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ISIS Electrical EngineeringGroup Structure
Group Leader
ESSOPulsed Power
PSU Development
DC Power
Controls &Electronics
3Staff
4Staff
5Staff
3Staff
9Staff
ISIS Electrical EngineeringGroup Structure
Mike GloverGroup Leader
ESSO Pulsed Power PSU DevelopmentDC PowerControls &Electronics
VacancySection Leader
Geoff MartinEngineer
Adrian McFarlandSection Leader
Stephen RuddleEngineer
Jim GraySection Leader
Tim CarterEngineer
Husam Al-HakimEngineer
Matt NorthEngineer
Chris GascoyneTechnician
Steve StonehamSection Leader
VacancyEngineer
John BowsleyContractor
Steve WestEngineer
Andy KimberEngineer
Martin HughesGraduate Engineer
Neil FarthingContractor
Steve WarnerOffice Manager
VacancyIT Manager
Neil KellyCAD
Martin DobbsCAD
Vacancy CAD
Vacancy CAD
Austine BrineContractor
Paul WadeContractor
Areas of Responsibility
• ISIS Synchrotron Power Supplies
• ISIS Extracted Proton Beam Line Power Supplies
• ISIS Neutron Beam Line Chopper Power Supplies
• Electrical Engineering of ISIS Control Systems for:
• Vacuum Systems
• Water Plant Systems
• Electrical Engineering of Neutron Instrument Beam Line Installations
ISIS Synchrotron Power Supplies
• Main Magnet “White Circuit”– 14.4kV 650ADC 400AAC
• Injection & Extraction Septum– 5kA & 10kA 50V DC
• Injection Dipole– 50Hz 13kA 500µS Flat Top 100µS Rise Time
• Ring Steering & Trim Quadrupoles– 4 Quadrant 150kA/S 250 Amp Programmable
• Fast Extraction Kicker Magnets– 50Hz 40kV 5kA 500nS Flat Top 80nS Rise Time
Injection Septum
•Deflects the injected beam into the aperture of the injection dipole magnet and onto the foil
•200kW
•5000 Amps
•40V
•1416 Transistor Regulator
•100ppm stability
Extraction Septum
Magnet Bend 21º
10,000 Amps 50V
11kV Supply Rectifier Transistor Regulator
4 Sets of 24 Transistor Banks
2304 Transistors
Extraction of Beam
• At Extraction
– Protons Circulating at 800 MeV
– Two bunches with 200 ns gap
• Extraction System
– 3 fast kicker magnets
deflect the beam into …
– a septum magnet
which lifts it into the EPB
• Kickers need to be fast to avoid beam loss
– Go from zero to full field between passage of bunches
Extraction Details
• Kickers
– 3 units give 15 mr kick
– Rise Time 80 nS
– Flat Top 500 nS
– 5000A
– 40kV
– 50Hz pulsed
• Septum
– ~ 8 m downstream
– 8 Turn, 8900 A
– DC
– 1.8 m long (21 degrees)
– Lifts beam out of machine
ESSONeutron Beam Line Installations
•Complete electrical design
•Electrical Supply
•Detector Cabling
•Chopper Cabling
•Vacuum System Controls
•Several kilometres of cabling per beam line
• Main magnet systems• MM Power Supply and the White Circuit
• Capacitor bank replacement• UPS• Replacement 1MJ Storage Choke
• Summary
Outline
Magnet systems
• Main Magnets
10 Bending Dipoles10 Singlet Quadrupoles10 Focussing Doublet
Quadrupoles.
• Corresponds to 10 superperiods
Main magnet power supply
For successful acceleration the same magnetic field is required in all the main magnets
Main Magnets per super period:1 Dipole1 Singlet Quadrupole1 Doublet Quadrupole
How do we connect these?One power supply per super periodMain Magnet System operates at 14.4kVCurrent changes from 250A to 1050 Amps
Peak Power = 15.1 MVAFor 10 super periods the Peak Power
Required = 151 MVA
Excessive Power Required !
