[TR] amps

Randall TR3driver at ca.rr.com
Wed Oct 30 15:53:51 MDT 2013

> On another subject line regarding amps in a '59 TR3A.  When I 
> first start up my TR3A and rev the engine, my amp needle will 
> move to the far right in sync with my revving the engine.  
> Once the engine warms up, this does not occur.  Any ideas 
> what would be causing this?  

When the starter cranks the engine, it draws a lot of power from the battery.  Literally hundreds of amps times however long it
takes to start the engine.  Takes a lot more to start a cold engine than a warm one; plus the battery tends to self-discharge over
time.  The control box is deliberately somewhat sensitive to temperature, and when cold will allow the generator output to
temporarily exceed the rated 19 amps (or 22 IIRC if you have the later generator & control box setup).

So, that's normal operation, as long as the current doesn't stay higher then the generator rating for more than about a minute or so
(depending on how cold it is).  If it stays up too long, your control box may be misadjusted or defective or wired wrong.

Without the action of the control box, the generator output depends almost directly on rpm.  At 1000-1200 rpm (for the generator),
it only puts out about enough to run it's own field windings and nothing for the battery.  You may even see the red light glowing,
to indicate that the cutout has opened and disconnected the generator from the battery, to prevent current flowing backwards through
the generator.  At around 2000 rpm (+- 100 rpm, again for the generator), it should be able to just barely meet it's rated capacity,
19 amps at 13.5 volts (plus the 2 amps or so it takes to run the field winding).  At higher speeds, it relies on the control box to
limit the output, as otherwise the generator will easily generate enough current to burn itself up.

As John Herrera used to say, I have experimented with this :)


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