# Presentation: 419789

## 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).
- 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.  **

## 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)**

## 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)**
**_x0008_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**

## Line Voltage and Load Changes

**Three strings are still above the required specifications. **
**So now what?**

## 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.

## 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.

## 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.**