Download MICE Magnet Readiness Review RAL, June 28 th , 2016

SS QPS
S. Feher
MICE Magnet Readiness Review
RAL, June 28th, 2016
Outline
• Status of SS electrical circuits
• Operational Requirements
• Modified magnet protection scheme and
operation of the Power Supplies
• Conclusions
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Status of SS Electrical Circuit
SSD
• Known Damage:
–
–
–
–
–
LTS lead between the HTS lead and the M1 coil is open
Internal diode pack connection is open for M1
At one side of the M1 LTS lead is shorted to ground
The two LTS leads for M1 are connected to each other; finite resistance
M2 coil is connected to M1 coil therefore connected to ground with ~ 1.3 kΩ
resistance
• Possible Future Degradations:
– M2 ground connection becomes more solid; less resistance
– Physical damage to M2 is worse than we currently believe
– He-to-Vacuum leak occurs at M1/M2 feedthrough (between the cold mass and
insulating vacuum)
SSU
• No Known Issues
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Status of SSD Electrical Circuit
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
R1
LTS/N
R1
R2
Energy
Absorber
LTSc
HTS
LTSa
Internal
Diode
Pack
M1
Internal
Diode
Pack
M2
LTS/N
LTSb
LTSd
Feedthroughs
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
LTS/N
R1
R2
Energy
Absorber
R1
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Operational Requirements
By design:
• Powering
– Current measurement accuracy 2x10-4 (new transductors being
installed)
– Fail safe powering; no harm to equipment (Magnet, leads, PS itself)
and personnel
• Magnet circuit protection
– Coils are self protected; if the coil quenches it is sufficient to turn off the
PS
– HTS and LTS leads during quench: keep the hot spot temperature
below 300 K
– Coils hot spot temperature during quench less then 120 K
– Magnet peak voltage relative to ground below 1600 V; for ECE circuit
internal diode pack is needed to fulfill this requirement
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Operational Requirements
Practical reasons:
• Safe cold HV withstand to ground values measured for SSU
and SSD were ~ 150 V ( breaks down ~ 200 V)
– Localized at the feedthrough (air-to-vacuum) region
• HTS lead voltage less than 3 mV
– QPS HTS lead quench detection threshold value is set at 1 mV
• Keep the LTS lead voltages during quench as low as possible
– Apply low detection threshold values to keep the hot spot temperature
as low as possible
•
June 28, 2016
No clear understanding (as built) what are the lead dimensions and/or cooling
conditions, consequently quench integral value limits are not known.
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
QP Modifications
• Existing QPS was reconfigured:
– Introduced dI/dt signals for all the magnet currents
• Every magnet current is measured with transductors
• The dI/dt signal is obtained with digital signal processing of the magnet current
signal
– Quench detection of the M1 and M2 magnets are using
Wcoil – const * dI/dt signals with low threshold values; the goal is to
be at least less than 100 mV
• Separate protection processor is used for LTS and HTS
leads/magnet circuit
– Second FPGA card provides additional trigger to open the external
diode packs for each magnet circuit separately
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Coil Protection
SSU
• M1 and M2 is using Wcoil – const * dI/dt signals
• E1-C-E2 is using Half – Half bucked half coil signals
SSD
• M2 is using Wcoil – const * dI/dt signals
• E1-C-E2 is using Half – Half bucked half coil signals
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
PS system Modifications
• Redundant contactors were implemented for the main
switches that open when quench is detected
• External diode packs, dump resistors and additional
contactors were procured and installed
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
END
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Protection Issues
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
LTS/N
Internal
Diode
Pack
Feedthroughs
R1
R2
Energy
Absorber
R1
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
• Direct protection of LTSa and LTSb segments with V-taps
• LTSd is only protected with the magnet; low threshold settings are required
to lower the hot spot temperature
• LTS/N easily can be overheated
• Internal diode/resistor pack does not extract enough energy
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Proposed Operational Configuration
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
LTS/N
Internal
Diode
Pack
Feedthroughs
R1
R2
Energy
Absorber
R1
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
• Carefully selected External diode pack (M1 and M2 ~ 5 V, for
ECE ~ 10 V), and R2 (0.5 Ω)
• Contactor for the External diode pack is open; not to interfere
with PS operation
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Different Quench and Failure Scenarios
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
LTS/N
Internal
Diode
Pack
Feedthroughs
R1
R2
Energy
Absorber
R1
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
1.
