A novel topology for the bending magnets power supply at LNLS

The synchrotron radiation source under construction at the LNLS in Brazil is composed of 12 bending magnets and 3 quadrupole families. A new topology for a high-performance DC current power supply was developed to feed the magnets. The main goal is to get high performance in an efficient and reliable system. To achieve these goals, the topology was based on a modular switched-mode power supply (SMPS) associated in series with a 6 pulse silicon controlled rectifier (SCR) bridge. To reduce possible high levels of electromagnetic interference, only a small fraction of the total load voltage is used to feed the SMPS. More than 90% of the power is delivered by the SCR bridge. The load current is shared among the SMPS modules, so that each one switches only a fraction of the total current. Each module is built inside a metallic box that shields the electric and magnetic fields. The SMPSs are controlled by current limit modulation. A 18-kW prototype was built and has been used in the laboratory to characterize the magnets. Measurements indicated a mean current stability of ±14 ppm, current ripple was ±25 ppm, and the field ripple was less than ±1 ppm inside the vacuum chamber. The tracking error was null. The power factor was 0.95 and the efficiency was better than 90%