P plate training ...not

Aren't options one and two the same?...

 

Plonk

 

It was benign to begin with as per the "special magic hat". Then when it
wasn't a "my dad take me to (insert Merkin restaurant), he's better than
yours..."

That is a different spin. Cheers

H

 

So, you think I was trying to elicit guilt? Am I missing something? I
don't follow the logic.

Hammo

 

I'll assume you were actually meaning to reply to Clem there.

 

I don't follow the logic and this should have been kept offline. I find the
insinuations despicable.

Hammo

 

Well I'm not feeling PARTICULARLY tantalised but without a circuit there is
no current (only potential).
No current in the stator means that there's no electromagnetism so nothing
is opposing the spinning of your fixed magnets.
Allow current to flow by providing a circuit (from the negatively-charged
side of the stator-coil to the positive side) and there can be
electromagnetism and thus repulsion. The "shorter" the circuit (i.e
brighter bulb) and the more the current and the more the resistance.
The problem is that the voltage is, as you point out, still dependent on the
revolutions so you're still gonna' have a dim headlight if you're pedalling
slowly.
Enter the electromagnetic rotor and the regulator which sends a certain
amount of voltage to the rotor-coil (it's a fixed resistance so the only way
you can vary the current is by varying the voltage).
Now if you want a brighter headlight at low revolutions you whack a big
voltage onto the rotor, hey presto; more magnetism and more current in the
stator and in the headlight but heaps harder to pedal (because the output
energy is still coming from your legs; you're just changing the "gearing")
The flip side is that the regulator can back it right off when you're
spinning at high revolutions so you don't blow your bulb.

The MCG situation is like fitting the brightest bulb you can find (or
virtually a short circuit).
Now the alternator current in the stator is at it's absolute maximum and
magnetic repulsion at it's strongest so it hardest to turn.
Whether or not it can actually light the lights though depends on the
resistance of the circuit (and the thickness of the wires)... as well as
your aforementioned revolutions.
A 55W 12V headlight has a 2.6 ohm filament (it actually changes as it heats
up but that's not important at this stage) so an alternator needs to feed it
4.6 amps to light it.
The stator coils themselves have some internal resistance (say .26 ohm) so
the alternator has to generate 13.2V (or more) because at 4.6 amps it's
unavoidably wasting 1.2V on ITSELF (Total circuit resistance is 2.6 + .26
ohms so the 13.2 gets shared 2.6/.26ohm = 12/1.2V)

No big deal so far; but plug in the MCG and your "headlight" resistance
drops to .01 ohm. (or whatever would be required to run 20,000Watts of
theoretical lights a theoretical 12V super alternator).
Now your total circuit resistance is .27 ohms, the circuit current is
52.8amps and the 13.2V gets carved up 2.6/.01 = 12.7/.5.
Now you're only supplying half a volt to the MCG (at 53amps) so your lights
are only 1/24th as bright as they're supposed to be and the other 12.7 volts
(at 53amps) is creating heat and magnetic-repulsion in your alternator.

You're doing a hell of a lot of work but you're not really achieving
anything. (Much like I'm doing with this post!)

 

Yep I understand that. It's just that you replied to my post and comment, and as far as I can see I'm not insinuating anything of
the kind. I don't feel guilty and I don't feel I was being led to feel so.

 

"And you're being hurtful when I was only trying to help....."

 

Naah; just drinking plonk wouldn't explain it!

 

Hmmm... You've got a point

 

Not at all, Professor, you're doing fine. TFTH.

 

Or maybe you know me. ;-)

 

The _voltage_ is determined by the rate the magnets are spinning at.
The _current_ is what causes the torque effect.
The _power_ is voltage * current. When you're drawing no power, no
current is flowing, so there's no back-torque.

-----sharks

 

But this NG is full of people that torque back.

 

No, you don't. You prefer to go off at tangents.

Theo

 

Sounds like you're trying to elicit guilt Hamish.

Theo

 

Arrgh gawd I'm gonna' look like a total sychophant here but;

[hearty applause]

Pure gold!

 

I'm on the INside.

 

As usual, I'm 'standing on the outside, looking in'.
---
Cheers

PeterC [aka MildThing]


'01 Yamaha FJR1300

www.dmcsc.org.au
http://eladesom.com.au/ulysses/
# 37181