in the direction the magnetic field
  18. Left hand generator rule
    • thumb- direction of the armature movement
    • index finger- direction of the magnetic field (S)
    • middle finger- direction of the electron flow
  19. Right hand generator rule
    • thumb- direction of the armature movement
    • index finger- direction of the magnetic field (S)
    • middle finger- direction of the current flow
  20. Left hand motor rule
    • thumb- direction of the armature movement
    • index finger- direction of the magnetic field (S)
    • middle finger- direction of the current flow
  21. Right hand motor rule
    • thumb- direction of the armature movement
    • index finger- direction of the magnetic field (S)
    • middle finger- direction of the electron flow
  22. Three types of Electic Motors
    • DC motor
    • synchronous AC
    • induction AC
  23. Two types of Generators
    • AC
    • DC
  24. Synchronous AC motor
    turns at the same speed as the armature of the AC generator supplying the current (or a multiple of the armatures speed) (used in clocks or timing devices)
  25. Induction AC motor
    • uses the stationary magnets of a stator, energized in sequence by a multiphase current, to interact through the motor principle with the copper bars (wrapped around an iron core) of a rotor
    • -uses no direct contact
    • -used for a rotating anode
  26. Typical speed of an anode?
    • 3500 rpm
    • -anode always spins at the same speed
  27. Transformer
    • -Changes the voltage of AC with no electrical contact or moving parts (electomagnetic induction principle)
    • -no appreciable loss of electrical enery (less than 5%)
  28. Types of transformers
    • Air core
    • open core
    • closed core
    • shell
  29. Air core transformer
    two insulated coils laying side by side
  30. Transformer Law
    • VS/VP =NS/NP
    • Voltage (emf) in the secondary coil is to the emf in the primary coil, as the # of turns in the secondary is to the # of turns in the primary
  31. Open core transformer
    • -iron core inserted in coils of wire
    • -experiences leakage flux (loss of magnetic flux at the ends of the iron cores)
  32. Closed core transformer
    • -heavily insulated coils called 'windings' wrapped around a square or circular iron core
    • -experiences transformer loss in the form of eddy currents
    • -lamination hinders the formation of eddy currents
    • -this is the type of transformer used for x-ray generating equipment
  33. Shell type transformer
    • -used as commercial or power transformer
    • -laminated silicon steel with 2 rectangular holes
    • -windings around central portion
  34. Types of Electrical power loss
    • -copper loss (I2R)- resistance
    • -eddy loss-heat generated by changing electical current (reduced by lamination w/silicon steel plates)
    • -hysteresis- heat generated by constant reorientation of magnetic dipoles (coercivity -requires energy to reorient poles [causes hysteresis] (reduced by silicone steel lamination))
  35. Autotransformer
    • -Varies input voltage to a transformer to control output voltage by selection of # of turns tapped on the secondary side
    • -sets your kV
    • -between source of AC and the primary side of the transformer
    • -single coil serves as primary and secondary
  36. Autotransformer Law
    seconday voltage/primary voltage= #tapped turns /#primary turns
  37. 2 circuits of the X-ray tube?
    • filament circuit- carries current to heat the filament
    • tube circuit-carries the current that passes from cathode to anode (electrodes) to produce x-rays
  38. Types of rectification (3)
    • Self-rectified
    • vacuum tube
    • solid state
  39. Self-rectification
    • -uses no diodes
    • -no protection for the filament
    • -self-half wave
    • -single pulse
    • -100% rippple with a pause
    • -forward bias (useful half of the voltage cycle)
