NSRRC Activity Report 2023

096 NSRRC ACTIVITY REPORT 2023 shows the equivalent circuit of the BMPS with the load of the booster ring magnet. From the BMPS output terminals to the bending magnets of the booster ring, a comparable 2 μF capacitance is established, as depicted in the blue current path in Fig. 2 . During DC mode operation, a substantial amount of harmonic current is generated, as shown in Fig. 3(a) . At 2 kHz, the 80 mA harmonic current component clearly cannot meet the subsequent ramp tracking test requirements. To address these challenges, a Y-type common-mode filter was designed and incorporated to absorb the noise generated by residual parasitic capacitance along the ground solder path. The capacitances of these capacitors are significantly greater than those of parasitic 2μF capacitors, as shown in the red trace in Fig. 2 . This solution reduces the harmonic currents in the load current. The filter is installed before the DCCT to prevent harmonic current feedback into the control system. These improvements are shown in Fig. 3(b) , where the harmonic content in the 2 kHz output current is significantly reduced from the original 80 to 4.3 mA. 2 However, the substantial harmonic currents generated by the BMPS are guided to the ground through the capacitive effects of the dipole magnet load. This energy returns to the system through the BMPS ground current protection detector. However, when the harmonic current exceeds the ground current detector’s rated power, overload and damage occur. Additionally, the rated power of the ground current detector was increased to enhance its tolerance of harmonic ground currents. Control Card Synchronization Challenges In Fig. 4 , the high-precision analog differential signal modulation board on the COMMC card is shown. This component is primarily introduced due to the lack of external timing synchronization signals on the FPGA control card of BACMPS. While initial tests achieved a 3 Hz ramping operation, there were issues with the QMPS output current phase delay and waveform distortion, causing poor tracking of the BMPS output current by each QMPS in AC mode. This poor tracking highly impacting the current reproducibility at the injection point. To overcome these challenges, the BACMPS control card circuits were improved, which included a tarnsition from digital control modules to high-precision analog differential signal modulation boards. These boards allow external correction reference signals to adjust the phase and waveform of the BACMPS output current. 3 Ramping Current Waveform of BACMPS The power supply team successfully overcame numerous challenges during the operation of BACMPS. The BMPS and the QMPS energy were increased from 150 MeV to 3 GeV. The ramping current waveform of BACMPS is depicted in Fig. 5 , highlighting the significant contributions of the instrumental control team. A stable and 3 Hz Fig. 4 : High-precision analog differential signal modulation board on a COMMC card. [Photo courtesy of Bao-Sheng Wang] Fig. 3 : (a) Leakage current spectrum of the booster ring parasitic capacitance. (b) Improved booster ring parasitic capacitance leakage current spectrum. [Reproduced from Ref. 2]