DFLAS (60 mV at I nom )

Arjan Verweij, CERN, AT-MCS, 27/2/2007

DFLAS (60 mV at Inom)

DFLAS

DFLAS

DFLAS

77xMB (7.85 H,~ 150-450 nΩ)

DQRB (75 mΩ)

Pt 8

Pt 7

gnd

RPTE (16250 A)

Circuit RB.A78

DQ

RB

(75

mΩ

)

DQSB

I_min=350 AI_inj=760AI_nom=11850 AStored energy at I_nom=1.22 GJ

77xMB (7.85 H,~ 150-450 nΩ)

1 Ω

DCCT

Signals:Vcircuit

VDCCT

Vlead (HTS and resistive)Vdump

Rw

Rint


V-taps MBV-taps MB

A1

A2

V1

V3

V2

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

100

heater

Additional V-taps on busbars ??

I

term. A

term. B

14 15

12 13

112

111

119

211

113

219213 212


ResistancesResistances

PC: RPC: Rintint=0.9 m=0.9 m

Warm cables: RWarm cables: Rww ≈≈ 1 m 1 m

Cold joints in MB’s: 154x9x(0.4Cold joints in MB’s: 154x9x(0.4±±0.2) n0.2) n ≈≈ 280-830 n 280-830 n

Cold joints in busbars: about 154x2x0.2 nCold joints in busbars: about 154x2x0.2 n ≈ ≈ 60 n60 n

Leads (at ILeads (at Inomnom): 4x0.06 V / 13000 A ): 4x0.06 V / 13000 A ≈≈ 18 18

Dump resistances: 2x75 = 150 mDump resistances: 2x75 = 150 m

NB: MB’s at 300 K: 154x5.7 NB: MB’s at 300 K: 154x5.7 = 880 = 880


PICPC current loop parameters close to 15.7 H, 1 m

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: I= 0.012 mA, V50 Hz=60 mV , V300 Hz=350 mV )

Vthreshold (target: 100 mV)

EMC ?

Analysis of Rjoints (exp: 350-900 n)

2. EE discharge without quench (760, 2000, 6000, 8500, 12000 A)

(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/ = 0.75 V)

Quenchback ?

AnalysisAnalysis


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


Natural quenchNatural quenchFind out quench origin (MB??, busbar, etc)Find out quench origin (MB??, busbar, etc)Analyse quench:Analyse quench:

- Delay for Q detection- Delay for Q detection

- Delay for heater firing- Delay for heater firing

- Delay for start SC-n transition (induced by heaters)- Delay for start SC-n transition (induced by heaters)

- Delay for diode conduction- Delay for diode conduction

- Delay for PC abort and switch- Delay for PC abort and switch

- Compare V- Compare VMBMB(t) and I(t) and IPCPC(t) to calculated/expected R(t) to calculated/expected RMBMB(t) and I(t) and IMBMB(t) behaviour,(t) behaviour,

- Compare Q data with SM18 tests (in case of MB quench).- 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!!!Analysis should give an answer if it is safe to power the circuit again!!!


RemarksRemarks

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 n. 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.


LinksLinks

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

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Jeumont

Ansaldo

BNN

DFLAS (60 mV at I nom )

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