magnetic core and semiconductor switch characterisation

Magnetic core and semiconductor

switch characterisation for an

Inductive Adder kicker generator

D. Woog

M.J. Barnes, J. Holma, T. Kramer

131/05/2017David Woog - FCC Week 2017, Berlin

• FCC-hh injection

• Inductive Adder concept

• Magnetic core characterisation

• Semiconductor switch characterisation

• Preliminary prototype design

• Milestones and next steps

Content

31/05/2017David Woog - FCC Week 2017, Berlin2

LHC

SPSFCC

Septum magnetsKicker magnets

FCC-hh injection system

Circulating bunch trains

Injected bunch train

Kicker (pulse)

generators

• Injection from high energy booster

(HEB) into FCC

• Injected bunch train needs to be

deflected onto the circular orbit

• Circulating bunches must not be kicked

• Pulsed magnetic field in kicker magnet

requires high power pulse generator


• Different high energy booster (HEB) options for FCC are in discussion, based on:

• SPS (0.45 TeV, 1.3 TeV)

• LHC (1.6 TeV, 3.3 TeV, 6.5 TeV)

• FCC (3.3 TeV, 6.5 TeV)

• In every case a reliable and fast injection kicker system is needed

• Baseline HEB is LHC at 3.3 TeVParameter Unit Value

Kinetic Energy [TeV] 3.30

Angle [mrad] 0.18

Pulse flat top length [µs] 2.00

Flat top tolerance [%] ±0.50

Field rise time [µs] 0.425

Voltage [kV] 15.70

Current [kA] 2.50

System impedance [Ω] 6.25

FCC-hh injection

Parameters for FCC-hh injection


FCC injection – generator options

• New pulse generator design is needed

• Thyratrons must be avoided as switch

• Semiconductor (SC) switches are a promising alternative

• Two main pulse generator designs based on SC-switches

under consideration:

Inductive Adder (IA)

Solid state Marx generator

Required field rise time: 0.425 µs

→ 0.350 µs of kicker magnet fill time

→ 0.075 µs remain for pulse current rise time

For machine protection reasons high reliability of the kicker system is

necessary!!

→ Thyratron pre-firing problems are unacceptable for FCC

High voltage thyratron

see Poster on Tuesday

by A. Chmielinska «Solid-State

Marx generator for use in the

injection kickers of the FCC»

~340m

m


• Stack of 1:1 transformers

• Secondary windings are connected in series

• Parallel branches of primary windings define max. output current

• Parameters such as insulation properties, parasitic inductances, etc. define system impedance

Inductive Adder concept

Schematic drawing of an IA [4]

𝐴c 𝐼sec

Stalk (secondary)

magnetic core𝐼prim

primary windinginsulation

parallel branches

PCB


Main components of the IA:

• Magnetic core (following slides)

• Semiconductor switches (following slides)

Pro Con

Based on semiconductor switches

• Ability to turn on and off current

• Hence eliminate PFN/PFL

Output transformer necessary

Modular design High energy storage in capacitors

All electronics ground referenced

Reduced maintenance

Larger dynamic range

Modulation of output pulse possible [5]

Simple replacement of components

Easy to adapt to different applications

Inductive Adder conceptAdvantages and disadvantages of the IA compared to traditional pulse generators (PFN, PFL)

• Pulse capacitor (tested and selected)

• Insulation material (selected)

• High voltage diodes


𝐴c =𝑡pulse ∙ 𝑉layer ∙ 𝛼m

∆𝐵c ∙ ηFe

• Important key component of the IA

• Dimensions and material characteristics are

important

• Saturation of core must be avoided

Large core cross sectional area 𝐴c needed

𝐿m𝑅c 𝑉out

Equivalent circuit of the core:

Pulse parameters 𝑡pulse, 𝑉layer

Magnetic flux density swing ∆𝐵c

Core fill factor ηFe

Security margin 𝛼m

Parameters of interest:

• Equivalent loss resistance (𝑅c)• Magnetizing inductance (𝐿m)

• B-H curve

• Frequency behaviour

• Biasing current (𝐼bias)

Magnetic core


Measured B-H cures of different core types

Nanocrystalline tape wound

core with 30 cm ruler


Thank you to Silvia Aguilera, Michal Krupa and Patrick Odier from CERN BE-BI group for

assistance with measuring the B-H curves.

Measurements on sample cores

Equivalent circuit of test setup:

Test setup for sample cores, based on the prototype for

CLIC DR IA :

• A MOSFET is discharging a capacitor over the primary

winding of the core

• The primary current is measured with a current sensor

• The output voltage is measured on the secondary

winding without load

• On another test setup the B-H curves were measured

Current sensor

Pulse capacitor

MOSFET

Core housing

(primary winding)

𝐿m𝑅c 𝑉out𝐶c𝑆

A


𝐼0

𝑅c =𝑉c𝐼0

𝐿m = 𝑉c ∙∆𝑡pulse

∆𝐼m

𝑡pulse = 4.2us

Pulse characterisation of cores

∆𝐼m

Core 1 2 3 4 5 6 7 8

𝑅c in Ω 55 50 65 75 150 160 230 200

𝐿𝐦 in µH 282 367 191 160 56 42 30 30.6

B-H shape square square square square linear linear linear linear

𝑉c = 350 V


Results of core measurements

Core 1 2 3 4 5 6 7 8 9 10

𝑅c in Ω 55 50 65 75 150 160 230 200 70 70

𝐿𝐦 in µH 282 367 191 160 56 42 30 30.6 28.8 28.8

B-H shape square square square square linear linear linear linear linear linear

∆𝑩𝐬𝐚𝐭 in T 2.4 2.4 2.4 2.4 2.4 2.4 2.1 2.1 2.0 2.0

𝑰𝐛𝐢𝐚𝐬 in A 1 1 1 1 15 15 5 5 20 20

Cores 1-4 have been chosen as they best suit the requirements:

• Highest inductance of all sample cores

• Biggest ∆𝐵sat• Low biasing current required

High inductance and ∆𝑩𝐬𝐚𝐭 improve the IA design. The higher

losses can be accepted.


