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Published byBrett Pierce Modified over 9 years ago
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11.12.2003AB-CO TC / J. Wenninger1 MCB orbit correctors There are 752 MCBH(V) SSS orbit corrector circuits. Individually powered by a ± 60 A, ± 8 V converter. PCs installed in the tunnel (radiation). PCs are in production today. The design MTBF is 100’000 hours 1 failure in operation every 100 hours. Assuming ½ MCBs have significant kicks, we may get 1 MCB- induced beam loss per week due to our orbit tight tolerances !
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11.12.2003AB-CO TC / J. Wenninger2 Crowbar In case of PC failure the magnet is shorted and discharged through a crowbar. Time constants : without crowbar85-130 seconds with crowbar 30-35 seconds - mostly due to 100 m resistors
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11.12.2003AB-CO TC / J. Wenninger3 Remedies The orbit FB could save the beam : The FB must switch in a compensating scheme based on nearby correctors (or equivalent) reduce effect to a local bump. The FB must be informed rapidly – time scale of 1 second or less. The circuit time constants should be as long as possible. With the 2 crowbar resistors the situation is very tight… From MP point of view, the MCBs are slow enough even with crowbar resistors not to present a major problem. But the slow is beautiful for MP slower is better !
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11.12.2003AB-CO TC / J. Wenninger4 Can we remove 1 or both crowbar resistors ? Meeting with all concerned parties (AB & AT) : The crowbar resistors have no role in protecting the magnets. The magnets are self-protected. Motivation behind resistors seems to be a shorter circuit discharge time. PC tests performed without crowbar resistors by AB/PO indicate that the resistors can be removed. Implications for electrical safety, since it takes then ~ 10 minutes for the current to go from 60 to below 1 A for the slowest elements. need a rapid decision since the PCs are in production. ECR will be prepared this week.
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