4 Areas of Responsibility ISIS Synchrotron Power SuppliesISIS Extracted Proton Beam Line Power SuppliesISIS Neutron Beam Line Chopper Power SuppliesElectrical Engineering of ISIS Control Systems for:Vacuum SystemsWater Plant SystemsElectrical Engineering of Neutron Instrument Beam Line Installations
5 ISIS Synchrotron Power Supplies Main Magnet “White Circuit”14.4kV 650ADC 400AACInjection & Extraction Septum5kA & 10kA 50V DCInjection Dipole50Hz 13kA 500µS Flat Top 100µS Rise TimeRing Steering & Trim Quadrupoles4 Quadrant 150kA/S 250 Amp ProgrammableFast Extraction Kicker Magnets50Hz 40kV 5kA 500nS Flat Top 80nS Rise Time
6 Injection SeptumDeflects the injected beam into the aperture of the injection dipole magnet and onto the foil200kW5000 Amps40V1416 Transistor Regulator100ppm stability
7 Extraction Septum Magnet Bend 21º 10,000 Amps 50V 11kV Supply Rectifier Transistor Regulator4 Sets of 24 Transistor Banks2304 Transistors
8 Extraction of Beam At Extraction Protons Circulating at 800 MeV Two bunches with 200 ns gapExtraction System3 fast kicker magnetsdeflect the beam into …a septum magnetwhich lifts it into the EPBKickers need to be fast to avoid beam lossGo from zero to full field between passage of bunches
9 Extraction Details Kickers 3 units give 15 mr kick Rise Time 80 nS Flat Top 500 nS5000A40kV50Hz pulsedSeptum~ 8 m downstream8 Turn, 8900 ADC1.8 m long (21 degrees)Lifts beam out of machine
16 Main magnet power supply For successful acceleration the same magnetic field is required in all the main magnetsMain Magnets per super period:1 Dipole1 Singlet Quadrupole1 Doublet QuadrupoleHow do we connect these?One power supply per super periodMain Magnet System operates at 14.4kVCurrent changes from 250A to 1050 AmpsPeak Power = 15.1 MVAFor 10 super periods the Peak PowerRequired = 151 MVAExcessive Power Required !
17 Main magnet power supply Magnets have InductanceInductance can store energy E = ½ LI2Capacitors also store energy E = ½ CV2Resonate 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 fResonant Frequency f = 1/(2π√LC )
18 Main magnet power supply Normal Temperature Magnets have ResistanceCapacitors have lossesCables have lossesIf 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.
19 The White CircuitWHITE CIRCUIT M G White, Princeton (1956) CERN SymposiumOscillate 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 windingPower 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 tTotal of 1.75MW (150MVA peak for non resonant circuit)
22 Main magnet power supply Replace capacitor bank with smaller more efficient units.Replace the Motor Alternator Set with a UPS SystemReplace 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.
26 Previous Motor Alternator Set BrentfordExcitationPSU 12KVAMains supply5KVsinglephase3.6KVsinglephaseStoragechokeand mainmagnetsDCMotorAlternatorshafttransformerPhase locked toISIS 50Hz referencesignalElectromechanicalSingle phase output2 phases connected line to line and 1 disconnectedAlternator phase locked to ISIS 50Hz reference100Hz induced harmonic between raw mains and reference signal
27 Current Motor Alternator Set BrentfordExcitationPSU 12KVAMains supplyPhase locked toISIS 50Hz referencesignalUPS5KVsinglephase3.6KVsinglephaseStoragechokeand mainmagnetsDCMotorAlternatorshafttransformerPhase locked toISIS 50Hz referencesignalAlternator and UPS phase locked to ISIS 50Hz referenceFactor of 2 improvement in AC stability
28 New UPS system Motor alternator set replaced with 4 300KVA units threephase720Vsinglephase3.6KVsinglephaseStoragechokeand mainmagnetstransformerGray convertercircuitMotor alternator set replaced with 4 300KVA units(1 redundancy)UPS units currently on orderInstalled by Q4 2004
30 Storage Choke Current 1MJ, 2H Storage Choke Ex-NINA, manufactured in the 1960’sTen interleaved primary and secondary windingsChoke windings and core: 90 tonnesTotal weight (inc. oil): 120 tonnes30 years of serviceState of insulation unknown, leaks oil, failure would result in ISIS being down for extended period of time
31 Replacement chokes Current 2H storage choke 10 off replacement 200mH chokes…X101/5 scale models 40mHMinimise financial andtechnological riskDue September 04Full scale prototype/spare
32 Replacement chokesMost probable design is a ‘frame’ type storage chokeEnergy stored (air gaps) = ½ L I2Energy stored/unit volume = ½ μ0 B2Calculate dimension of air gapsFor 200mH, 1010A, 100KJ, 0.9T: Volume ~0.3m3Size and distribution of these critical in controlling losses
33 Replacement chokesTesting of scale models to take place September 2004LossesStray magnetic fieldsLeakage inductanceLinearityNoise (mechanical)Cost
34 Summary New capacitor banks Installed 2002 New UPS system Installed by Q4 2004New split choke systemScale model testing Q4 2004Prototype and production chokes 2005/6