2.
3.
4.
5.
6.
Magnet quench
HTS lead quench
LTSa or LTSb quench
LTSd quench
Ground fault
PS malfunction
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Magnet Quench
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
R1
LTS/N
Internal
Diode
Pack
Feedthroughs
R1
R2
Energy
Absorber
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
•
Magnet quench is detected
•
•
•
•
During magnet quench HTS or LTSa or LTSb quench occurs
•
•
•
PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE
External diode pack contactors close
Diode Pack is sized to keep the internal diode pack open (M1 and M2 ~ 5 V,
for ECE ~ 10 V); current is circulated through the external diode pack
External diode pack contactor opens for the particular circuit
R2 resistor is sized (0.5 Ω) to keep the max voltage below 150 V in a case LTSc or LTS/N
opens
Ground fault occurs during quench
•
June 28, 2016
No additional action – no influence on maximum external voltage
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
HTS or LTSa or LTSb Quenches
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
R1
LTS/N
Internal
Diode
Pack
Feedthroughs
R1
R2
Energy
Absorber
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
•
HTS or LTSa or LTSb quench is detected
•
•
•
•
During HTS or LTSa or LTSb quench the magnet also quenches
•
•
PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE
External diode pack contactor remain open for the quenching circuit the rest of them will
be closed – this requires major modifications of the QPS; more channels needed
R2 resistor is sized to keep the max voltage below 150 V in case LTSc or LTS/N opens
No additional action – the current decay will be faster
Ground fault occurs during quench
•
June 28, 2016
No additional action – no influence on maximum external voltage
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
LTSd Quenches
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
LTS/N
Internal
Diode
Pack
Feedthroughs
R1
R2
Energy
Absorber
R1
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
•
LTSd quench is detected
•
•
•
•
During LTSd quench the magnet also quenches
•
•
This quench can not be separated from a magnet quench – very low quench detection threshold
is required; dI/dt based quench detection system for M1 & M2 and significantly lower threshold
for the ECE half coil based detection system (more filtering) are needed
PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE
External diode pack contactor remain open for the quenching circuit the rest of them will be
closed – R2 resistor is sized to keep the max voltage below 150 V in case LTSc or LTS/N opens
No additional action – the current decay will be faster
Ground fault occurs during quench
•
June 28, 2016
No additional action – no influence on the maximum external voltage
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Ground Fault or PS Malfunction
Cold Mass Shell
LTSd
HTS
LTSa LTSb
LTSc
External
Diode
Pack
PSU
LTS/N
Internal
Diode
Pack
Feedthroughs
R1
R2
Energy
Absorber
R1
LTSc
HTS
LTSa
LTS/N
LTSb
LTSd
Vacuum Shell
•
Ground fault or PS malfunction
•
•
•
•
PS Contactors open for all circuits: M1 (for SSD M1 is floating), M2, ECE
External diode pack contactors close
Diode Pack is sized to keep the internal diode pack closed (M1 and M2 ~ 5 V,
for ECE ~ 10 V); current is circulated through the external diode pack
During ground fault or PS malfunction HTS or LTSa or LTSb or LTSd quench occurs
•
•
June 28, 2016
External diode pack contactor opens for the particular circuit
R2 resistor is sized (0.5 Ω) to keep the max voltage below 150 V in a case LTSc or LTS/N
opens
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
New SSD QPS Configuration
For the newly designed SSD cold mass we will implement
several changes:
– Every coil will have two center V-taps (one primary and one redundant)
•
All coils detection circuit will utilize Half Coil 1 – Half coil 2 signal with low threshold
values
– There will be separate V-taps for the LTS and HTS segments
•
At every V-tap locations will be two V-taps (one primary and one redundant)
– External dump system will be used
•
Dump resistor will be adjusted to the HV withstand values
– Every coil will have two heaters (one primary and one redundant)
•
Once LTS, HTS or magnet quench is detected the heaters will be energized to
initiate a magnet quench
– For ground fault and PS failure cases slow ramp down will be initiated
•
June 28, 2016
External diode pack will be used
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)
Conclusions
• The proposed PS and QPS configuration will
minimize the risk of loosing the magnet circuits
• Requires major modifications of the QPS
June 28, 2016
Sandor Feher | MICE Magnet Rediness Review (Ral, June 28, 2016)