CSCM type test:Diode Leads and Diodes

Gerard Willering & Vincent RogerTE-MSC

With thanks to Bernhard Auchmann, Zinour Charifoulline, Scott Rowan, Arjan Verweij, Daniel Wollmann

and all involved in the CSCM test.

12-06-2013 - MPE-TM

Outline

• Diode leads• Test parameters and conditions• Measurements• Comparison with test station data

• Diodes• Test parameters and conditions• Measurements

• Concluding remarks

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Diode leads: Measured voltages

Board A

Board B

Large data set acquired:RB 156 voltage signalsRQF 51 voltage signals

QPS Board A: BB + interconnectionsQPS Board B: BB + interconnections + diode leads

Diode lead resistance

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Diode leads

Include 3 types of contact- Diode – Heatsink (clamped)- Heatsink – busbar (bolted)- Busbar – busbar (bolted)- About 60 cm of bus bar

In total 6 contacts per voltage signal.

Diode lead resistance

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Low-resistance RB lead

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60

80

100

0 5 10 15 20 25 30 35 40

Resi

stan

ce (u

Ohm

)

Time (s)

DCBD.7R2.L 2 kA4 kA4 kA6 kA7 kA8 kA7 kA9 kA6 kAI-profile

Diode lead resistance

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Highest resistance RB lead- At 2 kA run still low resistance- Resistance increase from the first 4 kA run onwards- Resistance reduction during long 7 kA run after short 8 kA run.

- Low-current characteristics used for statistical analysis.

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0 50 100 150 200 250 300

Resi

stan

ce (u

Ohm

)

Consecutive runs (time in seconds)

DCBA.A16R2.R 2 kA

4 kA

4 kA

6 kA

7 kA

8 kA

7 kA

9 kA

6 kA

low current resistance

2 kA4 kA

4 kA

6 kA 7 kA

8 kA 9 kA 6 kA

7 kA

Typical behavior: 1. At the first ramp to a higher current

the resistance increase is significant

2. After a prolonged run at the similar current the resistance is reduced.

For the RQF diode leads similar behavior is seen.

-20

-10

0

10

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30

40

50

2 kA 4 kA 4 kA 6 kA 7 kA 8 kA 7 kA 9 kA first to last run

Resi

stan

ce (u

Ohm

)

Run

Low current resistance affected by each runRB

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60

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80

90

100

0 50 100 150 200 250 300

Resis

tanc

e (u

Ohm

)

Consecutive runs (time in seconds)

DCBA.A16R2.R 2 kA

4 kA

4 kA

6 kA

7 kA

8 kA

7 kA

9 kA

6 kA

low current resistance

2 kA4 kA

4 kA

6 kA 7 kA

8 kA 9 kA 6 kA

7 kA

During CSCMRmax = 70 µΩ in 6 contacts combined

In Block-4Rmax > 35 µΩ in 1 diode-heatsink contact.

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5

10

15

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35

40

0 200 400 600 800 1000 1200

Resi

stan

ce (μ

Ω)

Time of consecutive runs (time in ms)

Test station measurement Block4 - MDA 0790 - Heatsink to diode resistance

1.3 kA

5 kA 10 kA

13 kA 13 kA

8 more runs at13 kA

100 mV DAQ saturation:35 microOhm is reached at least!

Note: - Different current profiles- Different cooling

Diode lead resistance - Comparison to test station data

?

Fast jumps in diode lead resistanceFast jumps identified as the main risk: possibly mechanical movement in bolted joints

Where Type I (kA)

Step (mv)

Step (μΩ)

Time (ms)

LHC ’11 Quad lead 4 160 40 <50

LHC ‘13 Dip lead 4 30 7 < 120

LHC ’13 Quad lead 4 50 12 < 120

LHC ’13 Quad Lead 6 50 8 < 120

LHC ‘13 Quad lead 6 24+18 4+3 < 120

SM18 HS-diode 13 65 5 50

0

2000

4000

6000

8000

10000

12000

14000

0

5

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25

30

0 10 20 30 40 50 60

Curr

ent (

A)

Resi

stan

ce (μ

Ω)

Time (s)

1st test at 13kA

2nd test at 13kA

3rd test at 13kA

4th test at 13kA

5th test at 13kA

6th test at 13kA

7th test at 13kA

8th test at 13kA

9th test at 13kA

10th test at 13kA

Current

2011 – LHC quad - Verweij

2013 – CSCM type test

2012 – SM18 test station Heatsink-busbar

The SM18 test shows that heatsink-busbar contacts can have fast jumps.

