Frequency preference BS7671

[lyledunn]

Can anyone suggest why BS7671 2001 states a preference for 50, 60 and 400hz? I can understand the first two but where does the 400hz come from?

 

[peterb]

400 Hz is standard for aircraft electrical systems. The higher frequency results in physically smaller and hence lighter equipment (less iron required)

 

[nbucska]

Peterb : Less filtering,-- smaller caps, inductors, -- too. <nbucska@pcperipherals.com>

 

[peterb]

nbucska -
Of course you're right that filter components will also be smaller, but I'm not too sure that there are that many filters or power factor correction capacitors installed on an aircraft power distribution system. The bulky/heavy equipment will tend to be the generators and any AC motors, where the saving in weight due to less iron will be most noticeable.
Perhaps someone else has some specifics on this?

 

[lyledunn]

Thanks guys. Electrical equipment on aircraft is specifically excluded from the scope of BS7671 but I was very interested in the use of such a frequency. Perhaps someone knows of a common use of 400Hz for electrical installations of some type within buildings.

 

[ongchazira]

We have PMGs of our alternators, that generate the energy required for the excitation of the main field, rated at 400hz. Here it is probably used for smooth DC field current.

 

[cemike]

Any facility in which maintenance or calibration is done on 400 Hz aircraft equipment will have a requirement for 400 Hz power within the facility.

 

[aircraftengr]

So can it be concluded that the 400Hz frequency is basically to allow smaller and lighter equipment in the aircraft? There didn't seem to be a conclusive answer. Actually, I study aeronautical engineering, but the electrical parts are a little off my scope.

 

[cuky2000]

400 Hz is also use in submarine and other military applications.

Still today there are 25 Hz system in operation for RR application. 120Hz & 150 Hz were used in the eraly development of electricity.

See the enclose site for additional info:

http://www.ieee.org/organizations/history_center/historical_faqs.html#60 cycles

http://www.achrnews.com/CDA/ArticleInformation/features/BNP__Features__Item/0,1338,64996,00.html

 

[jbartos]

Suggestion: Visit

http://www.atd.siemens.de/airports/download/Macau.pdf

for airport building providing a ground 400Hz power supply to aircrafts on the ground.
In some cases, the following equipment may require 400Hz from the building:
1. Cranes
2. Computers
3. Transmitters
4. Communication equipment
5. Etc.

 

[trainman10]

We have been asking this question ourselves. Smaller components may work for modern aircraft but 400 Hz power was in use back in the days when military UHF radios were 80+pounds (ARC-27). Most of them used 28 VDC input power with an internal M/G to convert it to 400 HZ, 115VAC. 28 VDC was used on most early aircraft as it did not require any speed regulation as an A/C generator needs. None of us can come up with a good reason as to why 400 Hz was picked. Why not 500 or 600 Hz?