Q5R4 corrector shorted to ground. Ongoing investigation
description
Transcript of Q5R4 corrector shorted to ground. Ongoing investigation
![Page 1: Q5R4 corrector shorted to ground. Ongoing investigation](https://reader036.fdocuments.in/reader036/viewer/2022062322/56814bf5550346895db8e917/html5/thumbnails/1.jpg)
AT
-ME
L G
roup
Mee
ting
, C
ER
N,
1211
Gen
eva
23
1
Q5R4 corrector shorted to ground. Ongoing investigation
Status at 18 June 2007
N. Catalan Lasheras
![Page 2: Q5R4 corrector shorted to ground. Ongoing investigation](https://reader036.fdocuments.in/reader036/viewer/2022062322/56814bf5550346895db8e917/html5/thumbnails/2.jpg)
AT
-ME
L G
roup
Mee
ting
, C
ER
N,
1211
Gen
eva
23
2
History of Q5R4
No electrical NC during manufacturing
Electrical insulation tests done in SMI2 on 24/07/06 includes MCBY to MQY, Quench Heaters, ground, and each other.
– Results ok (EDMS 759062)
Installed in the tunnel on 2 August 2006
Major movements of the D4-Q5 magnets and supports in 4R (NC 833372)
– Q5 moved 9 mm under vacuum. Came back to 6 mm in atmospheric pressure
– Interconnection open to check PIM. Ok. Closed again.
– Re-test in vacuum foreseen. (?)
HV breakdown on circuit RCBYH5.R4B2 during ELQA at warm (NC 842369)
![Page 3: Q5R4 corrector shorted to ground. Ongoing investigation](https://reader036.fdocuments.in/reader036/viewer/2022062322/56814bf5550346895db8e917/html5/thumbnails/3.jpg)
AT
-ME
L G
roup
Mee
ting
, C
ER
N,
1211
Gen
eva
23
3
MCB corrector short-circuited in Q5R4, EDMS 842369V. Chareyre
A discharge occurred during the electrical insulation test (voltage level at warm, 300 V)
Resistance to ground around 180 Ω (before pressure test in sector 45)After the pressure test, the problem has been deteriorated: around 2 Ω
A current of 70 mA is impressed in the circuit
Voltage drops across voltage-taps are measured, ground is used as a voltage pick-up
Short localized between the cold v-tap B and the coil BUT the v-tap is very close to the coil
The problem may be at the level of the connection of the coil
DFLES.5R4.1
DFLES.5R4.2
Current lead
Bus-bar, L~ 5.6 m
+ 3.758 mV
+ 3.753 mV
+ 35.8 V
+ 3.753 mV
+ 0.33 mV
I
V-tap Cold v-tap A
V-tapCold V-tap B
A
B
Voltage pick-upConnection bus-bar to coil
![Page 4: Q5R4 corrector shorted to ground. Ongoing investigation](https://reader036.fdocuments.in/reader036/viewer/2022062322/56814bf5550346895db8e917/html5/thumbnails/4.jpg)
AT
-ME
L G
roup
Mee
ting
, C
ER
N,
1211
Gen
eva
23
4
Measure repeated after the pressure test. R. Mompo
A third test confirmed that the short is on the lead side and not inside the corrector.
Voltage measurement performed from the IFS box on connector P25:Polarity 1:
EE871 Voltage, resistive lead ext A warm V-tapEE811 Voltage, dipole orbit ext A V-tapEE812 Voltage, dipole orbit ext B V-tapEE872 Voltage, resistive lead ext B warm V-tap
Results of the continuity test: I= 0.03 A
Polarity 1:
EE871 15.36 VEE811 15.36 VEE812 2.00 mVEE872 0.39 mV
Polarity 2 Inversed polarity of DC PS and multimeter reference
EE871 0.299 VEE811 1.93 VEE812 15.57 mVEE872 15.53 mV
Polarity 1 vs Ground
EE871 15.63 V EE871 15.64 VEE811 15.63 V EE811 15.64 VEE812 0.03 mV EE812 0.025 mVEE872 -1.60 mV EE872 -1.61 mV
Polarity 2 vs GroundUsing another ground reference
EE871 -15.56 mV EE871 -15.57 mVEE811 -15.56 mV EE811 -15.57 mVEE812 -0.078 mV EE812 -0.070 mVEE872 1.55 mV EE872 1.57 mV
Investigation carried out on 24/05/2007 on circuit RCBYH5.R4B2 related to NC 842369: Sketch
Ground taken at the level of the cover flange
P25
![Page 5: Q5R4 corrector shorted to ground. Ongoing investigation](https://reader036.fdocuments.in/reader036/viewer/2022062322/56814bf5550346895db8e917/html5/thumbnails/5.jpg)
AT
-ME
L G
roup
Mee
ting
, C
ER
N,
1211
Gen
eva
23
5
What could have gone wrong?
Bus-bar of D4 and corrector very close.
They may have been put in contact after stretching D4 bus bar during the vacuum test.
![Page 6: Q5R4 corrector shorted to ground. Ongoing investigation](https://reader036.fdocuments.in/reader036/viewer/2022062322/56814bf5550346895db8e917/html5/thumbnails/6.jpg)
AT
-ME
L G
roup
Mee
ting
, C
ER
N,
1211
Gen
eva
23
6
What to do?
According to the optics database not used for optics. Only orbit correction.
Proposal:
Measure short after cool-down.
– Monitoring the movement of the cold mass and the short could be a possibility
Open the interconnect after warm-up. Use and endoscope to check/confirm the contact
In the worst case a repair in situ seems feasible.
– Insert extra insulation
– Open the cold mass cylinder and repair connections