400 cycles was invented for Airplanes. Smaller transformers.
28 cycles was invented for ships. It was never implemented. Large
transformers were ok - they were ballast. The 28 cycle was dangerous
to the human body. It entered the body on a body short.

My dad lost the marrow in one of his arms when he was bumped into a 28
hz generator. His arm went out in front to protect his fall and across
two buss bars. Two burn holes and it goes to the center. He was
working on Naval Radar and other Naval power needs.

60 cycle / Hz is skin effect. So it is far safer. Consider 28 with
left arm to right leg - burn a heart out. 60 hz stops the lungs typically.

Martin

On 1/7/2017 10:29 AM, John McCoy wrote:
Leon lcb11211@swbelldotnet wrote in news:YPydndGe9p2PjuzFnZ2dnUU7-
:

Cars used to have 6 volt systems but switched to 12 volt so that the
cables could be smaller.

Sort of. The real reason it was done was because tetra-ethyl
lead was invented.

(Tetra-ethyl lead allows higher octane gasoline. Higher octane
gasoline allows higher compression engines. Higher compression
engines require more power from the starter motor to get them
started, which requires more current from the battery. During
the 1950's compression ratios went from ~6:1 to ~9:1, which
became a problem for both the battery and the cables. Hence
the switch to 12 volt electrical systems.)

John