In article , The Other Mike
scribeth thus

OKOn Fri, 18 May 2018 19:53:46 +0100, tony sayer wrote:

In article , The Other Mike
scribeth thus
On Fri, 18 May 2018 12:16:41 +0100, Max Demian wrote:

On 17/05/2018 12:26, Bill Wright wrote:
On 17/05/2018 11:07, Dave Plowman (News) wrote:
In article ,
*** The Natural Philosopher wrote:
I don't actually understand why alternators were capable of supplying
more current though.

Because they were designed to do so.

Larger dynamos were also fitted to larger cars, etc.


Alternators spun more freely than dynamos.

I'm surprised that some pedant hasn't pointed out that all alternators
/are/ dynamos - which can be AC or DC - it's just a motor trade
convention that the word "dynamo" was kept for the original DC
generators when alternators came in.

Possibly because the pedants know that a dynamo usually has a commutator and
directly produces something resembling DC, an alternator usually has slip
rings
and produces AC that has to be rectified.

Never hear then referring to the Alternators in a power station as
Dynamo's!..

OK rectified when fitted to a vehicle.

In a power station on the end of the alternator opposite from the turbine you'll
find a DC field excitation generator / pilot exciter that does have a
commutator.

I suppose thats so it can start up by itself under shudder! Black Start
conditions;?..


The brushes on those are changed on load (as in hundreds of MW of main
alternator load and twirling round at 3000rpm)



Just stand on a carefully tested rubber mat, wear nice clean properly rated
rubber gloves and just don't get it wrong. But it's only about 600v or so and
there are quite a few brushes in parallel

But if you think that's dodgy they fill the stator with water and circulate
hydrogen in the gap between the stator and rotor to keep it cool.

Why Hydrogen?...

The hydrogen being sealed on the interface between the rotating shaft and the
outside world by pressurised oil. Get a rubbing seal and it might ignite the
hydrogen make a big bang and the oil fire will burn a very big hole in the roof.


--
Tony Sayer