[modeleng] Re: Topsy - to charge and how to charge, that is the question!

  • From: Peter Sheppard <peter.sheppard@xxxxxxxxxx>
  • To: "'modeleng@xxxxxxxxxxxxx'" <modeleng@xxxxxxxxxxxxx>
  • Date: Wed, 30 Mar 2005 09:51:23 +0100

All,

Next phase.

Last night I finally got the electrics in state that I could try it.

Apart from the petrol engine not running properly (it ticks over OK but seems 
to suffer from fuel starvation at higher revs - it runs for a while then dies!)

With the alternator field "off" the voltage was around 26.2 volts (one battery 
was in use on an electric locomotive over the weekend, so the volts may be down 
slightly).  With the engine running and the field on (apart from slowing the 
petrol engine quite markedly - and this was with no load on the battery!) the 
battery volts rose to around 28v.

So, it looks like the alternator works.

So my question remains, what is better, weaken the field (which is intrusive to 
the alternator) and leave the engine running all the time, or leave the field 
as is and switch the charge to a dummy load whenever power is taken by the 
motor?  I am still concerned by regenerative braking taking the volts up to 36 
and damaging the alternator.

I suspect it will depend on how much time the locomotive is running (i.e. 
hauling, not charging), versus sitting there idling (and thus charging).

Cheers

Peter


On Tuesday, March 29, 2005 10:43 AM, Peter Sheppard 
[SMTP:peter.sheppard@xxxxxxxxxx] wrote:
>
> Topsy is a hybrid loco.
>
> He/she has the main drive from a large fork lift motor which has its 
batteries
>
> topped up from a 24v alternator driven off a small petrol engine.
>


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