Magnet Power Supply System

T. OkiT. Adachi
T. Kawamoto
T. Sueno
N. Tokuda
18th KEKB Accelerator Review Committee

Contents-

New power supplies to be manufactured for SuperKEKB.

-

Test results of the megawatt-class power supply
setting resolution
current stability-

Power supplies for the superconducting Magnets

New Power supplies to be manufactured for SuperKEKB (1/2)
Power# of power supplies

Loads< 70 kW

23*

Damping Ring (Q, B …)

< 630 kW2†

Damping Ring (Bends.)< 30 kW30‡

Damping Ring (Q, SX)< 50 kW91‡

Local Q

< 0.8 kW(± 10 A)

29†+~70‡

Steerings, Corrections, …

0.35 kW (± 70 A)

4‡+36♦

QCS corrections*:in FY2011;†: in FY2012; ‡: in FY2013; ♦ : in FY2014 or later.

Target spec. (except for steerings)
Setting resolution

20-bitStability< 20 ppm / dayRipple< 10 ppm

Comparable with the spec. for KEKB power supplies.

New Power supplies to be manufactured for SuperKEKB (2/2)
Power# of power supplies

Loads

0.95 MW

2*LER / HER Bends.

0.4~1 MW

8* / 1†

LER / HER Wiggs.

< 20 kW (< 2 kA)

5‡+7♦

QCS main, Solenoid*:in FY2011;†: in FY2012; ‡: in FY2013; ♦ : in FY2014 or later.

Higher performances are required.
Target spec.
Setting resolution

24-bitStability< 2 ppm / dayRipple< 1 ppm24-bit current-setting resolution
New commercial use 20-bit DAC was released in 2010 by Analog Devices.
Summing the output of sixteen ( = 24) 20-bit DAC’s.
20-bit24-bit20-bit
DAC #16

1/24

1/24

Codetranslation
byFPGA+
1/24

20-bit20-bit
DAC #220-bit20-bit
DAC #1

1/24

1/220×1/24

24-bit control board

Analog DevicesAD5791BRUZ

Eight DACs are placed each side of the board

Digital feed back control for high current stability
24-bit board
DAC+

Setting value
in 24-bit+-DAC

Error Detection
DMMDCCTNP
Output terminal+current loop-

B2P Power supply (LER Bend) under testing at factory

860 A, 1100 V (946 kW)

Test result: setting resolution (BWDNLP)Power supply was operated in the rated current of 1400 A with a dummy load.
Output current was measured by a DCCT and DMM(10 V range, 2 PLC, 10 moving Fit)
Decreasing DAC input digital value by 16 least significant bit (LSB).

Monotonic response was obtained for 16 LSB step.
Higher resolution can be expected.

Test result: current stability (B2P)
Power supply was operated in the rated current of 860 A with a dummy load.
Output current was measured by a DCCT and DMM(10 V range, 2 PLC, 10 moving Fit)

High current stability was achieved:
1.2 ppm/4 hrs. as a mean value with low σ (0.67 ppm)

Test result: current stability (7.5 kW medium-class PS)
Performed by using a medium-class power supply (15 V, 500 A).
measured by DMM (20 V range, 50 PLC, 10 moving Fit)

More higher stability: 1 ppm (peak to peak)/hr. with low σ (0.16 ppm)

Power supplies for the superconducting Magnets-to be fabricated in FY2013 for the left-side of I. P.
(1) 4 power supplies for 4 quadrupole magnets each2000 A, 8 V (QC1LE)
1250 A, 5 V (QC2LE)
1800 A, 8 V (QC1LP)
1000 A, 5 V (QC2LP)(2) 1 power supply for a solenoid
400 A, 15 V (ESL)
Resolution

24-bitStability< 2 ppm / 8 hrs.

Ripple< 1 ppm(3) 4 or more bipolar power supplies for correction coils± 70 A, ± 5 V
Resolution
20-bitStability< 20 ppm / 8 hrs.

Ripple< 5 ppm

Detailed parameters for the power supplies of (1) and (2)Quadrupoles

Solenoid

QC1LE QC2LE QC1LP QC2LP

ESLOperating current (A)

1577

977

1625

877

348

Stored energy (kJ)

4.38

10.38

1.43

3.66

171

Inductance (mH)

2.19

13.28

0.88

7.32

2138

Resistance of cable (mΩ)

12

1

2

5

Withstanding voltage (V)

200

200

200

200400

Rated output current (A)

2000

1250

1800

1000

400

Rated output voltage (V)858512

Protection Resistor (Ω)

0.10

0.16

0.11

0.20

1.0

Allowed time delay forprotection circuit (ms)< 20< 20< 20< 20< 100

Low inductance may lead to ripples/noises.

Damping ratio of alternating magnetic field
Eddy current damps the magnetic field inside of beam pipe.

