I'm reading a paper on a superconducting magnetic energy storage (SMES) power control system. One large superconducting inductor (L1 in the figure below) is charged up by a 10kA power supply. Once charged, L1 is isolated from the power supply (Sw1a & Sw1b are switched off) and connected to the DC chopper circuit with switches Sw2a & Sw2b. The chopper circuit transfers the energy to SMES inductor L2 with a switching frequency of 300Hz. The energy is then stored in L2 or transferred back to L1 again with the chopper circuit. This serves as a demonstration of transferring energy between SMES systems.

I’m confused with how the DC chopper operates specifically. I’ve tried to picture different switching scenarios where one or two IGBTs are off and the others are open. What is the order of how the switches S1, S2, S3, and S4 are operated in the attached figure? Is the purpose of the chopper is to split up the DC output and isolate L1 from L2 so all the energy from L1 can be transferred to L2? For reference the paper is "Energy Transfer Experiments between 3 and 4 MJ Pulsed Superconducting Magnets" by T. Onishi, 1985. enter image description here


Background ~ This experimental power supply says in the abstract , (which was (all ) I had access to) that it was for a superconductor lines to an Ohmic heater of a Fusion Reactor for a short high temp test.

“ energy transfer experiments between a 3 MJ magnet (load magnet) and a 4 MJ magnet energy storage magnet) using a chopper-type energy transfer equipment. The test goal was to confirm the technical feasibility of operating an ohmic heating coil for a tokamak-type fusion reactor. A 3 MJ magnet was first charged to 4510 amperes in 1. 5 seconds. It was discharged to 0 ampere in 1. 5 seconds and at once was re-charged to minus 4510 amperes in 1. 5 seconds. It was again discharged in 1. 5 seconds”

The quad or full bridges switch on the high side and can be PWM modulated on Lo side. I suspect this is for step-down voltage to be <= DCR of secondary coil . But same Amperage. Not sure since I could not access the full text.

  • \$\begingroup\$ Yup. I know the background of the paper and the application of it. Still, they don't explain how the chopper circuit switches operate. This chopper configuration is common in other SMES discharge circuits as well, but I cannot find much about it. \$\endgroup\$ – Jeremy Adams Aug 19 '19 at 13:18
  • \$\begingroup\$ Regenerative Brakes use BEMF to battery then when ineffective , shunt coil with re-arrangement of half bridges. There are thousands of articles on this , so you must be using wrong academic or Scholar search engine Microsoft, google academic or ResearchGate or more likely wrong key words. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 19 '19 at 15:19
  • \$\begingroup\$ I did not know regenerative brakes used similar DC chopper circuits. Otherwise, there are limited papers on SMES chopper operation. It sounds like you know about this topic so please recommend some papers (pdf links if possible) or draft a cohesive answer to my original question. It'd be great if you could explain "The quad or full bridges switch on the high side and can be PWM modulated on Lo side." What switches does this apply to, what are the high and low sides your referring to, etc.? \$\endgroup\$ – Jeremy Adams Aug 19 '19 at 18:15
  • \$\begingroup\$ While I am in post Op bypass surgery to shoulder artery , I’ll expect you to learn how to learn. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 20 '19 at 0:00

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