Electrical Power Subsystem (EPS)
Next: Solar Array (SAS)
Previous: Reaction Control (RCS)
Up: SAX Home Page
Contents: Table of Contents
It is the SubSystem that performs:
- Energy storage;
- Power conditioning;
- Power switching and distribution to the Satellite Subsystems and
Scientific Instruments.
The EPS includes the following units:
- Power Control Unit (PCU);
- Battery Charge Discharge Regulator (BCDR);
- Power Protection and Distribution Unit (PPDU);
- Battery Control Unit (BCU);
- Battery (BTR) - 2.
Energy storage (465 Wh) and its delivery to the Satellite users during the
Eclipse period (37 min) is performed by a battery system consisting of two NiCd
battery of 36 cells each with a name plate capacity of 30 Ah.
Withstanding of the 13000 charge/discharge cycles required by the
SAX minimum operative life is ensured by limiting
the battery Depth Of Discharge (DOD) to 25%.
The PCU performs the regulation of the power bus voltage (29 V nominal) during
the sunlight period through shunt regulators for each
solar panel main section power line.
The BCDR controls the battery charge/discharge by means of:
- regulation of the power bus voltage during the eclipse when the batteries
are supplying the Satellite;
- Regulation of the battery recharging during sunlight by controlling both
the voltage and current, namely:
- constant current technique up to the End Of Charge (EOC) voltage;
- constant voltage technique (tapering) from the EOC voltage on.
The PPDU provides the power distribution by splitting the different output
lines to the end users and ensures protection against overcurrent by
electronic current limiters.
The BCU performs battery status monitoring (voltage and temperature) and
takes automatic protective actions mainly consisting of:
- entry into power saving mode (disconnection of predefined power lines);
- initiation of the end of charge procedure.
This file was last modified on Wednesday, 02-Sep-1998 17:28:57 CEST
by Mauro Orlandini
Next: Solar Array (SAS)
Previous: Reaction Control (RCS)
Up: SAX Home Page
Contents: Table of Contents