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<strong>Power</strong> <strong>Distribution</strong> <strong>Unit</strong><br />
SPACE<br />
Based on the requirements for the ESA Small Geo<br />
platform <strong>Terma</strong> has developed and qualified the <strong>Power</strong><br />
<strong>Distribution</strong> <strong>Unit</strong> (PDU) with the following properties:<br />
• Designed for regulated 50 volt bus<br />
• Low mass of 16.3 kg<br />
• High power transfer efficiency<br />
The unit is built in the power module technology developed<br />
by <strong>Terma</strong> for the Galileo spacecraft. It comprises of the<br />
following module types:<br />
• (2) Equipment <strong>Power</strong> <strong>Distribution</strong> (EPD)<br />
• (8) Heater <strong>Power</strong> <strong>Distribution</strong> (HPD)<br />
• (2) Pyro Firing Drive (PFD)<br />
• (2) Thermal Knives Actuation (TKA)<br />
• (2) Command and Monitoring (CM)<br />
• (1) Back plane module<br />
The PDU provides two parallel interface connectors for<br />
upstream power bus connection, supported by an internal<br />
bus capacitor bank to compensate the external bus harness<br />
impedance and to ensure low bus impedance.<br />
The power bus is provided to external interfaces by the<br />
protected power distribution functions, for spacecraft<br />
equipments, heater, pyro firing and thermal knives activation.<br />
All PDU functions can be commanded and monitored via two<br />
independent dual MIL-STD-1553 interfaces. All adjustable<br />
control parameters, protections and switch function settings<br />
can be uploaded and reset from ground control.<br />
Each of the applied power modules is a self contained<br />
function able to initialize and start up when bus power is<br />
available. The system will recover autonomously from any<br />
single point failure without any bus power interruption.<br />
References:<br />
• One unit is to go onboard Hispasat, which is to be<br />
launched in 2012.<br />
Small Geo <strong>Power</strong> <strong>Distribution</strong> <strong>Unit</strong> Flight Model<br />
Space Engineering and Knowledge
Specifications:<br />
Dimensions (L x W x H)<br />
425 x 285 x 160 [mm]<br />
Mass<br />
13.2 kg<br />
Reliability 15 years > 0.990<br />
Bus voltage<br />
50V regulated<br />
<strong>Power</strong> distribution capability<br />
up to 1000 watt<br />
Idle power consumption<br />
< 11.4 watt<br />
Equipment <strong>Power</strong> <strong>Distribution</strong> lines 32<br />
Load current classes<br />
0.5, 1.0, 2.2 and 5.0 A<br />
Heater <strong>Power</strong> <strong>Distribution</strong> lines 128<br />
Load current<br />
up to 5.0 A<br />
Pyro Firing Drive lines 2 x 23<br />
Firing current<br />
5.5 ampere<br />
Thermal Knives Actuator lines 2 x 12<br />
Activation voltage<br />
21.3 volt<br />
DMS Interface<br />
2 x Dual MIL-STD-1553<br />
Temperature<br />
-30°C to +65°C<br />
Equipment <strong>Power</strong> <strong>Distribution</strong> #2<br />
Equipment <strong>Power</strong> <strong>Distribution</strong> #1<br />
32 x LCL / FCL<br />
16 x LCL / R-LCL<br />
Switch<br />
Switch TM<br />
TM<br />
16<br />
16<br />
Equipment<br />
LCL/FCL’s<br />
Dual<br />
Dual CM I/F<br />
CM I/F<br />
Heater <strong>Power</strong> <strong>Distribution</strong> #8<br />
Heater <strong>Power</strong> <strong>Distribution</strong> #2<br />
Heater <strong>Power</strong> <strong>Distribution</strong> #1<br />
Group 2<br />
Group 1<br />
Group LCL<br />
Group LCL<br />
8 x Transistor<br />
8 x Transistor<br />
Switch<br />
Switch<br />
16<br />
Heater<br />
<strong>Power</strong> Lines<br />
50V<br />
Main<br />
Bus<br />
2<br />
Dual<br />
CM I/F<br />
Sw<br />
Sw<br />
TM<br />
TM<br />
Pyro Firing Drive #B<br />
Pyro Firing Drive #A<br />
DISTR<br />
BUS<br />
CAP.<br />
50V Main Bus<br />
Arming<br />
Switch<br />
Current<br />
Regulator<br />
23 x<br />
Selection<br />
Switch<br />
23<br />
Pyro Firing<br />
Lines<br />
Dual<br />
CM I/F<br />
Timing<br />
Thermal Knife Actuator #B<br />
Thermal Knife Actuator #A<br />
Arming<br />
Switch<br />
DC/DC<br />
Voltage<br />
Regulator<br />
12 x<br />
Selection<br />
Switch<br />
12<br />
Thermal Knife<br />
Actuators<br />
Group LCL<br />
Dual<br />
CM I/F<br />
CM I/F #B<br />
CM I/F #A<br />
DUAL CM INTERFACE BUS<br />
Command & Telemetry<br />
Handling<br />
Local<br />
Aux<br />
Supply<br />
BUS<br />
I/F<br />
Discrete<br />
Command &<br />
Telemetry<br />
I/F<br />
Dual Mil-1553<br />
Dual Mil-1553<br />
Discrete TC/TM<br />
Small Geo <strong>Power</strong> <strong>Distribution</strong> <strong>Unit</strong> Functional Schematic<br />
<strong>Terma</strong> A/S Space<br />
www.terma.com
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