# Presentation: 779493

## Section 18

***Power***

*** ******Allan Billings***
*EO-1 Power Lead, Swales Aerospace, Inc.*
***Vickie  Moran***
*GSFC EO-1 Power Lead*
***Ralph Sullivan***
*Power Consultant to Swales Aerospace, Inc.*

## Power System PSR Outline

***Power System PSR Outline***

***Power Mission Element Response***
***Redbook Candidate***
***Power System Readiness***
***Special Topic***

## “As Run” Verification Matrix

## Projected Power On Time

## Power Mission Element Response

***Power Mission Element Response***

***Changes in Verification Matrix---None***
***Configuration Changes---***
***New Version of PSE Software (Version 8.1) installed on 6/23/00.***
***Purpose: To ensure a defined, safe, load condition upon PSE restart.***
***PSE to Load Shed on a Cold Restart.***
***Switchable Loads to be shed:***
*ALI, LAC, X-Band  XMTR, PPT, WARP, Hyperion  Electronics & Cryogenics*
***Switchable Loads to be activated:***
*S-Band XMTR, ACE LVPC, C&DH LVPC, Hyperion Survival HTR, SADE, RWA X, Y & Z Control.*
***Describe Recent Test Results Associated With T/V ******II***
***Power System performed as expected***
***All deviations from expected values were explained in PR’s***
***Thermal Vacuum ******II ******Test Results -- (Following Charts)***
*Includes data trends & test margins*

## Test Results:  Calibration/Characterization

***Test Results:  Calibration/Characterization***

***A trending procedure was run in the background throughout TB/TV capturing the critical Power System telemetry points every 15 sec.***
***The bus voltage, battery voltage, battery current, battery temperature, solar array module current, chassis current, output module #1 current, and output module #2 current  were sampled every 15 sec and compared to the GSE/Umbilical telemetry.***
***All PSE telemetry was in agreement with GSE/Umbilical telemetry to within acceptable limits and the error did not change with temperature or pressure.***
***A special calibration/verification of the half battery voltage differential against the battery GSE was added to the testing since the last thermal vacuum.  As a result, a correction was made to the ground system conversion polynomial to increase accuracy.***
***Additional telemetry was added to the trending procedure since the first thermal vacuum--PSE RSN +15V, -15V, +5V, and battery PRT temperature--just to provide a more complete data book on the power system.***
***Previous thermal vacuum verified that these telemetry were within red and yellow limits.***
***The PSE was fully characterized in all modes of operation:  full charge/current limited charge, V/T clamped charge, and trickle charge.***

## Significant Test Results For T/V II Test

***Significant Test Results For T/V II Test***

***Key Telemetry Same As Thermal Vacuum #1****** ***
_***	***__***Parameter***_***	******   ******	****** ***_***Actual Range***__***	***__***	***__***Requirement ***_
***	******Battery Voltage******	******	******26.5V < VBATT < 32.8V******	******	******22V<VBATT <35V******Bus Voltage ******	******	******26.4V < VBUSS < 33.1V******	******	******22V<VBUSS <35V******Bus Power (Hot--DCE)******	******Pavg=275W,  Pmax=375W******	******300W average ******	******	******	******	******	******	******	******	******	******Battery Current--(Hot--DCE)******	******ImaxCHG=13A,  ImaxDISchg=-13A******	******18A chg i max******	******Bus Power (Cold--DCE)******	******Pavg=300W,  Pmax=350W******Battery Current(Cold--DCE)******	******ImaxCHG=12A,  ImaxDISchg=-12A******	******18A chg I max******Bus Power Maximum Peak******	******Peak = 520W***

## 	Parameter	   	 Actual Range		Requirement
	Battery Temp Max (Launch)	21.5 deg C 			T<25C
	Battery Temp		6.5 deg C<T<20 deg C		0<T<28C	
	Solar Array Module Temp	-4C<T<53C			-10C<T<60C
VT Setting Desired Did Not Change
Determined that VT4 resulted in 100% SOC only at very end of charge cycle (day). 
V/T 5 resulted in 100% SOC well before end of day and will be nominal setting for mission.
XTE and TRMM (both using the same battery) launched in V/T 5 with no anomalies to date.
A higher V/T level at launch is preferred to enable maximum charging of the battery during the  stressful sun acquisition phase of the mission.
The V/T level can be lowered upon sun acquisition or at any time if desired.

_***	***__***Parameter***_***	******   ******	****** ***_***Actual Range***__***	***__***	***__***Requirement***_
***	******Battery Temp Max (Launch)******	******21.5 deg C ******	******	******	******T<25C***
***	******Battery Temp******	******	******6.5 deg C<T<20 deg C******	******	******0<T<28C******	***
***	******Solar Array Module Temp******	******-4C<T<53C******	******	******	******-10C<T<60C***
***VT Setting Desired Did Not Change***
***Determined that VT4 resulted in 100% SOC only at very end of charge cycle (day). ***
***V/T 5 resulted in 100% SOC well before end of day and will be nominal setting for mission.***
***XTE and TRMM (both using the same battery) launched in V/T 5 with no anomalies to date.***
***A higher V/T level at launch is preferred to enable maximum charging of the battery during the  stressful sun acquisition phase of the mission.***
***The V/T level can be lowered upon sun acquisition or at any time if desired.***

