A bipolar DC power supply using full-bridge topology as active shunt for magnets

The Brazilian synchrotron light source has many current sources which are used to feed groups of series connected magnets. However, in several situations it is necessary to establish a low current difference among magnets of the same group, powered by the same power supply. That can be accomplished by using an Active Shunt in parallel with the magnet for which a different current setting is necessary. Recently a new model of current power supply was designed and tested. In the total 40 units of the new model were built and 36 were installed in the Light Source, operating as Active Shunts in parallel with quadrupole magnets. The chosen topology was the Full-Bridge, since it allows both adding as taking away current, so being able to work in all operation quadrants. The strategy to drive the switches was the unipolar PWM control, which does not cause current discontinuity near null output values, with lower ripple and THD and higher efficiency. Some calculations are showed as well as some experimental results, which show the satisfactory behavior of the power supply.