Bin=Bout1bt 1+  µ0π f ρ 

2b: outer diametert: thickness
ρ: conductivity
Beam pipe at IP is made of lower conductivity material,so that the damping effect cannot be expected: low ripple PS is essential.
An additional reactance will be required as a component of passive filter.
Active filter or improved minor feedback loop may also be required.

Summary-

Small/medium/Large-class power supplies have been manufactured.

-

For the high-spec. power supplies, 24-bit setting resolution and digital
feedback system have been developed and applied. The test results
are satisfactory.

-The most challenging task will be required for QCS power supplies:
the ripple/noise will be a key issue.

-Overhaul has been in progress for reused power supplies.

Back-up slideNon linearity and monotonicity

LSB: least significant bit
DNL: differential non linearity
INL: integral non linearity

Lose monotonicity

AD7846K (16-bit): DNL ±0.5 LSB max
INL ±2 LSB
AD5791B (20-bit): DNL ±0.75 LSB typ. (test result: <±0.1 LSB）
INL ±0.5 LSB typ. (test result: -0.2～+0.6 LSB）

Why sixteen DAC's 24-bit system?
Care must be taken to the monotonicity of two DAC’s 24-bit system

Not so badBad

24-bit current-setting resolution
Two 20-bit DAC’s are combined.

Setting value
in 20-bit (major)
Setting valuein 4-bit (minor)

1/220++

DAC+1/24

1/24DAC

Analog Devices AD5791BRUZ

Digital feed back control for high current stability+

Setting value
in 20-bit (major)

DAC
-

1/24+

Setting valuein 4-bit (minor)

+

-DAC

Error Detection
DMM
DCCT
N
P
Output terminal+

current loop-

minorvoltage loop+-

How much jitter on the measured current
For precious control, lower jitter is necessary on the current monitoring.
Current is measured by a DCCT and a DMM.

Fluctuation (σ) of DCCT
output during 5min (µV)

Power supply: Transistor-dropper type (1000 A-30 V).
DCCT: 1000 A / 10 V output
DMM: KEITHLEY 2002 (10 PLC, 20 V range)
1010 µV corresponds to 1 ppm

8642

Noise level: 0.6 µV

00200

400 600 800
Current (A)1000

Detailed parameters for the power supplies of (1) and (2)Load parameters

Quadrupoles

Solenoid

QC1LE

QC2LE

QC1LP

QC2LP

ESL

Operating current (A)

1577

977

1625

877

348

Stored energy (kJ)

4.38

10.38

1.43

3.66

171

Inductance (mH)

2.19

13.28

0.88

7.32

2138

Resistance of cable (mΩ)

12125Withstanding voltage (V)200200200200400

Power supplies and quench protection circuits(resistor and SCR switch or circuit breaker)
Rated output current (A)

2000

1250

1800

1000

400

Rated output voltage (V)

858

512

Protection Resistor (Ω)

0.10

0.16

0.11

0.20

1.0

Allowed time delay forprotection circuit (ms)< 20< 20< 20< 20< 100

Remote control operation, which provides by an ARCNET interface, is required.

Specifications in the current of the power supplies of (1) and (2)QC1LE, QC2LE,
QC1LP, QC2LPESLShort term stability< 2 ppm/8 hrs

Long term stability< 10 ppm/monthRipple (< 10 kHz)< 1 ppm (rms, total harmonic distortion)

Noise (> 10 kHz)< 10 ppm (zero-peak) (goal)

Setting resolution

24 bitRamp rate

10 A/s4 A/sDetailed parameters for the power supplies of (3)Load parameters

Correction coils

Operating current (A)-70 ~ +70

Stored energy (J)0.54 ~ 21

Inductance of magnets L (mH)

0.22 ~ 8.7

Resistance of cable (mΩ)

25Withstanding voltage (V)200Power supply and quench protection circuit (Diode)
Rated output current (A)± 70

Rated output voltage (V)±5Current decay timewith any time delay (ms)< 100

Remote control operation, which provides by an ARCNET interface, is required.

Specifications in the current of the power supplies of (3)Short term stability< 20 ppm/8 hrs

Long term stability< 100 ppm/monthRipple (< 10 kHz)< 5 ppm (rms, total harmonic distortion)

Noise (> 10 kHz)< 50 ppm (zero-peak) (goal)

Setting resolution

20 bitRamp rate

10 A/sExisting KEKB Power supplies
We have ~ 2300 power supplies:Class# of power supplies

Typical load

Small-class1885
Steering magnet etc(< 10 A, 0.5 kW)
To be reused
after appropriate maintenance and overhaul : in progress.
Medium-class
368
Local Quads(< 500 A, 100 kW)
To be reused.
Large-class
14
Quad families(< 500Current
A, 500 settingkW) resolution will be improved by 20-bit DAC.
Megawatt-class
Rubbished and replaced by 6newly developed
PSs: inprogress.
BendingandWigglers(< 1250 A, 1 MW)
Typical spec.
Stability< 20 ppm / dayRipple< 10 ppm

Setting resolution< ± 50 ppm (16-bit DAC)