# Power processing unit

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{{Short description|Component responsible for regulating electrical power}}
{{confused|Power Processing Unit}}
{{More citations needed|date=April 2020}}
A '''power processing unit''' ('''PPU''') is a circuit device that convert an electricity input from a [utility line](/source/utility_power) into the appropriate [voltage](/source/voltage) and [current](/source/electric_current) to be used for the device in question.  They serve the same purpose as [linear amplifier](/source/linear_amplifier)s, but they are much more efficient, since the use of linear amplifiers results in much power loss due to the use of a [resistor](/source/resistor) to change the voltage and current.  Instead of using a resistor, PPUs use [switch](/source/switch)es to turn a signal on and off quite rapidly in order to change the average current and voltage.  In this way, they could be conflated with [DC-AC converter](/source/DC-AC_converter)s, but the frequency at which they switch the signal on and off is a few orders of magnitude higher than that of AC signals. They are used to convert the current and voltage of both [direct current](/source/direct_current) (DC) and [alternating current](/source/alternating_current) (AC) signals.<ref>Ned Mohan. ''Electric Machines and Drives: A First Course.'' Minneapolis: John Wiley and Sons, 2012</ref>

==Spacecraft==
In the context of [spacecraft](/source/spacecraft), the power processing unit (PPU) is a module containing the [electrical](/source/electrical) subsystem responsible for providing [electrical power](/source/electrical_power) to other parts of the spacecraft.  The PPU needs to be able to cope with varying [demands](/source/dynamic_demand_(electric_power)) for power output and provide that power in the most efficient manner possible.

There are two main constraints placed on PPUs:

* [Power generation](/source/Electricity_generation) from, for instance, a [solar array](/source/photovoltaic_array) or [radioisotope thermoelectric generator](/source/radioisotope_thermoelectric_generator) where power generation can vary based on external conditions.
* [Power utilization](/source/Isoelastic_utility), which varies depending on the current internal activities performed by the spacecraft such as burst [radio transmission](/source/radio_transmission) or external demand factors like outside temperature and the need to provide heat to maintain constant internal temperature.

Major considerations in building PPUs are [weight](/source/weight), [size](/source/measurement) and [efficiency](/source/efficiency).<ref name="The Future is NEXT in Ion Propulsion">{{cite web|url=http://www.inspacepropulsion.com/FactSheets/EP%20Fact%20Sheet.pdf|title=The Future is NEXT in Ion Propulsion|access-date=2008-10-13|archive-url=https://web.archive.org/web/20081120170028/http://www.inspacepropulsion.com/FactSheets/EP%20Fact%20Sheet.pdf|archive-date=2008-11-20|url-status=dead}}</ref>
<ref name="NASA report">{{cite journal|url=https://arc.aiaa.org/doi/10.2514/6.2004-3453|title=An Overview of the High Power Electric Propulsion (HiPEP) Project|date=July 2004|first1=Fred |last1=Elliott|first2=J. |last2=Foster |first3=M. |last3=Patterson|journal=40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit|doi=10.2514/6.2004-3453 |isbn=978-1-62410-037-6 |access-date=January 15, 2023|url-access=subscription}}</ref>

Most PPUs process and supply [direct current](/source/direct_current) because that is what is generated by a solar array.

The PPU is also responsible for [voltage](/source/voltage) conversion and supplying the required voltage to other subsystems of the spacecraft.

== References ==
{{reflist}}

Category:Spacecraft components
Category:Electrical engineering

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Adapted from the Wikipedia article [Power processing unit](https://en.wikipedia.org/wiki/Power_processing_unit) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Power_processing_unit?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.