Jalbert
Topic Author
Posts: 2
Joined: Tue Jan 10, 2017 12:50 pm

787 Large Motor Controllers

Fri Mar 03, 2017 9:41 am

Hi all.
Can anyone give a brief explanation of these.I am told they are "like large liquid cooled TRUs".
However they seem a bit more manly than that given they're dedicated to the heavy 270 volt loads?
Thanks in advance.
 
BravoOne
Posts: 1664
Joined: Fri Apr 12, 2013 2:27 pm

Re: 787 Large Motor Controllers

Sun Mar 05, 2017 1:38 pm

These are liquid cooled through the Power Electronics Cooling System, better known as the PECS system. Pronounced PEECEEs. It is part of the Integrated Cooling System.

The Large Motor Distribution System handles the large loads and it uses a 235Vac electrical power supply. Frankly the system is very complicated and way beyond the average pilots electrical system knowledge so consequently you just accept the fact that it works and forget trying building the system, much less explaining it in detail. Even the Boeing FCOM does not go into detail on this subject.
 
User avatar
7BOEING7
Posts: 2471
Joined: Fri Oct 12, 2012 5:28 pm

Re: 787 Large Motor Controllers

Wed Mar 08, 2017 4:18 pm

BravoOne wrote:
These are liquid cooled through the Power Electronics Cooling System, better known as the PECS system. Pronounced PEECEEs.


Never heard that one -- always heard them called "pecks".
 
User avatar
airmagnac
Posts: 404
Joined: Wed Apr 18, 2012 10:24 pm

Re: 787 Large Motor Controllers

Wed Mar 08, 2017 10:41 pm

These equipment are power electronics, their main role is to modulate the power supply to the high power electric motors depending on current operational needs and environment, and deliver the required load without wasting power.

If you wish to research on the web, and insofar as no specialized architecture is used, the main parts are called IGBTs which can be seen as On/Off switches. They take in an HVDC signal (+-270V DC) and chop it at a frequency of around several kHz. The output signal is called Pulse Width Modulated (PWM) and it's characteristics will tune the motor load.

The efficiency of these things is quite high, it can be in the 90-97% range, but with the high powers involved in such small volumes, even 5% loss as heat can require extensive cooling aids. In this case, a complex liquid cooling system with an exchanger to dump the heat out of the fuselage and into the atmosphere.

The big problem is that these things are sensitive to temperature and humidity, so the, have to be installed in the pressurized fuselage, whereas their loads are usually outside. So the overall physical footprint ends up being much more complex than with the classic bleed or hydraulic power systems.
My goal as an engineer is to fill my soul with coffee and become immortal
 
WIederling
Posts: 3089
Joined: Sun Sep 13, 2015 2:15 pm

Re: 787 Large Motor Controllers

Thu Mar 09, 2017 8:35 am

airmagnac wrote:
The efficiency of these things is quite high, it can be in the 90-97% range, but with the high powers involved in such small volumes, even 5% loss as heat can require extensive cooling aids. In this case, a complex liquid cooling system with an exchanger to dump the heat out of the fuselage and into the atmosphere.

The big problem is that these things are sensitive to temperature and humidity, so the, have to be installed in the pressurized fuselage, whereas their loads are usually outside. So the overall physical footprint ends up being much more complex than with the classic bleed or hydraulic power systems.


You enumerate some of the reasons why I think that Boeing stepped into this one or two generations too early.
Renewables and Automotive are much better drivers for power electronics at the moment.

I expect Power Electronics to gain significantly in efficiency and robustness, reliability, form factor and environmental demand.

Lots of things that Boeing is learning to cope with now will not be in demand for those next generation products.

( all the Power Conversion and Motor Drive stuff leverages the basics of industrial VFD designs.)
Murphy is an optimist
 
BravoOne
Posts: 1664
Joined: Fri Apr 12, 2013 2:27 pm

Re: 787 Large Motor Controllers

Thu Mar 09, 2017 5:07 pm

7BOEING7 wrote:
BravoOne wrote:
These are liquid cooled through the Power Electronics Cooling System, better known as the PECS system. Pronounced PEECEEs.


Never heard that one -- always heard them called "pecks".



You are correct. I was thinking of something else on the L1011. My mistake. Embarrassing as I have passed the quick and dirty FAA oral on this airplane but have touched it in a few years now. Kind hard to believe that the 787 is a Legacy airplane at Boeing these days.

Who is online

Users browsing this forum: Balerit, MarkusB, Starlionblue and 4 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos