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Wed-Af-Po3.23-07

Modular Toroidal Copper Coil for the Investigation of Inductive Pulsed Power Generators in the MJ-Range2) France Laboratoire National des Champs Magnétiques Intenses (LNCMI), Toulouse, FR1) French-German Research Institute of Saint-Louis (ISL), Saint-Louis, FR O. LIEBFRIED1), V. BROMMER1), H. SCHARF1), M. SCHACHERER1), P. FRINGS2)

Toroidal designavoids magnetic stray fields

Shavranov or Princeton D-shapeto minimize bending forces and maximize L/R

Design and construction of the short time 1 MJ magnetic energy storage

[1] S. Hundertmark, G. Vincent, F. Schubert, J. Urban The NGL-60 Railgun, in IEEE Transactions on Plasma Science, vol. 47, no. 7, pp. 3327-3330, July 2019

[2] O. Liebfried, V. Brommer, S. Scharnholz Development of XRAM generators as inductive power sources for very high current pulses, 19th IEEE Pulsed Power Conference (PPC), San Francisco, CA, 2013, pp. 1-6, 2013

[3] P. Dedie, V. Brommer, S. Scharnholz ICCOS Countercurrent-Thyristor High-Power Opening Switch for Currents Up to 28 kA, in IEEE Transactions on Magnetics, vol. 45, no. 1, pp. 536-539, Jan. 2009

[4] O. Liebfried Review of Inductive Pulsed Power Generators for Railguns, in IEEE Transactions on Plasma Science, vol. 45, no. 7, pp. 1108-1114, July 2017

[5] E. Spahn, M. Lichtenberger, F. Hatterer Pulse forming network for the 10 MJ-railgun PEGASUS, in Proceedings 5th European Symposium of Electromagnetic Launch Technologie, Toulouse, FR, Apr.10-13 1995

Coil specifications

NO. OF SEGMENTS 20OUTER DIAMETER 960 mmWITH CONNECTORS 1030 mmINNER DIAMETER 260 mmHEIGHT 423 mmVOLUME 220 lWEIGHT 1050 kgMAX. VOLTAGE 5 kVDC RESISTANCE 5 mWINDUCTANCE @ 50 Hz 1 mHENERGY DENSITY @ 50 kA 5.7 MJ/m3

SPECIFIC ENERGY @ 50 kA 1.2 kJ/kg

RCL-meter measurement

Frequency Rise time Coil resistance t300 K 400 K

0 Hz 5 mW 3.3 s

1 Hz 250 ms 8.5 mW 3.8 s

10 Hz 25 ms 16 mW 2 s

50 Hz 5 ms 30 mW 1 s

1 kHz 250 mm 117 mW 0.3 s

Approximation of coil restistance and heating time t300 K 400 K in relation to pulse risetime (linear charging current with a maximum of 45 kA assumed).

Indu

ctan

ce (m

H)

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

0Frequency (Hz)

25 100 225 400 625 900

COMSOLToroidSingle sub-coil x 20

x 2.5 due to coupling

5 mΩ + 3.88 √ fCOMSOL

ToroidSingle sub-coil x 20

Sqrt of Frequency ( )√Hz0 5 10 15 20 25 30

0

50

100

150

Res

ista

nce

(mΩ

)

© IS

L 20

19 -

R-0

3/19

/01/

000/

0/00

-00/

PO

-191

/201

9 -

CO

M-E

D (

AK

) -

08/2

019

PresenterDr. Oliver LIEBFRIED

Tel.: +33 (0)389 69 51 96Email: oliver.liebfried@isl.eu

We acknowledge the assistance of all of those who helped with the preparation of the coil and this poster. Special thanks goes to Bernhard Grasser and Veronika Aker in this respect.This work was supported by the French Government Defense procurement and technology agency (DGA) as part of the ANR Astrid program under Grant ANR-14-ASTR-0025.

Acknowledgement

References

  The coil will be used to build a 1 MJ XRAM generator which should demonstrate the feasibility of this technology in combination with a medium caliber railgun of the ISL. Other inductive pulse power generator topologies might be investigated as well.

  A different coil design with wire windings and an energy density of 40 MJ/m3 is currently in development.

Outlook

  A toroidal storage coil was realized by milled and slit D-shape copper discs with screw connections and GRP discs for insulation.  The coil design provides large strength with respect to Lorentz forces perpendicular to the coil surface but suffers from a pronounced skin effect.  Resistance increases with frequency according to R( f ) = 5 mW + 3.88 mW x f

  Coil was tested with pulsed current up to 50 kA (1.25 MJ)  Coil meets the requirement for the envisaged inductive pulsed power generator experiments.  Modular design allows for variation of windings and thus different generator setups (i.e. XRAM, pulse transformer, etc.).

Conclusion

180 GRP discsinsulate the windings from

each other. Their thickness is 2 or 1.5 mm

Coil interfacesallow for electric connections to each sub-coil and force locking between the last windings

Wooden blockssupporting the coil.

