1. Power converters for 2GeV injection
LIU-PS
Power converters for 2GeV injection
J.M. CRAVERO
6 July 2018

2. 1 power converter for a septum magnet - SMH42
Power converter needs
1 power converter for a septum magnet - SMH42
1 power converter for ‘under vacuum’ bumper magnet - BSW42
4 power converters for ‘out of vacuum’ bumper magnets – BSW
1 (or 2) power converters for the Low Beta Quadrupole magnets – QLB33-49
Jose Abelleira - ABT
6 July 2018

3. Power converter for SMH42 septum magnet
New septum technology: Eddy current septum instead of direct drive type.
Septum current has to be bipolar to reduce the leakage field and ‘reset’ the magnetic core.
A flat-top on the current shape is not needed for the beam (3µs duration max.) but to insure current precision and magnetic field stabilization (50-100µs).
Basic specifications are given in the document “Specification for the 2GeV PS Proton injection septa” - EDMS (under approval).
Imax
32 000 A
Waveform
full sine
Magnet inductance (magnet coil only)
1.8 µH
Magnet resistance (magnet coil only)
0.1 mΩ
Pulse length (full sine) 2 ms
Minimum flat-top duration (within specification) 50 us
Vmax (secondary)
420 V
Transformer ratio
1 : 12
Imax (primary)
2680
Vmax (primary)
6500
Current precision (w.r.t. flat-top reference)
+/- 500
ppm
+/- 16
Repetition rate
0.9 s
6 July 2018

4. Two options for the SMH42 power converter topology are currently under study:
3rd harmonic + transformer + active filter (same as existing converter but with higher voltage and bipolar current shape)
 Active filter could be linear mode type or switch-mode type but care should be taken with the applied voltage…
New modular topology + transformer + active filter (to allow standardization with ACC-CONS project)
6 July 2018

5. SMH42 current with 3rd harmonic topology and switch-mode active filter
Some improvements are still needed on the current control loops to achieve the required specifications…
6 July 2018

6. Open issues to be addressed in 2016
Topology definition, current and voltage control loops design, etc…
Functional specification to be released.
Electronic crate and boards to be defined.
Precision current measurement system to be validated.
Pulse transformer study.
Integration in the PS tunnel.
Michael Hourican - ABT

7. PS injection bumpers: actual scheme
The different bumper magnet current waveforms must be identical and synchronized to reduce perturbations on the beam.
Today, we have 4 identical bumper magnets (BSW40, 42, 43, 44) powered by identical capacitor discharge converters (capacitor bank values are matched). The maximum discharge current is 6000A (maximum operational value ~ 4000A?) with 1500V charging voltage.
Maurizio Serluca - ABP
6 July 2018

8. PS injection bumpers for 2GeV injection
1 bumper magnet (under vacuum) – BSW42
4 bumper magnets (out of vacuum) – BSW
Basic specifications are given in the document “Specification for the 2GeV PS Proton injection septa” - EDMS (under approval). Intensive discussions about precision and tracking !
The powering of the bumpers is very challenging:
Shorter bumper pulses will minimize the injection losses. The actual bumpers are 1.6ms half sine and we have agreed on 1ms pulse duration  much faster system is needed
the power converters must provide identical current waveform shapes in different magnet types  active regulation is required with high current, bandwith and precision
Jose Abelleira - ABT
BSM42
BSM4x
Imax
22 000
4200 A
Waveform
half sine
Pulse length (half sine) 1 ms
Magnet inductance (magnet coil only)
0.9 55 uH
Magnet resistance (magnet coil only)
0.1 18 mΩ
Vmax (magnet coil) 97
726 V
Current precision (w.r.t. half sine peak reference)
+/- 2000
ppm
+/- 44
+/- 8.4
6 July 2018

9. BSW40,41,43,44 bumper magnets optimization
The new magnet design has been adapted to power converters capabilities.
The best option is to adopt a magnet design with
low inductance and high current.
The adopted parameters are:
Lmagnet = 55uH
Rmagnet = 2.3mΩ
Imax < 4000A ? (to be specified: the lower, the better ! )
Imin = ??? (to be specified)
6 July 2018

10. Power converters for BSW40,41,43,44
The most promising option is to use modified SIRIUS (power converters for BI.BSW) power converters with 2 power modules in parallel.
The regulation is challenging: several options have been studied.
Current Reference (green) [A]
Output Current (blue) [A]
Voltage Reference (green) [V]
Filter Voltage (blue) [V]
Ludovic Horrein - EPC

11. Some improvements are still needed on the control loops but results are encouraging.
Magnet current (zoom) [A]
Current Reference (green) [A]
Output Current (blue) [A]
Magnet current (zoom) [A]
Time [ms]
Time [ms]
Time [ms]
Instantaneous Accuracy [ppm]
Accuracy [ppm]
Reference [A]
Time [ms]
1ms<t<1.214 ms  limitations  delay of 1.5us  error of 4000ppm
Ludovic Horrein - EPC

12. Power converters for BSW42 Same approach can be used for BSW42 with:
4 modules in serie/parallel to allow operation with increased voltage/current,
pulse transformer + diodes (to cancel the negative current) installed in the tunnel,
demagnetizing circuit at the primary side of the pulse transformer.
To be studied with more details…
SIRIUS converter with
4 modules serie/parallel
Michael Hourican - ABT

13. Open issues for 2016
Specifications of the power converters have to be finalized ! (max./min. operational currents, out of vacuum magnet parameters have to be confirmed, margins ? , etc…) in order to release the functional specifications of the converters.
Proposed converter topologies have to be validated with a prototype,
Control loops / electronics boards have to be further improved to cope with specifications,
Requirements for the control board(s) have to be evaluated (PWM precision, PWM synchronization with external trigger, sampling frequency, delays, etc…)

14. Power converters Low Beta Quadrupoles
The best option is to power the 2 magnets (QLB33-49) in serie (to be confirmed by Maurizio & Dominique) to avoid any tracking issue.
Power converter specifications have to be further investigated.
Modified Maxidiscap converters are targeted for this application.
Open issues for 2016
Specifications of the power converters have to be finalized ! (max./min. operational currents, magnet parameters have to be confirmed (voltage), margins ? , etc…) in order to release the functional specification of the converter,
Flat-top on the magnet current waveform is possible or needed (precision) ?
Imax
200 ? A
Imin ?
Waveform
half sine
Magnet inductance (2 magnets in serie)
2.1 mH
Magnet resistance (2 magnets in serie) 60 mΩ
Pulse length (half sine) 2 ms
Vmax
650 V
Current precision (w.r.t. peak current reference)
???
ppm
Magnet Current [A]
Time [ms]

15. Several specifications/operational requirements are urgently needed.
Conclusion
2GeV injection powering is very challenging and a lot of technologies that have never been used before are involved.
Even if standardization is EPC goal (almost mandatory to meet the LS2 target), a lot of power converters studies/developments are ongoing as the requirements are very specific.
Several specifications/operational requirements are urgently needed.
Integration studies in the tunnel are ongoing (thanks to ABT !) and have to progress with more details (transformers, current measurement systems, diodes assembly, striplines, etc…).
6 July 2018