Electrical Power Interfaces

Power Interfaces to the EPA

At the level of the EXPRESS Pallet Adapter the following are available for payloads:

• - 2 outlets rated at 2.5 kW@ 120 V (total EXPRESS Pallet allocation); or
• - 2 outlets rated at 500 W @ 28 VDC (50% of EXPRESS Pallet allocation); or
• - one of each (with a ceiling of 2.5kW for payloads)

Figure 7.1: Interface concept at EPA level. (tbd)

Interface to Power Distribution Unit (PDU)

The Power Distribution Unit (PDU) will provide 28Vdc and/or 120Vdc as a custom-built unit, according to the final complement of instruments on the EPA. The PDU can connect two or more instruments. The PDU preliminary design and interfaces are shown in Figure 7.2.

Figure 7.2: PDU Interface Concept (Preliminary)

Harness

The specifications for connectors and harness are tbd at this stage. However the following guidelines might be followed:

• harness between PDU and SPLC and instrument will be provided by the integrator;
• Instrument connector part is provided by the payload developer.

Stay Alive Power

Electrical power to payload heaters will be provided during transportation of the EPA in the NSTS Shuttle Orbiter cargo bay and during transportation of the EPA between the cargo bay and the final attachment site on the ITA. A conceptual layout for the Stay Alive Power system is shown in Figure 7.3.

Figure 7.3: Stay-alive Power Concept (Preliminary).

The battery is sized to deliver ±45W for 5 to 6 days. Heaters,to take advantage of this provision and the required switches between normal and stay alive power have to be provided by the user. It is possible that these batteries could be rechargeable, which could allow outages of the ISS power bus during EP operations to be bridged. In this case the payload would need to provide the recharging capability.