Transcript ElectricalFinal

Space
Technology
GSFC
5
“Tomorrow’s Technology Today”
Section 7.0
Electrical Systems
Walter S. Bradley
Electrical Systems Engineer
ST5 PDR June 19-20, 2001
GSFC
Agenda
• Requirements
 Documentation
• Grounding Diagram
• Electrical Block Diagram
• EMI/EMC GSE
• Magnetic Control Plan
• Magnetic Budget
• Interconnect List
• Risk Mitigation
ST5 PDR June 19-20, 2001
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GSFC
Key Level I Requirements
• The spacecraft shall not present a hazard to the primary satellite
in the form of EMI/EMC, contamination, etc. (MRD10401000)
–
ST5 is un-powered until after deployment from launch vehicle
–
ST5 is tested for GEVS radiated emissions compliance at the Spacecraft
level
• The spacecraft shall be powered-on upon separation from the
deployment structure. (MRD10404020)
–
The PSE Power Bus Enable Switch is activated when the ST5 zero force
flyaway connector is separated during ST5 deployment from the deployment
structure
ST5 PDR June 19-20, 2001
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Key Level II Requirements
• The spacecraft shall be designed so that generated electric
and/or magnetic fields do not interfere with magnetometer
measurements. (MRD20102010)
–
Electrical Requirements Specification (ST5-495-016) and Magnetic Control
Plan (ST5-495-058) provide design constraints, material selection criteria,
and test programs to assure compliance
• The spacecraft generated magnetic field at the magnetometer
sensor head shall be less than 0.1 nT from DC to 0.1 Hz and less
than 0.05 nT for frequencies between 0.1 Hz and 200 Hz.
(MRD20102011)
–
Magnetic characterization and tabulation of all S/C parts, strict control of
current loops, and final magnetic test of S/C will verify compliance
ST5 PDR June 19-20, 2001
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GSFC
Requirements to Subsystems (1 of 2)
• Surface Conductivity
–
10^9 Ohms per square
• ESD and Deep Dielectric Discharge protection
–
TVS devices to chassis at Subsystem interfaces
• Current Loop Minimization
–
Solar Array Panel Wiring
–
Battery wiring
–
Power flow control on PWBs by trace mirroring, isolation
–
Twisted wires in harnesses
–
High impedance interface circuitry for signal communication
–
Connector pin assignment (power in center)
• Deep Dielectric Discharge Protection
–
TVS at each end of wire, Microsemi or Harris
ST5 PDR June 19-20, 2001
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GSFC
Requirements to Subsystems (2 of 2)
• EMI/EMC (typical levels)
–
Inrush currents - <100% nominal for 50mS
–
Common Mode currents - <1 uA
–
Transient operation – 150% of nominal I
–
Voltage ripple – 0.1Vp-p@5V, [email protected]
• Magnetic Materials Selection Criteria
–
Listed in Magnetic Control Plan
–
Test and Documentation requirements
• Chassis connection or isolation
• Grounding
–
Signal ground
–
Power ground
–
Leakage currents, Isolation resistance
ST5 PDR June 19-20, 2001
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GSFC
Harness Requirements (1 of 2)
• Connector Specification
–
Nonmagnetic, MIL-C-83513 or GSFC S-311-P-4/07
–
Minimum size to ease assembly, access
• Wiring Control
–
Twisted pairs for differential signals, Twisted quads for power
–
Power and Signals in same connector for Magnetic field control
–
Overall shield connected to chassis at each end
• Derating Criteria
–
Wires and connector contacts derated per PPL-21
• Harness Mockup as Design Aid
–
Harness lengths
–
Mechanical clearances
–
Access for assembly, test, repair
ST5 PDR June 19-20, 2001
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GSFC
Harness Requirements (2 of 2)
• Quality
–
Build, Test, and Inspect to established ISO procedures
• Delivery schedule
–
FlatSat Breadboard Integration & GSE
October 2001
–
FlatSat ETU Integration
April 2002
–
ST5 Flight and Spare
August 2002
–
Environmental GSE
January 2003
–
Launch Support GSE
August 2003
ST5 PDR June 19-20, 2001
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GSFC
Documentation
• Specifications
–
Electrical Requirements (ST5-495-016) preliminary version released
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Interface List (ST5-495-059) updated version on ST5 web site
–
Harness Specifications - in ST5-495-016
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Harness Drawings and Mockup - in design
• Budgets
–
Electrical: power, inrush, noise, radiation - in ST5-495-016
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Magnetic: materials, currents - in ST5-495-058
• EMI/EMC performance
–
Specifications and Plan - in ST5-495-016
• Magnetic performance
–
Magnetic Control Plan (ST5-496-058) preliminary version released
–
Testing to characterize parts
ST5 PDR June 19-20, 2001
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GSFC
Grounding Diagram (1 of 2)
• Single point ground in EPS
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PSE Card - to S/C chassis through “Cardcage” Backplane
–
Star ground from EPS single point ground
• Subsystem chassis connected to S/C structure
–
High frequency noise containment
–
Circuit grounds isolated from chassis
• RF chassis isolated from S/C structure
–
Circuit (RF) grounds connected to subsystem chassis
• Overall harness shield
ST5 PDR June 19-20, 2001
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GSFC
Grounding Diagram (2 of 2)
ST5 PDR June 19-20, 2001
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Electrical Block Diagram (1 of 2)
• EPS Overview
–
Solar Array Panels
–
Battery
–
Regulators and Switches
–
Power Services, 5 Volt regulated and 7.2 Volt unregulated
• Signal Flow
–
Digital type and direction