    • -low heat loading capacity
    • -limited to low exposure factors
    • -100% suppression
    • -single phase
  40. One diode rectification
    • -half-wave
    • -one-pulse
    • -100% ripple w/ a pause
    • -100% suppression
    • -diode protects tube filament
    • -single phase
  41. 2 diode rectification
    • -single phase
    • -half-wave
    • -one- pulse
    • -100% ripple w/pause
    • -100% suppression
    • -increased load capacity
    • -increased effeciency
    • -increased filament protection
  42. 4 diode rectification
    • -full-wave
    • -2 pulse
    • -single phase
    • -100% ripple
    • -100% inversion
    • -high % of low energy x-rays produced
  43. Electron flow in diodes....
    from n to p
  44. Conventional electrical current flow in diodes.....
    from p to n
  45. What does a rectifier do?
    Converts AC to useable DC
  46. 3 energy bands in materials
    • -conduction
    • -forbidden
    • -valence
  47. commom semi-conductor and # of valence electrons
    silicon; 4 e-
  48. arsenic
    • -5 valence e-
    • -added to Si
    • -creates donor or n-type atom
    • -makes Si a conductor
  49. gallium
    • -3 valence e-
    • -added to Si
    • -creates acceptor or p-type atom
    • -makes Si an insulator
  50. barrier voltage or potential hill
    the potential difference that exists between a n-type ion and a p-type ion in a diode
  51. thyristor or silicon-controlled rectifier
    • -more complex
    • -2 p-type and 2 n-type layer (makes 3 n-p junctions)
    • -can hold or release large amounts of current
  52. Advantages of silicone rectifiers
    • -compact size
    • -no filament (means no filament transformer)
    • -low forward voltage drop
    • -low reverse current
    • -long life
  53. Main switch
    -primary side
  54. Fuses
    • -thin strip of metal prevents overload
    • -primary side
  55. Autotransformer
    • -changes voltage to set kV
    • -primary side
  56. Pre-reading kilovoltmeter
    • -Primary side
    • -metering device that indicates the desired kVp
  57. Timer /Exposure switch
    • -primary side
    • -controls the current to the primary coil serving to complete the x-ray exposure
  58. Remote control switch
    • -primary side
    • -completes the circuit
    • -protects the person making the exposure from electical shock
  59. Timer
    • -primary side
    • -built into the exposure switch
    • -5 types (mechanical, synchronous, electronic, mAs, and AEC)
  60. mechanical timer
    • -Primary
    • -operates by clockwork
    • -exposure time must be greater than 1/4 of a second
  61. Synchronous timer
    • -Primary
    • -powered by synchronous motor
    • -minimum exposure time is 1/60 sec.
    • -timer counts by waveform
  62. Electronic timer
    • -primary
    • -we use
    • -most sophisticated
    • -operate on variable resistance
    • -can be use for rapid serial exposure
    • -exposure time as small as 1 ms
  63. mAs timer/meter
    • -secondary (b/c it monitors actual tube current)
    • -factors time and mA to shut off at correct mAs
    • -not really a timer
  64. AEC timer
    • -primary
    • -measure quantity of radiation reaching the IR to provide the required optical density
  65. Back-up timer and Minimum exposure timer
    • -primary
    • -terminates the exposure in the event of AEC failure
    • -minimum exposure response time is 1 ms
  66. Circuit breaker
    • -Primary
    • -additional protection from overloading
  67. Filament Circuit
    • -primary
    • -supplies the heating current for the filament
    • -rheostat (variable resistor) reduces current to 3-5 amp and 6-12 Volts
  68. Filament Ammeter
    • -primary
    • -connected in series with the filament circuit to measure current (for proper heat production w/corresponding mA)
    • -space charge compensator automatically corrects to maitain constant mA over wide range of kV
  69. Primary coil of Transformer
    • -primary
    • -primary winding of the transformer
  70. Console
    • -primary
    • -
  71. Secondary Coil of transformer
    • -secondary
    • -smaller wires that primary b/c of smaller amps
  72. Miliammeter
    • -secondary
    • -connected in series with the high voltage/low amp secondary circuit of the transformer
  73. Rectifier
    • -secondary
    • -changes AC to DC
    • -increases heating capacity permitting larger exposures
  74. Cables
    • -secondary
    • -hazard reduced by insulation, grounding, and grounding of the secondary winding of the step-up transformer at its mid-point
  75. x-ray tube
  76. Anode
    • -secondary
    • -considered part of the x-ray tube
    • -contains stator induction motor
  77. 3 Phase Generator
    • -6 pulse-13% ripple
    • -12 pulse- 5% ripple
    • -Coils are wound in delta or star pattern
    • -primary is always delta
    • -secondary can be delta or star
    • -rated up to 1000 mA (kV max. 80)
    • -exposure time down to 1 ms
    • -nearly constant potential (small ripple)
  78. Hi-Frequency Generator
    • -1% ripple
    • -uses high-frequency circuit
    • -60 Hz converted to 500-25,000 Hz
    • -inverter circuits convert DC to square pulses
    • -Uses an inverter module
Card Set
RAD 214 Radiographic Equipment
radiographic equipment