+/- 270V (540V) supply as opposed to a 0 - 270V supply

[sp3761]

Need Help...PLease..

We are currently having discussions about the relative merrits of various powers supplies and would like to canvas your opinion on the risks (if any) of using a +/- 270V (540V) supply as opposed to a 0 - 270V supply for the aircraft.

Please provide your opinion from experience and expertize. Input is highly appreciated.

 

[jcai]

GOOD MORNING FOLKS - DON'T KNOW WHAT YOU MEAN BY + - 270V. = 540V. ? .
ALL 270 V. AIRCRAFT ARE SIMPLY 270 V. D.C. - THIS IS ONLY USED ON SOME U.S.A.F. AIRPLANES - F-22 ETC + SPACE PLATFORMS - WHAT AIRCRAFT ARE YOU REFERRING TO ? - ALL OTHER AIRCRAFT USE 208V / 115V. - 400HZ - OR SMALLER ONES USE 28.5 V. D.C. SYSTEMS - SOME OLD BRIT AIRPLANES LIKE BRITTANIA / COMET DID USE 28 /112 V.D.C. - AND OLDER RUSSIAN MILITARY AIRPLANES LIKE MIG 19 - USED 28/56 V. D.C. BEST REGARDS J.C.

 

[BrianR]

I am not sure why you would want to use +/- 270VDC compared to +270V. What advantage would you get?

The purpose of using 270VDC is that it is easily obtained by rectifying a standard 3 phase alternator and it does not require speed regulation to maintain 400Hz. The cabling is lighter and light weight static inverter power supplies are used at the load.

There is a corona issue too. Bare conductors will start to corona at around 250VRMS (350VDC) at altitudes in excess of 20,000ft. I know +/- 270V is still only |270V| but adjacent terminals could have 540V. I repeat, why?

 

[sp3761]

Thanks for the brief answer to jcai and BrianR.

We are currently working on R&T and Boeing & A-UK both wants to see the future of aircraft operation and weight if 270 +/- VDC mean 540V DC across without ground is used for more electric aircraft on high power requirements. Indirectly seems cable weight is the issue.

Please guide further if any one can.

 

[IRstuff]

Avionics cable weight is rarely dictated by amperage. The shielding, insulation and connectors are usually more weighty than the actual conductor.

TTFN

 

[BrianR]

An isolated ground system is an extension of the 2 or 4-wire power systems we have used on some military aircraft to eliminate airframe currents. It sounds like a good idea but there will still be capacitively induced transient and ripple related ground currents so insulation from ground remains an issue.

The voltage rating of aircraft cable such as M22659/32 is commonly 600V so this would not be sufficient for a 540V installation. I know the trend in wire insulation is to reintroduce the dreaded kapton enclosed in inner and outer sleeves of PTFE so you get effective insulation at light weight. There will certainly be a weight reduction gained by using a +/-270V system.

 

[american500]

hello,

Are you guys going to implement high voltage dc current on civil aircrafts or is this being developed for military programs?

Thank you
jishi

 

[sp3761]

Implementation could be both Civil and MIL. It all depends on trade study particularly on weight saving.

More thought and answers needed. Please help

SP3761