***Significant Test Results For T/V II Test***

## Power Mission Element Response

***Power Mission Element Response***

***Additional Peer Reviews***
***None***
***PSE Failure Free Time (to 7/28/00)***
***433 hours since last FSW load (6/23/00).***
***2553 hours since start of Environmental Test (Since installation on the S/C - 7/31/99).***
***PSE Total Operating Time (to 7/28/00) 3527 hours since last hardware change ***
***No failures of PSE on S/C since 2nd integration into S/C.***
***Open Action Items***
***FSW004----Determine Low Voltage Limit for FDC by Launch - 15 days.  Requires flight battery data which will be available before that time.***
***All RFA’s, PAR’s, PR’s Closed***
***Residual Risk--- One Redbook Candidate ***
***PR 837-20-1 - See following charts***

## Redbook Item

***Redbook Item***

***PR- 837-20- 1:  The PSE LVPC `Load Current Sum’ telemetry point (PLVPCLDI2) tripped its Red-Hi (9A) limit on Day 357, 1999.***
***The event occurred after T/V I at ambient conditions.***
***An  FF value = 19.275A (corresponding to the maximum value of the A/D converter in the RSN) was recorded for 1 sample only.***
***This is the only recorded occurrence of this anomaly in 3527 hours (3.174 * 109 A/D  operations @ 4ms rate).***
***The RH limit tripped for 4 seconds (1 cycle).***
***There was no other indication of an  over-current.***
***Other load-current samples in the 4-second packet (PLVPCLDI1, 3 and 4) were all nominal.***
***The LVPC 8-Ampere over-current limit did not trip.***
***No over-current recorded on the (active) the Umbilical monitor.***

## Redbook Item

***Redbook Item***

***Request for  Action (RFA 33.04), including fault tree analysis completed***
***Following possible sources of the event were investigated:***
***RSN Software --- no explanation found.***
***Hardware --- There is an unlikely possibility that a narrow (<25us) pulse could  generate an FF in the  A/D converter and provide no other indication.***
***FEDS --- Source of the problem was not found at the time of the  RFA***
***Recent Investigation:***
***Currently, there is an investigation into the possibility that  occasional, corrupted data packets might have been received by the ground system.***

## Power System Readiness

***Power System Readiness***

***Statement of Readiness***
***The Power System is Ready for Launch.***
***All required test procedures: complete and released.***
***Solar Array: successfully passed final inspection.***
***Battery handling plan (SAI Proc. 242): complete and released.***
***PSE: thoroughly tested and ready for launch.***

## Special Topic:

***PSE Oscillation***

*** ******Allan Billings***
*EO-1 Power Lead, Swales Aerospace, Inc.*
***Vickie  Moran***
*GSFC EO-1 Power Lead*
***Ralph Sullivan***
*Power Consultant to Swales Aerospace, Inc.*

## Issue

***Issue***

***During S/C simulation testing PWM solar array current was reduced from 4A to 2A to simulate a possible (but unlikely) S/A anomaly.***
***Description of Issue***
***As designed, a reduction of the PWM current to 2A caused the shunts to switch on and off, resulting in a low frequency oscillation in the battery charging current. ***
***This is an expected result.***
***This condition is not likely to occur in orbit.***
***However, there  was some concern that the low frequency oscillation may have over-heated two damping resistors inside the PWM circuit.***

## EO-1 software loaded into MAP PSE ETU. Tests revealed that PWM cycle rate was 41Hz. Voltage waveforms across damping resistors indicated acceptable power dissipation 
R185 = .69W, rated at 3W (1.5W De-rated per PPL-20)
R186 = .89W, rated at 7W (4.2W De-rated per PPL-20)
Thermal analysis assuming 2W (in vacuum) indicated a temperature rise of the resistors less than 15 degrees.
Assuming worst case board temperature of 53 degrees (based on T/V I data), the worst case resistor temperature is less than an acceptable 68°C versus a maximum rated temperature in excess of 125 degC.

***EO-1 software loaded into MAP PSE ETU. Tests revealed that PWM cycle rate was 41Hz. Voltage waveforms across damping resistors indicated acceptable power dissipation ***
***R185 = .69W, rated at 3W (1.5W De-rated per PPL-20)***
***R186 = .89W, rated at 7W (4.2W De-rated per PPL-20)***
***Thermal analysis assuming 2W (in vacuum) indicated a temperature rise of the resistors less than 15 degrees.***
***Assuming worst case board temperature of 53 degrees (based on T/V I data), the worst case resistor temperature is less than an acceptable 68°C versus a maximum rated temperature in excess of 125 degC.***

***Test & Analysis Performed***

## Impact on EO-1 Mission

***Impact on EO-1 Mission***

***There is no impact on the EO-1 mission.***
***An impact is possible only if the the PWM solar array  current is reduced  to the current of the switched shunts  (2A BOL) or less ***
***If this event occurs, the battery charging current will add approximately 2A p-p of low frequency oscillation to the power bus. The PSE can operate indefinitely this way without damage.***

## Conclusions

***Conclusions***

***This condition is not likely to occur in orbit.***
***If oscillations do occur, the PSE will not be damaged. The power system will function and complete the mission with increased noise on the power bus.***
***There is negligible residual risk.***