High stability switching mode power converters for magnet loads

The availability of general purpose switching mode power supplies in the KW range has prompted the possibility of using them for powering optical elements in linear accelerators. They are, however, not designed specifically to be operated as high stability current sources into inductive Loads. The authors have modified and conditioned commercial, off the shelf switching mode power supplies for use in powering multipole magnets. Temperature stability in the constant current mode has been upgraded to 15 ppm/C. Other stability parameters have been similarly improved. They modeled power supply operation using the program SPICE, and verified its results experimentally. An analog controller was designed to compensate for instabilities in the feedback loop. This circuit was incorporated into a Bitbus power supply controller which is used as interface to the control system. Analysis of shielding techniques and tests results for a 2.5 KW power supply are provided