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

  • From: "R.L. Roebuck" <rlr20@xxxxxxxxxxxxx>
  • To: "'modeleng@xxxxxxxxxxxxx'" <modeleng@xxxxxxxxxxxxx>
  • Date: Wed, 30 Mar 2005 12:13:20 +0100 (BST)

...also, do you have any details from the makers/ratings plate on the
alternator?

Yours,


Rich.

On Wed, 30 Mar 2005, R.L. Roebuck wrote:

> Hi there Peter,
>
> Can I ask - how are you acheiving motor control in all of this. Do you
> have a PWM unit lined up such as 4QD supply, or are you thinking of using
> a large resistance, or something else?
>
> Yours,
>
>
> Rich.
>
>
> On Wed, 30 Mar 2005, Peter Sheppard wrote:
>
> > John,
> >
> > Thanks for that.
> >
> > I note the use of the diode, but shouldn't it be the +ive terminal to the
> > battery ? (the pointy end!)
> >
> > With regard to the petrol/electric bit, my main concern is that when the 
> > motor
> > is pulling serious current (it limits at 96A on 24v dc) then the alternator
> > will try and fill that gap (or at least it will try until it current 
> > limits).
> >
> > I only have a 3/4 hp petrol engine driving the alternator, so I have visions
> > that it may stall.  The only thing I suppose is to try it.  I have no idea 
> > what
> > the maximum charge current of a 24v alternator is - any suggestions?
> >
> > Cheers
> >
> > Peter
> >
> >
> >
> >
> >
> > <snip>
> > > To prevent any external voltage source damaging the alternator such as
> > > regenerative braking you need a heavy current diode in the main alternator
> > > output connected so that its normal output current is conducted but any
> > > reverse current is inhibited. Just connect the diode +ve terminal to the
> > > alternator and the negative terminal to the load.
> > <snip>
> > > This would be a standard sort of setup and will solve any problems of
> > > overcharging and reverse current through the alternator. The charge will
> > > also automatically increase to take up the load of the motor.
> > >
> > > John Rippengal.
> > >
> > > From: "Peter Sheppard" <peter.sheppard@xxxxxxxxxx>
> > >
> > >
> > > > 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
> > >
> > > MODEL ENGINEERING DISCUSSION LIST.
> > >
> > > To UNSUBSCRIBE from this list, send a blank email to,
> > > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject
> > > line.
> >
> > MODEL ENGINEERING DISCUSSION LIST.
> >
> > To UNSUBSCRIBE from this list, send a blank email to,
> > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject 
> > line.
> >
> >
>
>

MODEL ENGINEERING DISCUSSION LIST.

To UNSUBSCRIBE from this list, send a blank email to, 
modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.

Other related posts:

  1. Home
  2. modeleng
  3. Archive
  4. 03-2005