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ESA Document - Emits - ESA

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3.3.4.3.3 Power conditioning and distributing<br />

HMM<br />

Assessment Study<br />

Report: CDF-20(A)<br />

February 2004<br />

page 187 of 422<br />

To limit the harness losses a higher voltage should be chosen, typically 120V. Nevertheless, this<br />

voltage cannot be too high otherwise there is a risk of electrocution of the crewmembers and also<br />

to avoid plasma interactions on the solar wings.<br />

Due to the large amount of power units, a regulated topology shall be selected.<br />

90% is the efficiency assumed for the Battery Charger Regulator.<br />

85% is the efficiency assumed for the Battery Discharge Regulator.<br />

For safety reasons, the Power Conditioning and Distributing has to be double-failure tolerant:<br />

• First failure: the spacecraft shall remain fully operational<br />

• Second failure: the spacecraft shall still be operational with possible limitations on the<br />

mission.<br />

For safety, an architecture with separated and identical power systems with crosstraps to the<br />

different units connected on the bus is proposed. Each power system is composed of a dedicate<br />

solar panel, a battery module, a power conditioning and distributing unit. Compared to the power<br />

required, one power system is added in the design to cope with possible failures.<br />

3.3.4.4 Baseline design<br />

3.3.4.4.1 Budgets<br />

Solar wings<br />

Solar wings<br />

2 power<br />

module<br />

2 power<br />

module<br />

Figure 3-44: Power system overall architecture<br />

There are two separate power modules in each of the two nodes, as shown in Figure 3-44. Each<br />

power module includes:

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