Proposal for measurements on RB.A81 on 1st September 2010

25 August 2010

Emmanuele Ravaioli

Thanks to A. Verweij

QSO signals: Difference between magnet voltagesI_max = 2 kA; dI/dt = 10 A/s; Sector 12; 10-05-2010 22.08

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Magnet 001 BlueMagnet 154 Red

Emmanuele Ravaioli

Power converter shut down

Firstswitch opening

Secondswitch opening

Main goals of the measurements (1)1. Understanding the behavior of the circuit during the power-converter shut

down, with particular attention to the oscillations of the aperture voltages, and their difference.

In each sector, about 60% of the dipoles present an unexpected behavior: during the PC shut-down, U_QSO reaches values ~5 times larger than the other magnets and than the values calculated by PSpice.

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Main goals of the measurements (2)2. Assessing the voltage across the switches (and to compare them later on

once the snubber capacitors are installed).Possibly to upgrade the current switch model in PSpice.

The proposed oscilloscope measurements are required because the oldQPS and newQPS have a sampling frequency that is too low (200 Hz and ~1 kHz) to properly analyse the transitory.It is important to understand the unexpected behavior of U_QSO, since this issue concerns about 60% of the magnets and the analysis of the present data shows that it is not related with the electrical or physical position of the magnets, nor with the magnet and cable manufacturers, nor with the chronology of installation.

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Oscilloscope connections(PS: the scopes will be insulated from the 220 V mains)

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Electrical numbering Top assembly name Assembly name Distance from IP1.L1 Relative distance

Magnet 41 LBBLA.33L1 MB.B33L1 -1586.2207 m ~ 38 m from #42

Magnet 42 LBBLA.32L1 MB.C32L1 -1548.4307 m

Magnet 115 LBALA.34L1 MB.B34L1 -1639.6707 m ~ 53 m from #41

Oscilloscope measuring: Triggering event Time frame

( t=0 at triggering event)Frequency of acquisition

Number of points (internal memory)

Vout of PC PC shut down -200 ms – 800 ms 5 kHz 5 000

U1 and U2 of magnet 41 PC shut down -200 ms – 800 ms 500 kHz 500 000

U1 and U2 of magnet 42 PC shut down -200 ms – 800 ms 500 kHz 500 000

U1 and U2 of magnet 115 PC shut down -200 ms – 800 ms 500 kHz 500 000

U_RES switch pt1 1st switch opening -1 ms – 19 ms 1 MHz 20 000

U_RES switch pt8 2nd switch opening -1 ms – 19 ms 1 MHz 20 000

Magnet choiceThe three magnets have been selected based on the behavior they showed during past tests: Magnets 42 and 115 showed a U_QSO signal during the PC shut-down transitory at 2 kA bigger than that at 6 kA.Magnet 41 showed a regular behavior, but has been selected to highlight the difference as compared to the other two magnets. Besides, the three magnets are physically close each other, and this will simplify the operations and reduce the number of the required insulator transformers.

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ScheduleThe measurements are scheduled for the night shift between 1st and 2nd September 2010, starting at 18.00 .Four tests will be launched; in each test, the current of the circuit will be raised with a dI/dt = 10 A/s. When I_max is reached (while the current is still raising), the power converter will be shut down (triggered by the QPS); after 350 ms, the first switch (pt1, middle of the chain) will be opened; after another 250 ms, the second switch (pt8, close to the power converter) will be opened as well.The values of I_max in the four tests are: 1 kA, 2 kA, 4 kA, 6 kA (actually a bit below 6 kA, because the PC slows down at the end of the ramp).If there is sufficient time possibly also tests with I_max = 3 kA and 5 kA can be performed. Another set of tests with dI/dt = 0 A/s (no ramping up) would also be interesting, at the same current levels; since the test at 6 kA requires a long standbye-period due the cooling of the dump resistors, it will be probably skipped.

The following persons will be present: Knud Dahlerup-Petersen; Hugues Thiesen; Arjan Verweij; Bozhidar Ivanov Panev; Mike Koratzinos; Emmanuele Ravaioli; Zinur Chariffouline, ….?

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Max U_QSO during PC shut down – 2 kA

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The PSpice model simulates well only the behavior of the ‘normal magnets’

Max U_QSO during PC shut down – 6 kA

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The PSpice model simulates well only the behavior of the ‘normal magnets’