ULDB CREAM Monthly Status Report Electrical Power System
ULDB CREAM Monthly Status Report Electrical Power System Arturo A. Vigil Electrical Systems Branch / 569. W Electrical Power System Product Design Lead & Team Leader for the Instrumentation Engineering Team Arturo. A. Vigil. 1@gsfc. nasa. gov 757 -824 -1278 October 1, 2003
Brief History While conducting system level test with TRACE units, discovered that TRACE units did not function as advertised and as expected. Bus voltage was exceedingly noisy and unstable. Based on outcome of meetings from the project, SE, and AETD, we have two design options and are pursuing two parallel paths of development. October 1, 2003 2
Buck Regulator Option 1. Buck Regulators to maintain set bus voltage by shunting excess solar power through shunt resistor(s). 1. Use of existing harnessing into and from our Power Distribution Box. 2. PDB maintains its design maturity. 3. Thermal consideration & mechanical locations. 4. Requires the use of shunt resistor(s). 5. Required harnessing from PDB to buck regulator(s) and from buck regulator(s) to shunt resistor(s). 6. Deals with excess power at the bus end. October 1, 2003 3
MEER Instrument Option 1. MEER Instruments approach. Automatically open circuit solar panels depending on load current demand to maintain set bus voltage. 1. New design. 2. Thermal consideration. 3. No shunts required. 4. Deals with excess power at the front end. 5. May require additional harnessing for monitors to stacks. 6. Replaces original Power Distribution Box. October 1, 2003 4
Buck Regulator Status Received schematic and buck regulator prototype from Jack Shue. Testing unit to better understand verify its operation. 1. Have worked closely with Jack to tweak components on regulator to improve efficiency. 2. Waiting on PCBs to begin populating Buck Regulator and test to verify operation and determine regulators efficiency. 3. Plan to do a functional test on the regulator. A system level test performed with solar array simulators, controllers, batteries, and variable load. At this time, we have prototype connected to power supply, electric load, and shunt resistor. Bus voltage set to 33 volts. Have monitored bus voltage stability and calculated efficiency of 93%. October 1, 2003 5
MEER Instruments Approach Status 1. Built a two string MOSFET circuit and performed a basic functional test with one controller & battery, and a variable load to verify bus voltage set limit and stability under various loads. 2. Expect to have box built on 10/4. 3. Circuit schematic been sent to QSS for simulation and received preliminary report with “Electrically the circuit appears to work very well” on simulations that has been done so far. 4. Upon completion of box, will perform electrical check out, functional test and system level test consisting of connecting controllers, batteries, solar simulators, and variable loads. 5. Measure bus stability, noise, heat dissipation, and efficiency. October 1, 2003 6
Issues 1. Potential 2 V 10 ms spike per spice simulation on both design approaches. Investigate during actual testing. If real, will mitigate with additional circuitry. October 1, 2003 7
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