270VDC AIRCRAFT CIRCUIT WIRING

[faresos]

Hello Everyone,

Can we use THHN/THWN-2 wires for 270VDC circuit (used to power an outlet for aircraft power plug)? Is there anything I need to be concern of as far sizing this circuits (100A), other than voltage drop? Thanks,

 

[Geber]

I saw an FAA-recommended training video which warned against using solid wire on aircraft. The video claimed solid wire tended to break of at connections because of vibration.

 

[faresos]

I saw an FAA-recommended training video which warned against using solid wire on aircraft. The video claimed solid wire tended to break of at connections because of vibration.

it will be stranded type (for 100A circuit)

 

[tortuga]

Is this wiring in the plane itself? Or wiring in say a maintenance hanger to supply power to an aircraft?

 

[petersonra]

All the 270 vdc load banks I designed over the years used stranded wire. Mostly mtw with an occasional bit of thhn.

 

[winnie]

it will be stranded type (for 100A circuit)

IMHO if you are making connections subject to vibration, then you want to be sure you account for that.

See https://www.iewc.com/resources/technical-guide/stranding-classes for the different sort of stranding available.

Normal THHN would be class B. My guess is you want class D or G for aviation use, but that is a guess.

-Jon

 

[tom baker]

This is premise wiring for a receptacle in a hanger? Then you would follow the rules for wiring in Chapter 3. Note: some hangers can be a classified location per chapter 5

 

[faresos]

Is this wiring in the plane itself? Or wiring in say a maintenance hanger to supply power to an aircraft?

it's for maintenance hangar to supply power to an aircraft. The wiring I'm referring to is from the panelboard to the outlets.

 

[winnie]

Oh. Ordinary THHN should be good to go.

 

[drcampbell]

I saw an FAA-recommended training video which warned against using solid wire on aircraft. The video claimed solid wire tended to break of at connections because of vibration.

Even 7-strand wire isn't really suitable for vehicles.

Do you know what types of aircraft use 270 VDC, and what they use it for?

 

[junkhound]

Even 7-strand wire isn't really suitable for vehicles.

Do you know what types of aircraft use 270 VDC, and what they use it for?

F-22 and 787 and others use 270 Vdc. BAC13-70 wire typical, or 13-78

 

[synchro]

F-22 and 787 and others use 270 Vdc. BAC13-70 wire typical, or 13-78

And according to the article at the link below, on the 787 +-270VDC buses supply substantial loads from VFDs:

"The ±270 VDC system supports a handful of large-rated adjustable speed motors required for the no-bleed architecture. These include cabin pressurization compressor motors, ram air fan motors, the nitrogen-generation-system compressor used for fuel-tank inerting, and large hydraulic pump motors."

The primary power is generated at 235 VAC 380-800Hz, and from which 115 VAC, +-270VDC, and 28 VDC are derived and distributed.

http://www.boeing.ch/commercial/aeromagazine/articles/qtr_4_07/article_02_3.html

 

[LarryFine]

That's how I would have done it.

 

[junkhound]

235 VAC 380-800Hz

Many vendors sent existing 400 Hz designs for use on the test flight aircraft.

More than a few forgot to analyze for the 380-800 Hz part. The 19 pulse ATRUS used to generate the 270 Vdc produce a lot of 17th and 19th harmonics, those would hit the resonance of the EMI filters as engine speed changed and blowup power supply capacitors.

 

[Tip DS]

I generally stick with wiring types listed in AS50881.