X ray generators and its type

this is about the generators used in xray circuits

1. GENERATORS AND ITS TYPES DEEPAK NEGI MRIT TMU

2. INDEX INTRODUCTION COMMON TERMS OF ELECTRICITY (CURRENT , VOLTAGE , E.M.F , A.C , D.C , RECTIFIER , p.n junction) GENERATOR WORKING OF GENERATOR XRAY GENERATOR 3 PULSE 6 PULSE, 6 RECTIFIER 12 PULSE RIPPLE FACTOR ADVANTAGE AND APPLICATIONS

3. GENERATOR A device which converts mechanical energy into electricity. First discovered in 1831, by MICHAEL FARADAY . A BRITISH SCIENTIST. They use to work on electrostatic principle.

4. COMMON TERMS OF ELECTRICITY CURRENT:- The flow of electrons in a closed path from one atom to another. Ampere (A)-SI Unit. It is also know as Potential, which is basically the work done by current. VOLTAGE:-The work done to move the charge from one point to another is called voltage or POTENTIAL DIFFERENCE. EMF(electro motive force):-The force which allows the continuous flow of current.

5. Continue….. A.C (alternating current):- The current which periodically reverses direction and changes its magnitude with time. D.C (direct current):- A uni -directional flow of current.

6. Continue… RECTIFICATION:- The process of changing A.C to D.C . RECTIFIER :- The device which convert A.C to D.C . 2 Types of Rectification HALF-WAVE RECTIFICATION:- Allows one half cycle of an AC voltage waveform to pass , blocking the other half cycle. FULL-WAVE RECTIFICATION:- Allows AC to convert into pulsating DC voltage for use in power supplies.

7. p -n junction P and N type are diffused into a single crystal. The N type is rich in electrons and P in holes , so the electrons diffuse across the junction. It is also called Solid State Rectifier.

8. Continue…. DIODE:- A two terminal electronic component that conducts current primarily in one direction. Has low resistance in one direction , and high on the other.

9. GENERATOR A device which converts mechanical energy into electric energy.

10. Working of Generator According to Faraday’s law of electromagnetic induction , when a conductor links with a changing flux , it will have an induced emf across it. The value of induced emf across the conductor depends on the rate of change of flux linkage with the conductor . The direction of the induced emf in the conductor can be determined by Fleming’s Right Hand Rule .

11. Continue when we rotate single loop of a conductor in a magnetic field . At point A the loop is in rest an no current is induced into it . As it rotates and move to about an angle of 90 the maximum lines of magnetic flux interact with the loop and current is induced in this point (B). Again when it rotates to 180 degree almost no magnetic field lines interact with the coil and no current is induced . Point (C) Now the coil rotates to 270 degree again magnetic flux interacts and current is induced . Point (D) Finally it rotates 360 degree and comes to rest again.

12. X-RAY GENERATOR X-RAY Generator provide electric power to the tube. Tube requires electric energy for 3 purpose . To emit electrons from the filament. To accelerate these electrons from the cathode to the anode. A time mechanism , which regulates the length of the xray exposure. The mechanism of an xray generator is in 2 separate components. A control panel (console) Transformer assembly.

13. TRANSFORMER Used to alter voltage and current .

14. AUTO-TRANSFORMER:- The voltage from the main supply passes through the auto-transformer, which supplies it further to other components as per the requirement. STEP-DOWN TRANSFORMER:- Heats the filament. STEP-UP TRANSFORMER:- Provides potential.

15. 3 PHASE GENERATOR In this 3 coils are incorporated at an angle of 120 degree to each other. Coil 1 is moving with the lines of magnetic force and consequently no e.m.f . is being induced. Coil 2 has passed point B at which maximum voltage was induced and its e.m.f . is reducing towards zero value. Coil 3 is approaching the point where the voltage reaches its maximum.

16. 3 PHASE GENERATOR

17. SIX PULSE, SIX RECTIFIER T he three-phase (six-pulse) generator is connected to three live phases. Primary transformer employs a delta wound. Secondary transformer with a wye wound . The output of the secondary winding is Rectified with a six solid state rectifier.

18. SIX PULSE , TWELVE RECTIFIER Uses 2 sets of secondary windings in the wye or star winding . Consists of 2 six pulse bridge circuits connected in series . Primary winding uses delta winding. 12 Rectifier works as 6 full wave bridge .

19. TWELVE PULSE A twelve-pulse transformer looks similar to the six-pulse , twelve-rectifier transformer. The difference is that the secondary is not a Double wye connection . it is a wye and a delta connection. Delta lags the wye by 30 degree.

20. RIPPLE FACTOR The ripple factor is the variation in the voltage across the x-ray tube expressed as a percentage of the maximum value. Single phase = 100% (voltage goes from 0 to maximum) Six pulse =13.5% Twelve pulse=3.5%

21. Advantages of the three-phase over single-phase circuits (1) more X-rays, (2) X-rays of shorter average wavelength than the single phase unit, even though kVp and mA are the same In each case . single-phase voltage is at or near zero point at the beginning and end of each half cycle, the rectified three-phase voltage is close to peak value at all times and never drops to zero value.

22. Radiographic advantages of three-phase X-ray generators compared to those operating on single-phase As the kV remains constantly at a high value during the exposure (1) Less soft radiation is produced, resulting in a reduction in skin dose to the patient. (2) More X-rays are produced for a given m A . (3) Because of more xrays the same film dose, e.g. radiographic exposure , can be achieved in a shorter time. Therefore reduction in exposure times is achieved. (4) Improved tube rating is achieved at short exposure time. (5) The X-ray tube has a longer life due to more even thermal loading.

23. REFERENCE Equipment's in Diagnostic radiology – E.Forster Christensen’s physics of diagnostic radiology