<VV> Alternator question

[JVHRoberts at aol.com]

No transformer, just a direct output from the alternator, and it was DC,  
meaning only devices like light bulbs, heaters, and brush type universal motors,  
like drills and saws could be used. But they did punch out about 3000 watts! 
 
Yeah, I remember the Electroclear windshields. A thin layer of indium tin  
oxide with about 90-120 volts going through it, because the resistance was too  
high to get useful power at 12v. Neat idea. I wonder how much those 
alternators  go for? 
 
Anyhow, there are too many electronics on today's cars to survive a spike.  
However, there's a standard out there that anything electronic on a car be able 
 to survive a spike of 80 volts for something like half a second. I am sure  
someone has more info on this. 
Furthermore, a truly modern alternator has different diodes in it. They are  
avalanche diodes which essentially conduct backwards STRONGLY if they are  
reverse biased by more than 30 volts or so, again, in an effort to protect  
everything from a sudden disconnect of the battery. These alternators could be  run 
unloaded, but I am not sure how the regulator inside would like it....
 
In a message dated 4/11/2006 11:13:43 P.M. Eastern Standard Time,  
corvairduval at cox.net writes:

I  remember seeing the little boxes to mount under the hood with a 120 volt 
AC  outlet on them. I just thought there was a step up transformer to change 12 
 VAC before the diodes to 120VAC at about 100 watts (100VA). 

Now, there  is also the 120 Volt alternators on Thunderbirds to power the 
electrically  heated windshield defroster! Late 70's, you would find two 
alternators under  the hood that looked similar, just one said HIGH VOLTAGE on a 
label! This  defroster was not lines like a rear window defroster, but something 
metalic in  the plastic inner layer that would heat up but not obstruct vision 
like the  wires.

Yes, the battery is a serious current sink. If you remove the  battery, the 
voltage does go up, enough that it is no longer recomended to  remove a battery 
cable on a running engine to see if the engine still runs,  and therefore the 
alternator is OK. Much too sensitive electronics now on  board for that.

Frank DuVal

_JVHRoberts at aol.com_ (mailto:JVHRoberts at aol.com)  wrote:  
 
I agree, connecting to a battery is the safest thing. But alternators  are 
funny things. I hear ya on the turns ratio thing, but remember WAY back,  when 
there were conversions to get 120 volts DC out of a standard  alternator? The 
rotor didn't have anything special done to it, it's just  that alternators are 
usually connected to SERIOUS current sinks. Remove the  sink, and the voltage 
goes way up. 
But, like you said, a bit of research goes a long way.