[Amps] *** SPAM *** Re: Hotswitching

[R at contesting.com]

On Apr 8, 2006, at 11:51 PM, Peter Chadwick wrote:

> Rich said:
>
> >Motor vehicles are beginning to go to higher battery potentials to 
> save on Cu expense and
> on vehicle weight,<
>
> Do you remember 6 volt electrical systems in cars?

I owned a 1963 VW bus that was 6v.  Going mobile was an ordeal.
A few years thereafter, when VW realized that they needed to up the 
voltage, a number of their engineers argued for 24v, but management 
knew better and went for 12v.
>
> Kilovac at one time in their publicity had a whole load of stuff about 
> the vacuum conactors

Contactor -- a largish relay

> used to switch th 270 volt DC bus used on the F22. The elctrical 
> requirements there must be pretty big - sobering thought, at the 
> outbreak of WW2, the standard power source for RAF medium and heavy 
> bombers was an engine driven generator giving 500 watts at 24 volts. 
> They soon found this inadequate.

The amount of Cu wasted wiring 24v airplanes during WW-2 is impressive. 
  At one point, Cu was in such short supply that GE started using #14 
silver to build the 25uH roller coil used in the BC-375 transmitter.
>
> Diodes speed for protecting the VMOS - I don't know. 1N4008 wouldn't 
> do it, 1N4148 was fast enough but couldn't handle much power. I 
> suspect some of the fast diodes around these days would do.

thanx, Peter, and Dv/Dt could be slowed down with a suitable C.
>
>
> 73
>
> Peter G3RZP



Rich Measures, 805.386.3734, AG6K, www.somis.org