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Additional info: I want to reduce cryogenic boil-off, conductor peak quench temperature, and thermal stresses after a magnet quench. This is most desired when the stored energy gets above ~0.5 MJoule (due to long LHe recover times with a 200W refrigerator). Brute force can probably easily get me to 20kA @ 500V with the present SCR-commutation system Plan-B). Going beyond 500V with the present circuit requires piggy-backing the electrolytic cap bank... do-able but can be tricky, and requires lots of protection against overvoltaging the caps (which explode at 500V), and more real-estate for caps. The 1000V looks possible if I use mechanical contacts (combo of cooled silver for low resistance and silver tungsten for sacrificial arcing electrodes, provided I can time things adequately, and "blow-out the arc" with a rapidly-rising, strong magnetic field. Will probably be noisy too. IGBT's present a quiet option with precise timing, but a larger forward voltage drop than the other two. A hybrid contactor/IGBT might work if I can open the low-voltage contactor fast and far enough before the IGBT's need to open (>20ms after first warning). Lots of if's. Any info welcome on these or other ideas,
: I stumbled across your web-site while searching for information for
: high-current interrupters.
: I want to upgrade a high-current, ~1MJ inductor-interrupting switch in a
: cost-effective manner.
: Present system uses Parallel SCR's, with SCR cap-discharge commutation,
: and voltage-limiting energy-dump resistor: Imax.dc: 20kA
: Imax.commutation: 12 kA
: Vmax.interruption: 0.5 kV
: Voltage.rise-time: ~10 ms
: Opening jitter: < 2 ms
: Desired upgrade specs: Imax.commutation: 20 kA
: Vmax.interruption: 1 kV
: Voltage.rise-time: < 5 ms
: Opening jitter: < 5 ms
: Min.interruptions before maintenance: 100
:
: Brute-force upgrading the commutation system to higher voltage and
: current is likely to be costly, bulky, and increase the rise time.
: Likewise, an R&D project is likely to be prohibitively expensive.
: Are there other options (preferrably commercial systems) that might be
: adaptable for my purposes, e.g.,
: 1) contactor/transistor combo switches
: 2) contactor, magnetic blow-out switches
: Trade-offs?
: Al Lietzke
==============
:Bert's reply
: Hello Al,
: Sounds like an interesting problem. Fortunately the timing specs aren't
: too rigorous. I need to know a bit more about the environment that this
: system is imbedded within before I can suggest options. I'll contact you
: directly via eMail.
: Best regards,
: -- Bert --
:
:
Response to Bert's reply,
Thanks for your initial response
I have received no subsequent response, so I will post my reply in the event that something went wrong... or others want to contribute.
Superconducting magnet load (1-10mHy), usually dipoles and quadrupoles... hence a dc-current, that needs to be interruptable.
Al
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