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Physics, Techniques and Procedures

Ripple factor

the variation in the high-voltage expressed as the percentage of the maximum high-voltage across the X ray tube during X-ray production:

Ripple factor (%) = 100 x (Vmax - Vmin)/Vmax

The ripple causes corresponding but relatively higher variations in the X-ray output. It is an unwanted phenomenon in the X-ray production due to the lengthening of the exposure time and the reduction in the average kV. The ripple is theoretically 100% for the old-fashioned single phase X ray generator (in practice, it is less, however, due to the smoothening effect of the high-voltage cable capacitance). The three-phase X-ray generator have ripple factors in the range of about 3-25% (3-phase 6-pulse generator: 13-25%, 3-phase 12-pulse generator: 3-10%). In the medium frequency generator, the ripple factor decreases with increasing kVp. In this type of generator (also named high frequency or inverter generator), the kV is controlled by adjusting the frequency of the current prior to high-voltage transformation. Ripple is usually in the range of 4-15%. There is practically no ripple in the constant potential X ray generator.

AK