Generators - info required

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Member for

19 years 1 month

Posts: 8

Why is the industry looking to move from 115VAC 400Hz constant frequency to 115 VAc 200 Hz and 230 VAC 400 Hz variable frequency generators?

I don't get it. Is there some sort of cost/weight saving here? And surely having a variable frequency will effect frequency dependant components such as actuators??

Can anyone shed any light?

Original post

Member for

24 years 2 months

Posts: 4,887

A Hertz is an indication of power. The more hertz, the more power per second is transferred. Therefor, the higher the Hz ratio the more power can be transported per second.

This also means that the current electricity grids get more efficient. Instead of installing a new series electricity cables everywhere (as well as their back-ups) they can use the current cables thereby saving weight.

This technology is hard to retrofit though. The added power may be too much for the cables to handle. You could compare it with a waterline. If you suddenly double the pressure, it may break. So don't expect older planes to get this system. The newer planes will be though, and some of the newer models now on the market (think 737NG, 777, A320, A330) MAY be equiped with the stronger cables required. Maybe someone else can confirm/deny this suspision?

In the past the planes used relatively little electricity. The cockpit, cabin lighting and shared TV(s) and in case of Airbus FBW. Nowadays though much more electricity is required for more cockpit instruments and much much more IFE. Nowadays most new (longhaul) planes are delivered with one TV per seat. That eats power at astonishing rates.

Member for

19 years 8 months

Posts: 500

My guess is that this is to save the weight of the constant speed units required to maintain 400hz.
I assume that modern solid state electronics can be used to provide a stable frequency when required & save weight.

Member for

19 years 1 month

Posts: 8

Thanks Guys