Remarks on Diode lead resistance

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Data analysis- Maximum resistance is in the range as observed for diode-heatsink contact- Fast jumps may occur as well in diode-heatsink contact- A resistance increase in the other two contacts are not identified, but cannot

be excluded.- The high-resistances are all “self-healing” as was seen before for diode-

heatsink contacts

Impact on the test after LS1- No unexpected results → No show stoppers.

Note: the part that was deemed most risky is consolidated during LS1 (the connection plates of the quad diode leads).

Diode opening

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Prior to high current runs the diodes need to be opened.

1. PC initialization

2. Ramp to 400 A

3. Warmup of magnets and gradual opening of diodes

4. Warmup of diodes → reduction of Vforward

5. High current ramp

In stage 1 and 2 most current is in the magnetFrom stage 3 on the current shifts more to the diode circuit.

“Slow” opening is required to allow the PC to respond.

Diode opening – Forward voltage

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

0

0.5

1

1.5

2

2.5

3

0 20 40 60 80 100 120 140 160 180 200

Volta

ge (V

)

Time (s)

DQQDS.B10L3.RQF.A23 Run 1 - 900A

Run 2 - 2kA

Run 3 - 4kA

Run 4 - 6kA

Run 5 - 6kA

run 6a - 400A

Run 6b - 8kA

0

0.5

1

1.5

2

2.5

3

0 20 40 60 80 100 120 140 160 180 200

Volta

ge (V

)

Time (s)

DQQDS.B11L3.RQF.A23 Run 1 - 900A

Run 2 - 2kA

Run 3 - 4kA

Run 4 - 6kA

Run 5 - 6kA

run 6a - 400A

Run 6b - 8kAvariation less than 10 mV

Dip in voltage just after opening

Typical opening1. Increase in Imagnet and V

2. Vforward reached

3. Warming of the diode – decrease in Vforward

1

2

3

Dip in voltage after opening- Only in Quad diodes at I = 400 A in 47 out

of 364 cases.- Quick decrease in voltage suggest quick

increase in temperature → local warm-spot- Regular pattern, always 1.55 to 1.65 V- At 1.5 V the temperature is well below 70 K.

- In all the cases the voltage characteristics is the same within ± 1 % and the dip seems to have no permanent effect.

Remarks on Vforward of the diodes

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

Data analysis- Strange dip seen only in 13 % of Quad diode openings- At high currents these diodes did not show any deviation from normal behavior.

Comments for LS1 qualification test- Since Vforward remains at 1.6 V the temperature is much less than 70 K. - After the dip all diodes show similar values of Vforward .

Concluding remarks on diodes and diode leads

Gerard Willering – TE-MSC-TF - CSCM type test - 16/05/2013

- No show stoppers identified on diodes and diode leads for the CSCM test in LS1

- Large sets of data on diode leads show resistance variations in the range that has been seen before.

- Variations in diode opening voltage were unexpected, but are deemed not to be a risk for the test.

Spare slides

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2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4

Num

ber o

f eve

nts

Maximum voltage during opening (V)

With dip in voltage

Without dip in voltage

RQF - total events 364 (7 runs with 52 diodes)

Diode opening – statistics of dips

With a lower opening temperature (higher voltage) the dip is occurring more often.

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0 500 1000 1500 2000 2500

Res

ista

nce

(u

Oh

m)

and

Cu

rren

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A)

Time (s)

Diode-heatsink MDA1267-A

Increasing to 6 kA Increasing in to 13 kA

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2 kA 4 kA 6 kA 6 kA first to last run

Resi

stan

ce (u

Ohm

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Run

change in low current affected by each runRQF

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-10

0

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30

40

50

2 kA 4 kA 4 kA 6 kA 7 kA 8 kA 7 kA 9 kA first to last run

Resi

stan

ce (u

Ohm

)

Run

Low current resistance affected by each runRB