Medium Frequency X Ray Generator
Also named high-frequency generator and inverter generator
Uses a high-frequency current to produce nearly constant potential voltage to the X ray
tube with a transformer of much smaller size than found in ordinary X-ray generators.
The incoming power supply to a medium frequency generator may be an ordinary 50 Hz
(230 V) single phase current (Fig.1).
The current is rectified and smoothed (YELLOW block below figure)
Current then fed to a chopper and inverter circuit which transforms the smooth, direct
current (DC) into a high-frequency (5 - 100 kHz) alternating current (AC). (The chopper
"chops" the continuous DC into high-frequency DC pulses and the inverter transforms
this into AC.) [Green block in below figure]
A transformer converts this high-frequency low-voltage AC into high-voltage AC, which
then is rectified by half wave rectification and smoothed to provide a nearly constant
potential high voltage to the X-ray tube. [ Blue block in below figure]
The voltage is controlled by varying the frequency of the chopper/inverter circuit, which
determines the frequency of the current delivered to the transformer. Fast exposure
switching, in the order of 1 ms, is easily obtained with the medium frequency generator.
It is important to be able to relate this working to the waveforms involved at each stage:
The electrical waveforms are shown below:
(Identify which waveform belongs to which component.)
Note esp the chopper-inverter which takes a DC waveform and produces an AC waveform.
The transformer amplifies this waveform.
The rectifier removes one half of this (so the waveform is once again a DC waveform).
The final smoothed waveform is then input to the X ray tube.