Transcript Alstom: 01B

Rint
Circuit RB.A78
DCCT
RPTE (16250 A)
gnd
1Ω
Rw
DFLAS
DQRB (75 mΩ)

Pt 8
DQSB
DFLAS (60 mV at Inom)
77xMB (7.85 H,
~ 150-450 nΩ)
77xMB (7.85 H,
~ 150-450 nΩ)
DFLAS
DFLAS
DQRB (75 mΩ)
Pt 7
Arjan Verweij, CERN, AT-MCS, 27/2/2007
I_min=350 A
I_inj=760A
I_nom=11850 A
Stored energy at I_nom=1.22 GJ
Signals:
Vcircuit
VDCCT
Vlead (HTS and resistive)
Vdump
V-taps MB
V1
213
212
219
heater
A2
term. A
211
V2
100 W
113
term. B
14
15
V3
I
12
A1
112
111
119
13
Additional V-taps on busbars ??
QPS: Differential (V3-V2) – (V2-V1), threshold: 100 mV, 10 ms
Stored signals: V1, V2, V3 during 10 sec before and 300 sec after quench, f=200 Hz
Arjan Verweij, CERN, AT-MCS, 27/2/2007
Resistances
PC: Rint=0.9 mW
Warm cables: Rw ≈ 1 mW
Cold joints in MB’s: 154x9x(0.4±0.2) nW ≈ 280-830 nW
Cold joints in busbars: about 154x2x0.2 nW ≈ 60 nW
Leads (at Inom): 4x0.06 V / 13000 A ≈ 18 mW
Dump resistances: 2x75 = 150 mW
NB: MB’s at 300 K: 154x5.7 W = 880 W
Arjan Verweij, CERN, AT-MCS, 27/2/2007
Analysis
PIC
PC current loop parameters close to 15.7 H, 1 mW
PLI-1 (760 A), PLI-2 (2000 A), PLI-3 (6000 A), PLI-4 (8500 A), PNO (12000 A)
1. Current loop stability (760, 2000, 6000, 12000 A)
Vnoise (freq, ampl) on voltages for Q detection (Vdiff) and logging (VMB)
(exp. for full circuit: DI= 0.012 mA, DV50 Hz=60 mV , DV300 Hz=350 mV )
Vthreshold (target: 100 mV)
EMC ?
Analysis of SRjoints (exp: 350-900 nW)
2. EE discharge without quench (760, 2000, 6000, 8500, 12000 A)
t (exp: 15.7/0.151 = 104.0 sec)
Vmax over dump resistance (exp: I * Rdump = 57 V)
Vmax in circuit (exp: 0.25 * I * Rdump =14.2 V)
Vmax over MB (exp: 0.102 H * I/t = 0.75 V)
Quenchback ?
Arjan Verweij, CERN, AT-MCS, 27/2/2007
3. Heater firing (select several magnets) (760, 2000, 6000, 12000 A)
Q detection delay (exp: ??)
Heater energy (exp: ??)
Analyse VMB(t) and deduce RMB(t) and IMB(t)
Analyse signal of quenched magnet for possible V oscillation. If present then ....
Verify possible quenching of other magnets through:
- erratic quench signal
- quench back
Verify possible quenching of busbar cable next to quenched magnet(s)
4. Current leads (760, 2000, 6000, 8500, 12000 A)
Voltage over lead (exp: 60 mV)
Temperatures at top and bottom of the lead
Arjan Verweij, CERN, AT-MCS, 27/2/2007
Natural quench
Find out quench origin (MB??, busbar, etc)
Analyse quench:
- Delay for Q detection
- Delay for heater firing
- Delay for start SC-n transition (induced by heaters)
- Delay for diode conduction
- Delay for PC abort and switch
- Compare VMB(t) and IPC(t) to calculated/expected RMB(t) and IMB(t) behaviour,
- Compare Q data with SM18 tests (in case of MB quench).
Verify possible quenching of busbar cable next to quenched magnet(s),
Analyse signal of quenched magnet for possible V oscillation. If present then:
- detect if all diodes are still OK
- perform HV test
- connect 1 MHz data acq. system to sick magnet
- perform quenches at reduced current
Analysis should give an answer if it is safe to power the circuit again!!!
Arjan Verweij, CERN, AT-MCS, 27/2/2007
Remarks
It is not sure if voltage oscillation (of a ‘sick’ magnet can be seen using a sampling frequency of
200 Hz.
A heater test at 760 A will probably not quench the magnet. No tests are made in SM18 at this
current level.
The total resistance of all (about 1700) splices in the circuit is rather unknown. I expect a value
between 350 and 900 nW. We should try to deduce this value by measuring the voltage
over all the magnets at several DC current levels (e.g. during the ‘current loop stability’
tests). The accuracy of this measurement is not known due to PC noise, voltage pick-up
noise, and possible current redistribution effects. It should be tried to give at least an upper
limit for the total resistance.
Arjan Verweij, CERN, AT-MCS, 27/2/2007
Links
EDMS 249359: Electrical connections of the LHC main dipoles
LHCMBB_A0003: Instrumentation drawings voltage taps MBB
LHC power converters, F. Bordry, Chamonix XI
Results splice measurements FRESCA
0.8
Splice resistance [nOhm]
0.7
Jeumont
Ansaldo
BNN
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
10
12
14
16
18
20
Arjan Verweij, CERN, AT-MCS, 27/2/2007