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What caused the problem? What are the symptoms ? Solution (if any) …?

What caused the problem? What are the symptoms ? Solution (if any) …? Potential existence of same problem in similar circuits?. Quench-like trips of RSS.A78B1/2…. RSS.A78B1/2 tripped twice during pre-cycling/heat runs, indicating an increase of current just before tripping

alana-cervantes
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What caused the problem? What are the symptoms ? Solution (if any) …?

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  1. What caused the problem? • What are the symptoms ? • Solution (if any) …? • Potential existence of same problem in similar circuits?

  2. Quench-like trips of RSS.A78B1/2… RSS.A78B1/2 tripped twice during pre-cycling/heat runs, indicating an increase of current just before tripping RSS.A78B2 on 16th of February @ 04:16:56 at 400A during heat run/PGC RSS.A78B1 on 18th of February @ 02:19:26 at 400A during heat run/PGC RSS.A78B1 on 19th of February @ 01:07:48 at ~335A during heat run/PGC At first sight -> Looking like (and being mistakenly classified as) a quench, if not… Looking familiar?

  3. .. another one @ flat top…

  4. ..while ramping…

  5. Cross-talk @ 400A • During heat runs and PGCs, the normal cross-talk can be observed (different to RCO.A45B1..)

  6. How to diagnose… • Although not always as clearly visible, V_MEAS is a better signal to observe, suggesting sudden changes of impedance • With the loosening of the connection, also the I_ERR_MA significantly increases, mostly well before the circuit trip 1 min

  7. Similar on the flat top…

  8. …and the guilty one is… • Following the repetitive trips, EPC proceeded to exchange the power module and found… • …a loose bolt on the DCCT head, right next to the thyristor… • Note: EPC verified that even without the tightening bolt the circuit can NEVER completely open

  9. How to detect other case? • Are similar cases possible in the machine -> Certainly YES • Can we detect them? YES, but needs special runs (few hours for the whole machine)… • The slower the loop is, the worse the rejection of perturbations will be • By putting all loops slower than usual (10 or 100 times), and running the circuit in DC state (80% of nominal current) one should be able to detect bad connection through verification of the I.ERROR (to be confirmed for circuits with >> time constants). 0.1V

  10. Thanks a lot for your attention 10

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