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X-ray Wide Field Imager

X-ray Wide Field Imager. Electrical Power System Bob G. Beaman 16 – 20 April, 2012. Subsystem Agenda. System Summary Block Diagram Load Analysis EPS Curve Slew and Communication events Issues / Potential Risks / Future work EPS Summary EPS Trade Acronym List. Subsystem Summary.

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X-ray Wide Field Imager

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  1. X-ray Wide Field Imager Electrical Power System Bob G. Beaman 16 – 20 April, 2012

  2. Subsystem Agenda • System Summary • Block Diagram • Load Analysis • EPS Curve • Slew and Communication events • Issues / Potential Risks / Future work • EPS Summary • EPS Trade • Acronym List

  3. Subsystem Summary • Electrical Power System Summary • Solar Array. TjGaAs at 28% efficiency, cosine angle 30 deg for Instrument off pointing. One extra strings for reliability. SpenvisPmax 1.814E+14 used for the solar array degradation. Solar array temp assumed to be 72 deg C. • Battery. Sized for the launch power loads. This design assumes 60 min from launch (spacecraft on battery power) to acquiring the sun and being power positive with a 35% DOD. Battery Power on Safe Hold will last about 79 min with no solar array power, longer if solar power is available. The Battery is internally redundant and will function to meet EOL requirement with one failure. • Power System Electronics (PSE). A independent PSE is assumed. The PSE will have redundant components to meet the class C redundancy/reliability requirements. Fully redundant power feeds are provided for loads that need redundancy. • Harness. Harness is calculated based on a percentage of power sizing between the S/A, battery and PSE.

  4. Electrical Power Block Diagram I T T I I 1553 1553 I/F Special Commands Special Commands Test/Umb I/F FPGA Controller PSE Specific H/W Test/Umb I/F & PSE Specific Software FPGA Controller PSE Specific H/W Local Temp I/F & PSE Specific Software Local Temp I/F Double Insulated Bus Solar Array Module Output Output Output Module Module Module Battery Backplane/ Bus Cap X8 Battery Battery Module Module X2 Control Module Control Module BGB 100804

  5. Load Analysis

  6. EPS Curve One extra solar array string for reliability

  7. ACS Slew & Communication Power • To cover the ACS slew, power may be needed from the battery. Load Analysis Slew Maneuver Mode requires 1132.8 watts. The solar array will need to deliver 1255.8 watts with current EPS losses*. The EOL Solar Array power needs to meet 1044.1 watts. The difference 211.7 watts needs to come from the battery. The current needed is 211.7/28v=7.56 amps. The 40ah battery, 40/7.56=5.29 hours or 317 min. This is more than enough time for the power system to support this maneuver. • To cover the Communication, power may be needed from the battery. Load Analysis Comm Mode requires 1000 watts. The solar array will need to deliver 1109 watts with current EPS losses*. The EOL Solar Array power needs to meet 1044.1 watts. The difference 65 watts needs to come from the battery. The current needed is 65/28v=2.32 amps. The 40ah battery, 40/2.32= 17.3 hours. This is more than enough time for the power system to support this Comm down link. *this calculation is bases on EOL solar array power. During earlier times, depending on the season, the solar array may have ample power and no battery discharge is needed.

  8. Issues / Potential Risks / Future work • Issues • Risk • Future Work. • Load Profiles could be developed to further define battery operations during a Communications event and during ACS maneuvers. • Since the power is around 1,000 watts, it may be possible for future avionics equipment to incorporate the power system equipment. This would reduce cost and mass.

  9. EPS Summary

  10. EPS Trade * Does not include a iteration from any subsystem or the instruments.

  11. Acronym List PSE Power System Electronics DOD Battery Depth of Discharge SA Solar Array SAD Solar Array Drive EOL End of Life Ah Ampere hours TjGaAs Triple Junction Gallium Arsenide M Meters M2 Meters Squared Kg Kilograms deg Degree, Temp or angle depending on use LiIon Lithium Ion Battery

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