Bipolar active shunt with bidirectional utility interface for the quadrupole magnets of Indus-2

Study for centering electron beam in Beam Based Alignment (BBA) method through quadrupole magnets is performed in the 2.5 GeV Synchrotron Radiation Source (SRS), Indus-2, at RRCAT. Each group of the series connected quadrupole magnets is powered by a precision current source (I_M). To perform BBA, the magnetic field of each quadrupole magnet has independently been varied by a few percent of I_M, through putting an active shunt across it. A prototype active shunt has been designed and developed for this purpose. The active shunt prototype was tested for its full load sinking and sourcing capacity of 6 A current at ±80 V. It was also tested during machine operation by connecting to a group of quadrupole magnets. The Performance of the shunt in terms of load current stability, sensitivity to disturbance, ripple, power-factor, line harmonics and power converter efficiency was evaluated during the testing. Pulse Width Modulated Rectifier (PWMR) is used as the input stage of the shunt, which is also helpful in achieving lower line current harmonic distortion and maintaining input power factor to unity over-wide operating current range. This regenerative utility interface has aided efficient four quadrant operation of the shunt.