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Bipolar high voltage power supply for storage chamber in a neutron EDM (nEDM) experiment
HCB 40-200000 MOD
02.10.2018 FuG Elektronik GmbH 3
General requirements to a bipolar power supplyA bipolar high voltage power supply shall deliver an adjustable high voltage at the output with an adjustment range from negative maximum to positive maximum and with a zero-crossing without any delay and with no regulation anomalies during zero-crossing.To fulfill these requirements, the power supply often needs full 4Q capability. It must be capable to handle the back-flow of energy from the load and to consume this energy.
Special requirements for the nEDM experiment- 200 (250) kV maximum output voltage- 100 ppm stability and temperature coefficient- 5 ppm (1V)residual ripple (p.-p.)- Current up to 200µA with measurement range 20µA (1 nA resolution)- Ramping speed about 1kV/s
Possible attempts and solutions with advantages and disadvantages- mechanical or electromechanical solution- Linear regulation - SMPS with voltage divider- SMPS with intrinsic voltage divider
Solution and problems to be solved- electrical principle- mechanical solution- problems and limitations
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Bipolar:
At least first and third quadrant
has to be covered.
No time delay during zero-
crossing.
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200 (250) kV maximum output voltage
100 ppm stability and temperature coefficient
5 ppm (1V)residual ripple (p.-p.)
Current up to 200µA with measurement range 20µA (1 nAresolution)
Low stored energy, fast recovery after discharge
Adjustable current limitation
Ramping speed about 1kV/s (5kV/s)
Digital programming (RS232 with optical fiber)
Special interlock (also via interface)
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Mechanical or electromechanical solutionPublication Borisov, Yu. et al.,
Leningrad 1987: „200 kV
stabilized voltage source with
controlled polarity“
Polarity reversal switch
Hard to make for 200kV (oil insulation!)
No zero-passing without delay
Possible EMI due to motors and switches may
disturb measurement.
Noisy Motor-
Generator
Nevertheless – a
switch is necessary.
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Linear regulation
No semiconductors for such high voltage
Serial connection of semiconductors?
Electron Tubes?
SMPS with voltage divider
High cross current (low efficiency, problem of heat dissipation)
Internal double of output voltage must be produced
Additional feature: full 4Q capability
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Application example for 10kV
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Application example for 200kV
SMPS with intrinsic voltage divider
Lower cross current
Internal voltage can be reduced
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Problems and limitations
Careful design of HV part is essential for function of power supply. Theoretical calculations and computer simulations are very helpful, but sometimes it needs corrections by practical experience.
Heat dissipation depends on voltage and nominal output power. Limits are given by thermal features of isolation material. Oil is an option but has other disadvantages.