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1. FUNCTIONING OF TRANSFORMER
CONROL PANEL
X RAY TUBE

2. PRESENTORS
Ayesha malik
Kamran Nosher
Adnan Ahmed
M. Saeed
Abbas Ali
Areeba Ubaidullah
Ali Faizan
Irfan Manzoor
Affan Nadeem
Hamza Sakhawat

3. Transformer :
An electromagnetic device use for
increasing and decreasing the
voltage of incoming electrical
energy without much loss.
Transformers transform electrical
energy from one circuit to another
by electromagnetic induction.

4. Need for transformer
Usual voltage supply is 220 with 60 Hz frequency while X Ray
machines are designed to work at 440 volts.
Electron acceleration requires : between 40000-150000 V.
Principle :
The principle for functioning of transformer is “Electromagnetic
Induction” that is production of an electromotive force across an
electrical conductor in a changing magnetic field.

5. • When current flows through the primary coil of Transformer , it
creates a magnetic field within the core, this magnetic field
induces a current in the secondary coil.
• Current flows through the secondary coil only when the
magnetic field is changing ie: increasing / decreasing.
No current flows when the magnetic field in core is in a steady
state.

6. Components of Transformer :
1. Primary coil:
A set of insulated wires attached to the
input current.
2. Iron core :
The conduit for the changing magnetic field.
3. Secondary coil :
Set of insulated wires attached to the output
current.
The primary and secondary coils both have
winding turns which will vary in number
with respect to each other depending on the
type of transformer

7. Transformer Of X-ray Machine
Auto-transformer:
• Adjusts voltage coming from
main line. ( kV selection)
• Usually automatic on modern x-
ray machines.
• It has single coil. (Principle: Self
induction)

8. • X-ray tube require high voltage
supply for electron emission.
• Step-up transformer converts low
voltage to high voltage, there are
more number of windings in
secondary coil.
• Higher the voltage, more the
contrast of the X-ray image.
• The ratio of the incoming voltage
to outgoing kilovolts is
proportional to the number of
turns on both the primary and
secondary side (Vp/Vs = Np/Ns).
Step Up transformer:

9. Rectification
● Conversion of AC to DC.
● Rectification is used in order that a reverse voltage is not
applied across the X-ray tube.
● AC required for functioning of transformer but the X-ray tube
requires constant current so AC is converted to DC and supplied
to anode.
● In modern X-ray machines high frequency rectification is used,
so there is no ripple formation (drop of voltage).

10. Step down transformer
• Filament circuit requires high amperes.
• Step down transformer converts high voltage to low
voltage or high amperage and provides to cathode.
• Number of windings in primary coil > Number of
windings in secondary coil.

11. CONTROL PANEL:
It is a separate unit connected electrically to
the X-ray machine.
• It contains meters & switches to select kVp(
penetrating ability of x-ray beam),
mA(number of x-ray photons in x-ray beam)
and exposure time.

12. • COMPONENTS OF CONTROL PANEL
1. ON/OFF SWITCH:
• It is a main switch to turn the unit ‘on’. The switch permits
flow of current to the tube at ‘on’ position and prevents at
‘off ‘ position.
• For the safely of the X-ray tube and also to avoid an
accidental exposure, the switch should remain in ‘off ‘
position when machine is not being used.
• Voltmeter and voltage compensator control:
• Most X-ray machines are designed to operate on a 440
voltage power source.
• A voltmeter measures the voltage of electric current and
voltage compensator allows adjustment of voltage.

13. • KILO VOLTAGE SELECTOR:
• It allows precise selection of desired kV.
• In some machines this control is automatically linked to
a certain milliamperage (mA) value. In such a case, a
high kVp(penetrating ability of x-ray beam) is available
at a relatively low mA (Number of x-rays in abeam) and
vice versa.
• EFEECTS OF KILOVOLTAGE:
• The higher the kilovoltage, the more rapidly the
electrons travel.
• The greater the amount of energy released, shorter
the wave –length of the X-rays produced .

14. • Timer & Exposure button:
• The quantity of X-rays reaching the film is directly related lo the X-
ray tube current and the time for which the tube is energized i.e.
The exposure time.
• The range of exposure time in available machines is as short as
0.001 second.
• An exposure device mostly consists of a two-stage,
• Exposure button of first half depression rotates the anode and
activates the filament.
• Complete depression, after a short pause, causes actual
radiographic exposure.
• The exposure button should be attached to the control panel by a
length of cable so that the person making the exposure may
position himself at a safe distance.

15. Safety devices
• Switches: Three switches mainly operated by the technician:
1. Main switch: By operating the main switch, one can isolate whole X-ray machine from the
electrical supply.
2. The on-off switch: provided in the control panel, energizes the autotransformer and many
auxiliary circuits such as of meters, filament etc.
3. Exposure switch needs constant pressure in order to help it on ‘ON’ position.
• Fuse & Switches:
• A fuse is a thin wire encased in a glass tube with sealed metal ends which are in contact with the
electrical circuit.
• The thin wire of the fuse melts if a current higher than required flows through. Fuse is included
either in the casing of main switch or in X-ray circuit immediately before the autotransformer.

