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SNS Power Supply Control

Sheng Peng

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Overview

Power supplies are from different vendors» IE power, Danfysik, Alpha …

Power supplies have different capability» +/- 20 Amps, +/- 35 Volts stackable» +525 Amps, +35 Volts» +400 Amps, +20 Volts» +375 Amps, +80 Volts» +390 Amps, +24 Volts» +700 Amps, +18 Volts» +900 Amps, +51 Volts» +1300 Amps, +95 Volts» +1405 Amps, +390 Volts» +4000 Amps, +18 Volts» +6000 Amps, +440 Volts» +185 Amps, +27 Volts» +1400 Amps, +800 Volts» +2200 Amps, +33000 Volts» +20 Amps, +75 Volts» +40 Amps, +75 Volts» …

Uniform control interface for most of power supplies» SNS Power Supply Controller (PSC)/Power Supply Interface (PSI)» EPICS based software

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Revisons

PSC» 6U single wide VME board for operation» 1U rack mounted for PSI test and calibration» PSC based function generator (RHIC only)

PSI» 1U rack mounted for rack mounted/standalone power supply» 6U single wide VME board for VME-style power supply» “Higher speed less ADC” PSI (Under development in RHIC)

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Power Supplies in SNS

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Automated Power Supply Test and Calibration

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PSC/PSI Software

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PSC/PSI Hardware

PSI and VME with CPU and PSC

PSC

PSI

CPU

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PSI

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PSC/PSI in SNS

PSC/PSI is the SNS standard interface to every power supply

PSI (Power Supply Interface)» Installed with every power supply» One 16-bit DAC with jumper selectable Unipolar/Bipolar mode» Four 16-bit ADCs» Self calibration» 15 bits digital out with selectable static or 100ms pulse mode» 16 bits digital in» Fiber link to PSC, 9-pin analog connector/37 pin digital

connector to power supply PSC (Power Supply Controller)

» Customized VME board with serial port available» Fiber link to PSI» Support 6 power supplies per board» 128K circular buffer per channel to save 5458 samples» Software or hardware triggered read/write up to 5KHz» Burst read up to 10K samples/second (BNL is upgrading it to

100K)

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Communication Protocol/Real-time performance

CPU PSC» Communicate thru VME bus backplane» All registers are memory mapped» Large circular buffer holds read back» Typical VME access cycle is 0.5~1.0 µs/word

PSC PSI» Multimode fiber with SC connector» 5MHz carrier, upgradeable to 50MHz» Each frame consist of 1 start bit, 1 byte frame ID, 3 bytes data,

1 byte CRC and 2 stop bits. So 43bits(8.6µs)/Frame in total.» Setpoint/command needs only 1 frame (plus 1 echo)» Readback needs 7 frames (1 request, 6 response)» Whole write action takes ~20µs (include DAC setup time)» Whole read action takes ~80µs

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Portable Power Supply Test Stand

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Long Term Reliability Test Stand

Each VMEHas 4 PSC’s

Each RackHas 24 PSI’s

Running at up to 4000Hz for several months

Many 10^12 messages without CRC or timeout errors.

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Electrical performance (Some test results)

Fiber interface provides the best electrical isolation ADC Reading Accuracy

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Some Test Results ADC Linearity Test

» Approximately 1-bit (300uvolts) variation from –10v to +10v input.

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Some Test Results

ADC Temperature Stability

300uvolts = 1 bit

Approximately ½ bit change with 10 degree F change in temp.

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Cost

There are two choice to get PSC/PSI» Buy as COTS from Apogee Labs» Get design then have a manufacturer to build it

PSI» RHIC built it recently with a small amount: $895 each» RHIC built revised PSC with a small amount: $1600 each» Apogee Labs ask for $2854.50 (~$2000 for BNL) per board

with the order more than 100 boards» Assume we buy PSC from Apogee Labs and build PSI like

RHIC did, the cost will be $895 + $2854.50/6 = ~$1380/PS» If we build PSC too, the target cost should be ~$1150/PS

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Status

In use at NSRL and SNS» DC power supplies 100ppm accuracy» 60Hz triggered read/write

Preliminary use at IHEP» planned for BEPC-II

Under evaluation for other BNL applications

Design owned by BNL

EPICS S/W freely available

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Summary

PSC/PSI combination can be a cost-effective solution

H/W is proven reliable

H/W design is “open”

EPICS S/W is available

User community is growing