Status date

More than ever, the telecom Geo satellites industry is facing a highly competitive market, where the technical and cost performances have to be improved constantly.

The existing Alcatel ETCA PCU products (dedicated to the Alcatel SPACEBUS platforms) are the SPACEBUS 3000 PCU (from 2kW to 5.4 kW at 50V) and SPACEBUS 4000 PCU (from6kW to 21 kW at 100V). However, in its low end (from 6 to 15kW), the SB4000-PCU is not optimised due to the impact of the non-modular functions which are dimensioned for the full power (connections, battery charger, bus capacitor and the solar array regulation module).

In the frame of the common Alcatel-Astrium @BUS platform, a new generation of PCU shall be developed in order to improve its competitiveness in terms of mass, efficiency, power modularity and above all cost. Optimisation shall be performed in the nominal @Bus power range (13 to 19 kW), but extension from 8 to 26 kW shall be analysed. In addition, retrofit to the present Alcatel platform (SB4000) and Astrium platform (EUROSTAR 3000) shall be also investigated as far as possible.

The design and development of the SRU will be based on the SB4-PCU experience, but with important upgrades (design to cost activity mainly based on the design rules simplification, new generation of power components, topologies review, update of the environment constraints., & ) in order to meet the following objectives:

click for larger image

  • Improvement of the Conductance Susceptibility bus performances (including higher TDMA load modulation)

  • Compatibility with the new mult

Not Applicable.


See the project objectives.


The baseline to supply the satellite equipments is a full regulated bus at 100V using solar array sources during sunlight periods and single (at low power) or two Li-Ion batteries during eclipse periods. This architecture is similar to the SB4000 architecture.

The electrical design of the SR is classically constituted by the following sub-functions:

  • Power input/output interfaces (batteries connections, SA sections connections, main bus distribution, AIT facilities).

  • SA power regulation under S3R concept.

  • Batteries discharge regulation (BDR), realised by several DC/DC converters in parallel. The topology of the converter is still TBD (HE-Boost, Super-Boost, Add-On Cûck, simple Boost).

  • Batteries charge regulation, two alternative concepts are envisaged:
    - like BDR, several DC/DC converters (buck or super-buck topology) in parallel,
    - direct connection of several SA sections to the batteries under S4R concept (or alternative version).

In addition, the SRU assumes the charge management (charge current control, EoC regulation, warnings activation) under OBC responsibility.

  • Main Error Amplifier (MEA), assuming the energy sources management (with priority to SA) and activates the batteries recharge after each eclipse or after batteries peak power demands.

  • Main bus filter, realised by self-healing capacitors .

  • Auxiliary power supplies (APS) delivering specific voltages to the SRU internal low-level.

  • TM/TC interfaces which centralise digital and analogue commands and measures before dialogue with the OBC through reliable serial link (1553 protocol) or specific direct lines.

Not Applicable.

Current status

The predevelopment has been completed by the Architecture Review held end of June 2004.