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Power Supply Regulation

Power Supply Regulation. WBS 1.1.3 Power Supply System Level 3 Manager Nancy Grossman FNAL June 28, 2001. Overview of Regulation Needs. 7 Magnet Strings with regulation requirements ranging from 55 ppm to 400 ppm. 55 ppm means +/- 55 ppm relative to the flattop operating current (RMS).

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Power Supply Regulation

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  1. Power Supply Regulation WBS 1.1.3 Power Supply System Level 3 Manager Nancy Grossman FNAL June 28, 2001

  2. Overview of Regulation Needs • 7 Magnet Strings with regulation requirements ranging from 55 ppm to 400 ppm. • 55 ppm means +/- 55 ppm relative to the flattop operating current (RMS). • V105 string requirement is 60 ppm, close to the tightest requirement. • Discussion will center around simulations of the V105 string. • 3 sources of current variation for magnet strings: • 720 Hz power supply voltage ripple being applied to the magnets. • Line voltage changes. • Load changes. Simulations of a particular power supply (or series of power supplies) can be used to see the effects of these changes on the resulting flattop current.

  3. 720 Hz Ripple Effect • 720 Hz line ripple effect on the PS currents is shown in the table below. • Not acceptable • Need filters for each string • Refurbish existing filters • Have costed 3, have claimed 7 for NuMI. • Estimated cost to remove, refurbish and install: ~$10k/string (extra $40K)

  4. Line Voltage and Load Changes Simulations were run for the NuMI V105 string, assuming a constant reference voltage. • 5% change in line voltage was easily corrected for at the level of ~25 ppm with standard voltage regulation. (most variation one would expect) • 5% load change (resistance) gave a 240 ppm current variation. • Corresponds to about a 100 C change in the copper in the magnet or the LCW changing 150C • Other magnet strings would have similar results most likely. • Not acceptable. • Need additional regulation. • HOLEC transductor ($5K/string) • Special FNAL regulation electronics ($5K/string) • Both are designed and installed in the Main Injector • This combination of electronics would give another factor of 2 120 ppm

  5. Line Voltage and Load Changes Three strings are still above the required specifications. So now what?

  6. Additional Factor of 2 - 4 Bandwidth • Each string will be tuned for maximum bandwidth. • 20 Hz is assumed in the previous calculations. • 40 Hz is frequently achieved (but not guaranteed). • Gives a factor of 2 in current stability. Auto-tune • Load changes are typically slow changes and thus Auto-tune can correct for these. • One could then argue why do you need the extra power supply regulation too? • Auto-tune does not always work. • Needs beam and working beam position monitors to work. • Assumes next beam pulse like the previous one. • Experience at FNAL where significant beam control is needed says do both. • Since the power supply regulation is also driven some by groundwater concerns, we want something that is always working.

  7. Other Primary Beam Power Supplies • Quadropole power supplies (20 KW PEI’s): • Standard regulation is at +/- 0.05% of the maximum current (100 or 200 amps) • Corresponds to up to +/-0.44% variation in operating current. • Believed to be sufficient. • Main Injector Trim Magnet power supplies: • Standard regulation is at +/- 0.1% of the maximum current (15 amps) • Believed to be sufficient.

  8. Summary • NuMI power supply regulation levels will be achieved by: • Filters on all 7 strings. • HOLEC and FNAL Electronics on all 7 strings. • Auto-tune. • Tuning for maximum bandwidth. • Cost increase to NuMI: • ~$40k for 4 additional filters (refurbished) • ~$70k for 7 sets of HOLEC/regulation electronics (one for each string) • Other slightly less expensive (and perhaps more effective) options may be designed by Fermilab before NuMI runs, in which case we would certainly use them. • Studies in the Main Injector P1 line will also help us to better define the level of regulation one obtains with a HOLEC transductor and special regulation electronics.

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