Data

Command

Telemetry, Status
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Differential or Single Ended
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Analog telemetry
• C&DH/PSE “Cardcage”
ST5 PDR June 19-20, 2001
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Electrical Block Diagram (2 of 2)
ST5 PDR June 19-20, 2001
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EMI/EMC GSE
• ST5 Unique Test Equipment
Power
Supply
Electronics
Card
Simulator
Noise Injection
Simulator
Load Switching
Simulator
UNIT UNDER
TEST
Inject commonmode current
Draw pulse currents,
average currents, transient
currents
Verify operation during
test
- Use GSE at Subsystem level to characterize conducted EMI/EMC compliance
- Test for Noise and Transient Compatibility
- Install Subsystem at S/C when EMI / EMC compliance verified
• Radiated Emissions and Susceptibility per GEVS @ S/C level
ST5 PDR June 19-20, 2001
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GSFC
Magnetic Control Plan
• Magnetic Control Plan, Budgets, and Test Data
–
System Description and Magnetic Requirements
–
Magnetic Moment Allocations from Materials
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Magnetic Moment Allocations from Circuits
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Derived Requirements Imposed by Allocations
–

Materials selection

Parts selection
Magnetic Screening, Degaussing, Characterizing Plan

Part level

Subassembly level

Spacecraft level
–
Magnetic Control During I&T
–
Tabulation Report
ST5 PDR June 19-20, 2001
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GSFC
Magnetic Budget (1 of 2)
• Material Allocation
–
Total Mass of Subassembly
–
Location of Subassembly
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Material Properties Contributing to B Field Variation
• Circuitry Allocation
–
Current Loop Control by Design of Card Traces
–
Current Loop Control in Solar Panel Wiring
–
Current Loop Control in Harness Design
–
Parts Selection
• Spacecraft Allocation
–
Eliminate Ground, Structure Currents
–
Material Selection
ST5 PDR June 19-20, 2001
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Magnetic Budget (2 of 2)
• Tested RF isolators, Thruster valve, Springs, and Battery
• Static and Dynamic Allocations and Budgets
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Interconnect List
• Hardware Compatibility
–
Driver / Receiver
–
What is Power Flow when Subsystem OFF
–
Is this an EMI/EMC source
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Is this a Current Loop Source
• Signal Compatibility
–
Speed
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Voltage / Current levels
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Impedance
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ESD Susceptibility
• Harness Design
–
Connectors
–
Wiring
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Interconnect List - Sample
ST5 PDR June 19-20, 2001
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Risk Mitigation
• Risk: Magnetic Cleanliness (Meeting Specification Limits)
• Risk Mitigation:
–
More detailed analysis and modeling
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More thorough magnetic testing and characterization
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Specification relief
–
Compensation magnets or current loops
ST5 PDR June 19-20, 2001
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