Download Proposal_for_measurements_on_RB

Proposal for measurements on
RB.A81 on 1st September 2010
Emmanuele Ravaioli
Thanks to A. Verweij
25 August 2010
QSO signals: Difference between magnet voltages
I_max = 2 kA; dI/dt = 10 A/s; Sector 12; 10-05-2010 22.08
Magnet 001  Blue
Magnet 154  Red
Power converter
shut down
First
switch opening
Emmanuele Ravaioli
Second
switch opening
2
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.
Emmanuele Ravaioli
3
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.
Emmanuele Ravaioli
4
Oscilloscope connections
(PS: the scopes will be insulated from the 220 V mains)
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
PC shut down
-200 ms – 800 ms
500 kHz
500 000
PC shut down
-200 ms – 800 ms
500 kHz
500 000
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
U1 and U2 of
magnet 41
U1 and U2 of
magnet 42
U1 and U2 of
magnet 115
Electrical numbering Top assembly name
Assembly name
Distance from IP1.L1
Relative distance
~ 38 m from #42
Magnet 41
LBBLA.33L1
MB.B33L1
-1586.2207 m
Magnet 42
LBBLA.32L1
MB.C32L1
-1548.4307 m
Magnet 115
LBALA.34L1
MB.B34L1
-1639.6707 m
Emmanuele Ravaioli
~ 53 m from #41
5
Magnet choice
The 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.
Emmanuele Ravaioli
6
Schedule
The 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, ….?
Emmanuele Ravaioli
7
Emmanuele Ravaioli
8
Max U_QSO during PC shut down – 2 kA
The PSpice model simulates well only the behavior of the ‘normal magnets’
Emmanuele Ravaioli
9
Max U_QSO during PC shut down – 6 kA
The PSpice model simulates well only the behavior of the ‘normal magnets’
Emmanuele Ravaioli
10