X ray generators

Introduction, Types

1. X-ray generators Mr Sujan Poudel B.Sc.MIT (2015) Department of Radio Diagnostic and Imaging

2. Outline Definition Components Types

3. Definition Generators means an electrical device which transform mechanical energy into electrical energy. But x-ray generator supplies electric power to x-ray tube. x-ray generator begin with the source of electrical energy. Radiology department will have 3 phase power available in range of 220V.

4. Components Transformer Rectifiers & capacitors Subsidiary circuit

5. Transformer Types of transformer used in x-ray equipment Auto transformer Filament transformer(step down transformer) High voltage transformer(step up transformer)

6. Generators types Types Single phase x-ray generator : uses single phase voltage source(220V) and produces two pulse DC waveform.

7. 3 phase six pulse generator : commercial electric power is usually delivered as three phase.

8. Contd …… phases 120 o apart Single Phase Power Three Phase Power

9. Contd.. Incoming 3-phase supply can be connected two ways : Star connection( wye connection):generally secondary winding of transformer. It has 3 phase and four wire system In which one wire is earthed(zero volt) So we can get line voltage ie 440 and phase voltage ie 220v Delta connection: generally primary winding of transformer is delta connected

10. Rectifier Convert AC into DC PN junction is used as rectifier where P and N are semiconductors When + ve end is connected to P side and - ve end is connected to N it is called forward biased .

11. Working of Segment AB In 1 st + ve half cycle when point A is (– ve ) and B is (+ ve ). Diodes R3 & R2 gets forward biased and R1& R4 gets reverse biased Flow of electron is from point A R3 Filament-anode R2 finally to (+ ve ) terminal B In next (– ve ) half cycle when point A is (+ ve ) and B is (– ve ) Diodes R1 & R4 gets forward biased and R3 & R2 gets reverse biased. Flow of electron is form point B R1 filament anode R4 finally to (+ ve ) end A.

12. 3 phase 12 pulse x ray generator To obtain 12 pulse from six phase an additional delta connection is added on secondary winding of transformer. So delta lags wye by 30 that means in each 30 phase difference a pulse is obtained. So, total 12 pulse can be obtained.

13. 4

14. Working of segment AB IN 1 st + ve half cycle of AC input Suppose end A becomes + ve and end B become –VE Diodes R1& R6 gets forward biased and diode R5 & R2 gets reversed biased Flow of electron from point B R1 xraytube R6 and to point A. After 30 output of delta is given out End A’ is + ve and B’ Is – ve Diodes R1’ and R6’ gets forward biased and diode R5’ and R2’ gets reverse biased.

15. Contd.. Flow of electron point B’ R1’ x-ray tube R6’ to + ve end A’. In – ve half cycle of AC input end A becomes – ve and B becomes + ve . Diodes R5 and R2 gets forward biased and diodes R6 and R1 gets reverse baised . Flow of electron from point A R5 x-ray tube R2 and finally to positive end B. After 3o degree delta circuit is activated.

16. Contd … High frequency x-ray generator : uses high frequency current to provide constant voltage to the x ray tube. Principle : when high frequency current is fed to primary winding of transformer it cause change in magnetic flux which produces high voltage EMF in secondary winding of transformer. Output voltage obtained i.e V is directly proportional to frequency to ac No of turns of transformer Area of iron core

17. Block diagram of high tension transformer

18. Advantages Independent of input power supply i.e it can operate either in single phase input or 3 phase input Has less ripple factor ie (1%) Compact in size so can accommodate in x ray tube housing

19. Power discharge generators Types Capacitor discharge generator : It uses high voltage capacitor to store the charge and when exposure is done discharging of capacitor occurs. Battery powered generator : It uses Ni-CD batteries to supply input power to x ray tube.

20. Working DC supplied by nickel caddmium batteries inverter high frequency AC Transformer high voltage AC Rectifiers high voltage pulsed DC Capacitor high voltage smooth DC X RAY TUBE USES Used in mobile x ray unit for ward radiography.