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Re: TR4A voltage regulator problem - follow-up

To: triumphs@autox.team.net (Triumphs List), tr3driver@comcast.net
Subject: Re: TR4A voltage regulator problem - follow-up
From: spamiam@comcast.net
Date: Tue, 09 Aug 2005 12:36:14 +0000
Thanks for the feedback.  I agree that it would be wisest to keep to the 22 amp 
limit despite the possibility of wringing a couple more amps.

Of course I am making the current draw judgements based on my car's ammeter 
whose reading is approximate at best.  Still, I think that full scale charging 
PLUS lights is over 22 amps no matter what!

I am going to get that semiconductor-based regulator and test it out.  Since it 
is completely contained within the original control box and uses the same 
terminals, it will be totall invisible.

I wonder how/why my regulator comes to so significantly exceed the current 
specifications.  I suppose the same number of turns of the wire using a 
slightly larger diameter will allow more current for the same magnetic field.  
Or, maybe I simply have the wrong regulator and it is designed for more 
current....  

The other issue is that unless I had a depleted battery, and was away from an 
AC charger, it would not matter what the regulator woud do because I would 
never draw more than 22 amps anyway.  

Well, I will get something that is tested to give the correct voltage AND 
current limits!

-Tony

-------------- Original message -------------- 

> > So, What is really the maximum continuous current rating for our 
> > generators? I would assume that 22 amps is the limit based on what I saw 
> > in the specifications page of the Haynes manual. But my present regulator 
> > is allowing more than that! I am going to order one of these electronic 
> > regulators and I want to specify the highest safe current limit. So, what 
> > should I tell him? 
> 
> I honestly don't know the answer to that, Tony. Personally, I'd be leery of 
> exceeding the 22 amp (19 for earlier units on TR2/3) rating for very long; 
>since 
> I know from personal experience that it's not hard to burn up a TR generator 
>in 
> 30 or 40 minutes of continued high-speed overcurrent operation. 
> 
> I believe the original circuit worked as well as it did because the old 
> batteries' charge voltage would rise fairly quickly to at least 13v or so, in 
> less time than it took for the generator to overheat and start throwing 
>solder. 
> And sometimes, of course, it simply let the generator burn up. I've never 
> understood the decision to use the 2-coil regulator on the TRs, especially 
>since 
> a 3-coil unit was used on Spitfire (and Vitesse). 
> 
> Unless you're willing to test several units to destruction, my suggestion 
>would 
> be to give him the factory rating and consider yourself lucky that your 'hot' 
> regulator didn't burn up the generator. I suppose the ultimate setup would be 
> to measure the internal temperature of the generator (and limit it), perhaps 
>by 
> measuring the field coil resistance ... but it hardly seems worth the effort 
>to 
> me... 
> 
> Randall 




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