Energy Power System

Electricity

• Electricity is the flow of electrons through a conductor

• Electricity will only move through a closed circuit, if the circuit is broken the flow of electrons stops

Electricity (cont.)

• Voltage - Electric potential or potential difference, provided by the battery, expressed in volts

• Amperage - The strength of an electric current, flows through the conductors to the load, expressed in amperes

• Resistance - Is present in any load, expressed in ohms

Light to Power

• Solar Panels collect sunlight and convert them into electrical power

• For maximum power solar arrays need to be perpendicular to the light rays hitting them.

Orbit Cycle

• During the 30 minute eclipse period the batteries supply power

• While in insolation period the solar arrays provide power while the batteries charge for the next eclipse period

Primary and Secondary power

• Primary power is high voltage power generated at a centralized source

• Before power is delivered to users it is stepped down by a transformer to a set voltage (secondary power)

• Secondary power is then delivered to the user

System Overview

• Internal and external systems– Internal system distributes

secondary power

– External distributes primary power

• 8 identical channels of power (1-4 A/B)– Each channel supplies 100

amps of current

Internal EPS

• Loads, RPDA, SPDA, DDCU, MBSU, ICC

• Converts primary power to secondary power

• Routes secondary power to any internal systems

Loads

• A load is anything that needs electricity to function.

• Computers, Lights, Pumps, etc.• Each load requires a certain current (amps)

which is specific to that device• Not all loads are physically inside the

station, but all are supplied by the same internal distribution network

SPDA/RPDA/DDCU

• Secondary Power Distribution Assembly– Supports a single channel of power

• A is even channel B is odd channel

– Routes power to one RPDA and six loads

• Remote Power Distribution Assembly– Routes power to six loads

• Direct current to Direct current Converter Unit– This is the unit that converts primary power (~160 V

dc) to secondary power (~124 V dc)

MBSU/ICC

• Main Buss Switching Unit– Each support 2 channels of power with a total

of 200 amps– Routes power to two SPDAs

• Interconnecting Cables– Create a bridge for two or more MBSUs to

share power across them

External EPS

• SARJ, IEA, ECU, SSU, PCU, BGA, PVA

• Produces primary power from the solar arrays, and stores power in batteries for eclipse phase

SARJ

• Solar Alpha Rotary Joint

• Rotates 4 channels of power at one time– Controls rotation

parallel to the main station truss

IEA

• Integrated Equipment Assembly

• Battery Charge Discharge Unit (BCDU)– When signaled by the ECU the BCDU begins

charging or discharging the batteries

• Batteries (BAT)– Batteries store power for use during the eclipse

phase of the station’s orbit

IEA (continued)

• Direct Current Switching Unit (DCSU)– Routes power from BGA to batteries, IEA, and

Internal system

• Direct current to Direct current Converter Unit (DDCU) – Provides Secondary power for all components.

IEA Thermal control system

• IEA has a self contained thermal control system for each channel

• Small radiators under each IEA dissipate heat from the SSU as well as batteries and other IEA components

• This system functions in the same manner as the main TCS for the station

• Pump and Flow Control Subassembly (PFCS) and Photovoltaic Radiator (PVR)

ECU/SSU

• Electronic Control Unit– Manages when to charge and discharge the

batteries

• Sequential Shunt Unit– Shunts any excess power generated as heat– Small radiator beneath each PVA radiates heat

Grounding

• To prevent electricity from arcing across the station all electrical devices are grounded to the main truss.

• Plasma Contractor Unit (PCU)– Emits a stream of plasma to ground the space

station’s main truss to space– Prevents arcing to any external spacecraft

during docking or EVA

BGA/PVA

• Beta Gimbal Assembly– Rotates one channel of power per BGA– Controls rotation perpendicular to the main

station truss

• Photovoltaic Array– Collects sunlight and converts it into electrical

power

Warning Signs of a SOBE

• Red indicator light on the system wall

• Loss of Power (I.e. lights or computer unexpectedly shut down)

• Warning through HAL or other system

• Contingency of another SOBE

Things to check during a SOBE

• For maximum power the panels must be perpendicular to the sunlight, if misaligned they may not produce enough power

• There are many points were power can be stopped, be sure to check them all