[AMPS] arcs

[Rich Measures]

>Rich says
>
>>I am not certain, although I have a suspicion that arcing ability
>>increases with frequency. .......  I have seen some incredulous arcs in
>>my 432MHz 4cx250R amplifier.  I have seen some incredulous tune-C arcs
>in
>>my SB-220 at 110MHz.
>
>Rich, do you think it possible that the increase in voltage at LF is due
>to the fact that at low frequencies, the arc gets the chance to
>extinguish during the zero crossing, while at HF, the plasma takes so
>long to disperse (in terms of the period of 1 cycle) that it stays a
>conductor? 
I don't know.
...snip...

>......... The
>arcs you can get with DC leads me to wonder why the power bus for modern
>US military aircraft is 270volts dc, needing vacuum contactors to
>control it. In my innocence, I'd have thought a 400Hz generator and AC
>system would be lighter.

115v/400Hz tends to cause interference problems inside an aircraft.  270V 
DC is better because it saves (copper) weight and is virtually 
interference free---even though interrupting it is somewhat trickier.  
Transient V suppressors are especially useful across  DC switch contacts. 
 
-  Auto manufacturers could reduce production costs if they switched from 
12v to a higher voltage.   
-  For an electric car, 270V makes sense.  
-  This computer will run on 140V DC to 340V DC or 100V AC to 250V AC.  
However, to use it on DC, a transient V suppressor would be needed across 
the on/off contacts.  
Rich---

R. L. Measures, 805-386-3734, AG6K   


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