Kept in place by a tension belt

Scale 1:2.35

Nine Cu discsform the windings of onesub-coil. Screw interconnections allow for the variation of wind-ings per sub-coil

Twenty sub-coilscan be interconnected or connected individually

GRP disc with Bdots and PT1000sfor measuring temperature

and B-field at different locations

Application

ISL Railgun NGL-60

LENGTH 6 mCALIBER 60 mmPROJECTILE MASS up to 2 kgACCELERATION TIME 5 ms @ 2500 m/sMAX. RAILGUN CURRENT 2.5 MABREECH VOLTAGE < 3000 VPOWER SUPPLY 10 MJ / 10 kV

capacitor bank

Battery

Battery

Switch

DCDC

Charger Capacitor Switch

Switch

Switch LoadInductor

Switch LoadInductor

Battery – capacitive pulse power supply

Battery – inductive pulse power supply

Ragone plot*

Ene

rgy

Den

sity

[Wh/

kg]

0.01

0.1

1

10

100

1,000

Powerdensity [W/kg]10 100 1,000 10,000 100,000 1e+06

10 h 1 h6 min 36 s

3.6 s360 ms

36 ms

3.6 ms

360 µs

36 µs

Supercaps

Lead-acid

LiCoO2

NiMH LiFePO4

CoilsHPG

Pulsed Alternators

Dielectric CapacitorsSMES

Flywheels

SMES - Superconducting Magnetic Energy StorageHPG - Homopolar Generator

* based on available components (2015)

An inductive pulsed power supply system promises to be smaller than a capacitive system due to fewer conversion steps and a higher energy density of inductive storage.

XRAM generator as inductive pulsed power supply for a railgun

Operation principle [2]

L 1

T2

L 2

Ub

T1

Ccc1

+ −

D11

D22

Tcc

RL

L LD12

D21

Ccc2

+ −Dcc2

Dcc1

Stag

e1

Stag

e2

Step 1: Ub charges L1 and L2 via T1 and T2 in series connection

Step 2: Tcc initiates discharge of pre-charged Cccs via Dccs and the load

Step 3: T1 and T2 switch-OFF due to neg. voltageStep 4: L1 and L2 are discharged in parallel

connection to the loadSchematic of a 2-stage XRAM generator with ICCOS opening switches [3]

Principal waveforms of charging and load current

Goal: A demonstrator of a 1 MJ XRAM generator Required: A modular inductive storage with 20 stages, R < 10 mW and 1 MJ (i.e. L = 1 mH, I = 45 kA)

FEM simulation

FEM SOFTWARE COMSOL Multiphysics®

USED PACKAGES AC/DC: Magnetic Fields Structural Mechanics : Solid Mechanics

STUDY TYPE Frequency Domain (f = 62.5 Hz)

MESH 373642 tetrahedral elements

BOUNDARY CONDITIONS x-y cut plane airspace: Magnetic Insulation x-y cut plane conductors: in/output current 50 kAr-z cut planes: Perfect Magnetic Conductor Roller boundaries: windings fixed at x-y-cutplane and in toroidal direction Body load: Lorentz force

Inductance @ 62.5 Hz: 1 mHResistance @ 62.5 Hz: 33 mW

Von Mises stress of 115 MPa @ I = 50 kA E = 1.25 MJ Oxygen free copper with a proof strength 0.2% of ≥ 180 MPa was used

Considered coil designs [4]

Jelly-roll coil construction

Toroidal coil Bitter coil construction

Force-balanced coil D-shape (bending free)

Solenoidal coil

Design chosen: toroidal design for EMC reasons + Bitter coil design for manufacturing reasons + D-shape for improving L/R

Pulsed power testing

S

C D

LPFU

LCoil

RCoil

RCircuit

Cur

rent

(kA)

0

20

40

60

Volta

ge(k

V)

0

1

2

3

4

5

Time (ms)0 10 20 30 40

Coil connected to the 10 MJ PEGASUS capacitor bank [5]

Setup Voltage and current measurement

Magnetic field measurement Temperature measurementComparison with simulation

Sensors Simulation Measured Error

Bdot B Bj

Breal100realB B

Bϕ

ϕ

−×

2 4.98 T 4.92 T 4.8 T 2.4 %

4 6.66 T 6.58 T 6.4 T 2.7 %

7 8.04 T 7.95 T 7.5 T 5.7 %

8 8.04 T 7.95 T 7.6 T 4.4 %

10 7.62 T 7.53 T 6.8 T 9.7 %

12 6.64 T 6.55 T 6.3 T 3.8 %

Tem

pera

ture

(°C

)

24

25

26

27

28

Time (s)0 20 40 60 80

∆T= 2.5C C∆T= 1.7

( )( ) ( )1.43

p

dI tI t U t L dtdtT C

c w

∫ − ∆ = = °

2( ) I ( ) 1.67p

R f t dtT Cc w∫

∆ = = °

HS camera recording

Tiny gaps due to production tolerances allow movement of coil windings towards the center (contracting forces).No change of coil structure could be observed.

Battery

Battery

Switch

DCDC

Charger Capacitor Switch

Switch

Switch LoadInductor

Switch LoadInductor

Battery – capacitive pulse power supply

Battery – inductive pulse power supply

180 Cu discsmilled from copper plates

with a wedge-shape to be arranged in a torus

without gap

Measured and simulated inductance as function of frequency Measured and simulated resistance as function of frequency. Note that R is proportional to because of the skin effect f