Main magnet power supply
Magnets have InductanceInductance can store energy E = ½ LI2 Capacitors also store energy E = ½ CV2
Resonate the stored energy between Inductor and capacitor:
With no losses in the system the impedances of the Inductance and the Capacitance would be identical and energy would be transferred with an alternating current between them and at a resonant frequency.
Inductance reactance XL = Capacitive reactance XCωL = 1/ωC ω = 2π f Resonant Frequency f = 1/(2π√LC )
Main magnet power supply
• Normal Temperature Magnets have Resistance
• Capacitors have losses
• Cables have losses
• If the losses << Inductance we have a high ‘Q’ oscillating system.
• We just require to supply make up power for the resistive and AC losses in the Magnets, Cables and Connectors.
The White Circuit
WHITE CIRCUIT M G White, Princeton (1956) CERN Symposium
• Oscillate the magnet cell using capacitors and choke.
• Connect all the magnets together electrically and same current flows through each magnet.
• Permit DC bias current through split choke secondary winding
• Power required is to make up for the resistive losses in the copper, ac losses in the magnets and power supply losses.
IM = IDC – IAC cos ω t
Total of 1.75MW (150MVA peak for non resonant circuit)
Main magnet power supply
• Replace capacitor bank with smaller more efficient units. • Replace the Motor Alternator Set with a UPS System• Replace the Choke.
– Split the Choke into 10 separate units and build spare as well.
PROGRESS TO DATECapacitor bank replaced (2002)
UPS system currently on order.
Build a scale model to prove theory of split choke.Scale model chokes currently being ordered.
Previous Motor Alternator Set
• Electromechanical• Single phase output• 2 phases connected line to line and 1 disconnected• Alternator phase locked to ISIS 50Hz reference• 100Hz induced harmonic between raw mains and reference signal
DCMotor Alternator
BrentfordExcitation
PSU 12KVA
Mains supply
Phase locked toISIS 50Hz reference
signal
transformer
5KVsingle phase
3.6KVsingle phase
Storagechokeand mainmagnets
shaft
Current Motor Alternator Set
DCMotor Alternator
BrentfordExcitation
PSU 12KVA
Mains supply
Phase locked toISIS 50Hz reference
signal
transformer
5KVsingle phase
3.6KVsingle phase
Storagechokeand mainmagnets
shaft
UPS
Phase locked toISIS 50Hz reference
signal
• Alternator and UPS phase locked to ISIS 50Hz reference • Factor of 2 improvement in AC stability
New UPS system
• Motor alternator set replaced with 4 300KVA units (1 redundancy)• UPS units currently on order• Installed by Q4 2004
transformer
3.6KVsingle phase
Storagechokeand mainmagnets
240Vthree phase
Gray convertercircuit
720Vsinglephase
Current 1MJ, 2H Storage Choke
Ex-NINA, manufactured in the 1960’s
Ten interleaved primary and secondary windings
Choke windings and core: 90 tonnesTotal weight (inc. oil): 120 tonnes
30 years of service
State of insulation unknown, leaks oil, failure would result in ISIS being down for extended period of time
Storage Choke
Replacement chokes
…X10
Current 2H storage choke
10 off replacement 200mH chokes
1/5 scale models 40mHMinimise financial and technological riskDue September 04
Full scale prototype/spare
Replacement chokes
Flux DensityB (T)
2.150
1.935
1.720
1.505
1.290
1.075
0.860
0.645
0.430
0.215
0.000
Flux DensityB (T)
1.570
1.413
1.256
1.099
0.942
0.785
0.628
0.471
0.314
0.157
0.000
• Most probable design is a ‘frame’ type storage choke
Energy stored (air gaps) = ½ L I2
Energy stored/unit volume = ½ μ0 B2
• Calculate dimension of air gapsFor 200mH, 1010A, 100KJ, 0.9T: Volume ~0.3m3
• Size and distribution of these critical in controlling losses
Replacement chokes
Testing of scale models to take place September 2004
• Losses• Stray magnetic fields• Leakage inductance• Linearity• Noise (mechanical)• Cost