Semiconductor (SC) switches to replace

Thyratrons:

SiC MOSFETs seem promising

Advantages compared to Si components

• Fast switching times

• Lower values of 𝑹𝐨𝐧(< 0.05 Ω)• Up to 1700 V available

• Wide bandgap technology is a ‘rather’ new

• Devices are still in development

• Nevertheless there are already suitable devices

available

• Capability of devices has to be measured

(𝑡r,0.5−99.5, 𝐼D,pulse(2.5μs,1kV))

• Radiation hardness of SiC devices is of interest

SiC devices 1 2 3 4

𝑉DS 1200 V 1200 V 1700 V 1200 V

𝑡r,10−90 32 ns 9 ns 20 ns 44 ns

𝑡f,10−90 28 ns 22 ns 18 ns 28 ns

𝐼D,25°C 90 A 80 A 72 A 95 A

𝐼D,pulse 250 A 190 A 160 A 237 A

𝑅on 25 mΩ 40 mΩ 45 mΩ 22 mΩ

Considerations on Semiconductor Switches

Examples for SiC MOSFETs available on the market:

• High 𝑉DS is required to reduce

number of layers

• High 𝐼D,pulse is required to reduce

number of branches

• High 𝑅on causes increased voltage

drop

• Fast rise time is required


The capability of different sample devices has been tested

• High current capabilities for ~2.5 µs pulse at 1 kV

• Fast current rise times at high voltage from 0.5 to 99.5 %

The switching behaviour of the devices is strongly dependend upon the gate driver circuit

Device 1 2 3

𝑡r,0.5−99.5 64 ns 100 ns 76 ns

𝐼pulse,2.5μs >200 A >200 A >200 A

Semiconductor switches characterisation

• Test results seem promising

• PSpice simulations with measured values show a sufficiently fast rise time

• Further measurements are ongoing

• Radiation hardness is of interest – tests have not been successful yet

• Any experience welcome!


Parameter Unit Value

Nr. of constant voltage layers - 21

Nr. of modulation layers - 2

Nr. of branches per layer - 24

Characteristic impedance Ω 6.25

Voltage per layer V 960

Current per branch A 105

Total height mm ~1200

Output voltage kV 15.62

Output current kA 2.5

Based on the component characterisation a prototype IA has been

designed:

• 21 constant voltage layers

• 2 special (modulation) layers for ripple and droop compensation

• 24 parallel branches per layer

Preliminary prototype IA design


• Production of hardware components (designed)• Core housing

• Stalk

• End caps

• Development of final PCB (design ongoing)• Gate driver circuit

• MOSFET switch

• HV diode

• Obtain outstanding parts and start prototype assembling

Milestones and next steps

20192018201720162015

• Optimisation

• Final prototype (21+2 layers)

• Final measurements

• Contribution to FCC CDR

• Basic design steps

• Definition of component

requirements

• Component selection

• Characterisation of

components

• Start of hardware design

• Hardware design

• First prototype (~5 layers)

• Measurements

Next steps:


Thank you

for your attention!References:

[1] L.S. Stoel et al., “High Energy Booster Options for a Future Circular Collider at CERN”, proceedings,

IPAC’16, Busan, Korea (2016).

[2] D. Woog et al., «Design of an Inductive Adder for the FCC Injection Kicker Pulse Generator», to be

published in the IPAC’17 proceedings, Kopenhagen, Denmark (2017).

[3] M. J. Barnes et al., “Pulsed Power at CERN”, to be published in the EAPPC 2016 proceedings, Lisbon,

Portugal (2016).

[4] T. Kramer et al., “Considerations for the injection and extraction kicker systems of a 100 TeV centre of

mass FCC-hh collider”, IPAC’16, Busan, Korea (2016).

[5] J. Holma et al., “Measurements on prototype inductive adders with ultra-flat-top output pulses for CLIC

DR kickers”, proceedings, IPAC’14, Dresden, Germany (2014).


Backup


Function

generator

OscilloscopePower supply

Amplifier, incl. 1 Ω Shunt to measure 𝐼prim~ 𝐻

Test core

RC integrator

to measure

𝑈sec 𝑑𝑡 ~ 𝐵

Current

limiting

resistor

Other required parameters:

Core dimensions, weight, fill factor,

no of windings Thanks to S. Aguilera and M. Krupa

BH curve measurement test setup from BE-BI-PI


• Radiation hardness of power semiconductor devices is a real concern

• High energy hadrons (HEH, >20 MeV) can cause single event

burnouts (SEB) in power MOSFETs

• SEBs cause short circuits between drain and source

• The behaviour of Si semiconductors under radiation is known

• Little experiences with SiC semiconductors as a new device technology

• Radiation hardness tests in the CHARM facility at CERN have been

successfully made with Si MOSFETs, GTOs and IGBTs

• Using the existing test setup to test SiC MOSFETs was more difficult than

expected

• Reliable measurements were not possible with this setup until now

• Over current protection needs to be adapted to SiC specification

• Any existing experiences in this field are interesting

Radiation hardness tests on SiC MOSFETs


magnetic core and semiconductor switch characterisation

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