16. X-Ray Tube
 > The X-ray tube is the single most important component of the
radiographic system.
 It is the part that produces the X-ray.

17. The Production of X-ray
X-ray are produced when fast moving electrons are stopped by
means of a target material.
The moving electron possesses kinetic energy.

18.  When the electron is suddenly stopped, its
kinetic energy is converted into heat and X-
ray.
>Therefore, the interaction of electron with
the target is the basis for x-ray production.
>If the voltage between the anode and the
cathode is increased.

19.  > The electron will accelerate faster thus
results in higher energy x-ray will be
produced.
>up to 99% of the kinetic energy of the
electron is converted into heat.
Whilst only 1% converted into the x-ray.

20. X-ray Components
1. Glass envelope
2. Protective housing
3. Cathode (filament & focusing
cup)
4. Anode
5. Focal spot
6. Beryllium window
7. Tube housing

21. 1. Glass Envelope
 The glass envelope is made of Pyrex glass.
 > Glass envelope is highly evacuated and sealed.
 1. Cathode assembly 2. Anode assembly
 The Anode and Cathode are housed inside a glass
tube.

22. 2. Protective housing
The X-ray tube is covered in a lead lines metal protective housing.
The X-ray photons are generated isotropically or in all directions.
The housing is designed to limit the beam to window .
The housing contains oil that serves as an insulator, also it dissipates
the heat and cools the anode.

23. 3. Cathode
The cathode is a negative electrical charge side of the tube.
Cathode is composed of a tungsten filament which is embedded
in a focusing cup.

24.  Contains two major components:-
1. Filament
2. Focusing Cup

25. 1. Filament
Filament are usually made
of thoriated tungsten wire.
Because tungsten has a
very high melting point.
Because tungsten provide
for higher thermionic
emission than other metals.

26.  In modern x-ray tube dual filament is used.
:: the filament is a coil of wire similar to that
in a kitchen toaster except much smaller.
:: The filament is usually approximately 2mm
in diameter and 1-2 mm long.
:: length – less than 1cm.
:: when the filament is heated to white light, it
emits electrons.
:: Its melting point is 3410 degree centigrade,
and therefore it is not likely to burn out like the
filament of a light bulb.

27.  2. Focusing cup
> The filament is embedded in a metal cup Called the focusing cup.
> Focusing cup is made from nickel.(Light weight)

28.  The focusing cup focuses the electrons to the
target which are produced by the filament.
:: without the focusing cup, the electrons
become spraesd off.
:: the focusing cup also protect the adjacent
parts of the tube wall from damage by electron
bombardment.

29. 4. Anode
 Positively charged
electrode.
 Opposing
the
cathode.
High density metal
target.
 It is made up of
tungsten.

30. Types of Anode
1. Stationary Anode
Stationary anode is used in dental
x-ray unit, portable x-ray unit and
Made of tungsten
 2-3mm thick
 Embedded in large mass of copper
 Consist of a one filament
 Triangular & Rectangular shape
 Anode angle = 15-20 degree
 Dimension greater than 1cm.
where low power exposures are
required.
Why use tungsten:
High atomic number (74)
High melting point (3387 C)
It does not easily vaporize.
It has good thermal conductivity.
High density.

31. Types of Anode
2. Rotating Anode
Made of tungsten or alloy of
tungsten with rhenium.
Has beveled edge.
Angle of bevel is 16-20 c.
The angle makes easier for the
x_ray to be emitted in a downward
direction.
Speed of rotation is 3000rpm
practically.
Rotating anode is production of x-
ray at high intensities.
Higher tube currents and shorter
exposures times.
Rotating anode half life depends
on roughing and pitting of surface
of anode exposed to electron
beam.
The rotating anode assembly
consists of the anode, anode stem,
bearing, stator, rotor, focal spot.
The rotating anode allows the
electron beam to interact on a
much large target area during the
exposure .

32. Anode Stem
Made up of molybdenum
It has high melting point but poor conductor of heat.
It protects ball bearing from undesirable heat.

33. Bearing
Bearing increases life of the tube.
Lubricant used in silver.
Silver is suitable in vacuum.

34. Stator
The stator is located outside the glasses envelope.
Consists of a series of electromagnets equally spaced around the
neck of the tube.

35. Rotor
The rotor is inside the glass envelope is a shaft made of bars of
copper and soft fabricated into one mass.

36. 5. Focal spot
It is the area on anode.
Where the electron bombard and x-ray are produced.
Two Focal Spot: 1. Small focal spot 2. Large focal spot

37. 6. Berylium window
X-ray tube window is made from beryllium.
Beryllium is preferred because it has low density and low atomic
mass, and hence very low absorption of x-rays.
7. Tube Housing
Visible part of tube
It is a metal case consists of aluminum alloy.
It is lead lined which protects and supports the glass tube and
provides shielding from radiation.
Leakage limit -100mR/h at 1 meter.