Dave Liquorice wrote:
On 09 Jun 2008 09:55:39 GMT, Andrew Gabriel wrote:

and still more efficient even allowing for a motor-generator set to
create the 400Hz supply.

Er, I've never heard of an alternator that can produce a squarewave
output... Surely the physical nature of the beast (coils and magnetic
fields) means that the waveform is sine (or close to it).

Isn't the improved efficiency down to the higher frequency thus less
discharge of the reservoirs for a given load current?

I dont know the alternators or psus in question, I just wondered if
the cost & efficiency gain was down to smaller transformers
running at 400Hz, and of course smaller reservoir caps. 400Hz TFs
have much lower resistance windings for the same throughput.

Alternators dont produce square output of course, but they can
produce non-sine by using a commutator, fwiw. In principle this
could remove the need for a rectifier, but what actually was done
I dont know.


NT