On Nov 5, 6:48*am, George wrote:
On 5 Nov, 00:41, Grimly Curmudgeon
wrote:



We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember George
saying something like:

Having read all these posts I am very motivated now. However this is a
big machine and I was planning to build it all on two heavy bits of
channel and make up the drive coupling to one of two Perkins P3
engines I have - or even sacrifice the 1.9 litre engine out of an old
Mondeo I am still using, but which has a limited expected life. *This
is pretty efficient and most of all, - quiet, at this sort of speed.

What's the rated speed of the alternator?

3000rpm - you're laughing for direct drive.

If it's 1500rpm, you'll find a car engine with a road camshaft to be
right on the edge of its torque curve if you pull any real power out of
that set at low speeds if it's direct coupled.
I'd look at an HD pulley drive to bring the engine speed up to ~2000rpm
if possible.

If the speed is 750 rpm, forget direct coupling entirely.

Thanks for that. *It is 1500. rpm. *But I am only going to try and use
this 65 Kva alternator because I have it. *The only other one I have
is about 5Kva and not strong enough to drive the 3 main motors I have
in my workshop, currently a Herbert Lathe *5 or 7 1/2 HP . A Denbigh
Mill and a low HP pillar drill. *I am also thinking of a big welding,
- plasma cutter set. Second hand 3 phase is cheaper as not so many
people have it.

My worst load is the Herbert and I am still able to get it up to speed
if I wait a bit, on a cold morning, using a 3HP. *1 to 3 phase
converter. * *The sheer weight of the alternator rotating parts will
give a nice start-up capability. *I am not all that concerned about
exact frequency stability. *A pretty simple AVR will also suffice. *In
the future I may use it to charge up inverter batteries for a combined
heat and power set up, running on bio-diesel. *It will be neater to
directly couple it so I would prefer to run at 1500. *It will go in an
insulated space and so not annoy neighbours, the water being plumbed
in to a hot water tank and central heating. *Waste not, want not. I
shall only start it up when I need it.

What do you think?

Regards George.

There sholdnt be anything preventing you from getting it rnning, as
long as it works. With 3 machine shop tools on a 65kva gen you wont
need regulation, so even if the reg & exciter were toasted you could
run the main machine's field off an unregged supply such as a car
alternator (with its regulation removed).


NT