Generator basics:

[J D]

Very informative post Nutty.

As per always.

Love reading your posts most are informative the balance are just plain funny.




I'll try & arc something out on the bike so I can ask how to fix it.

[ian9toes]

Originally Posted by Kero

The insulated one is the igniter (pulser coil), it provides power to the coil to create spark.

I once rewound the (whatever) on my old 350 so that the headlight was brighter than a candle.

XR 350 that is.
A bike that I was once told didn't exist.

The pole with less windings on it Ian is like that because, as Nutty stated in the first part of his post, voltage= strength of magnetic field x number of windings x rpm

Thanks kero, that makes sense. But you would think it wouldn't be too hard to evenly spread out the required number of windings and have them all the same.

Perhaps they do a few tests while winding the last one and adjust it's number of windings to get the desired actual voltage, and not just a theoretical value?

[2banga]

Originally Posted by Nutty

There's usually only two output wires from bike alternators, generally yellow and white, these two connections are both AC. These wires are usually accompanied in their connector by two wires from the pulser coil (crank angle sensor)

So in the bikes its not a 3 phase current that is rectified to provide an almost true DC?

[jd_crf]

Originally Posted by 2banga

So in the bikes its not a 3 phase current that is rectified to provide an almost true DC?

It is on a DRZ (3 yellow wires, around 65V from memory), and could be on other bikes.

[Nutty]

Originally Posted by burner

what limits rotational speed on a series DC motor ?

Mechanical load, windage (aerodynamic) losses and frictional losses.

They design small ones with inbuilt aero drag so they don't overspeed and blow up, I've seen a 415V, 5kW let go though, spectacular.

Originally Posted by burner

is there a limit ?

No, not electrical, only as above.

Originally Posted by burner

what does the capacitor in an AC (capacitor start) motor do, and how does it do this, and what vector leads ?

The cap in a cap start motor makes the current in the start winding occur before the current in the run winding, it is this time delay that creates torque. If the cap wasn't there the AC motor would run if kick started but wouldn't self-start. The vector arrangement doesn't affect anything other than direction of rotation.

Originally Posted by ian9toes

"Finally, no-one gets a 'stator' rewound! The two electrical parts down there are an armature winding and a pulser coil..."

If the stator was the permanent magnets as I enquired, this would satisfy that statement.

But I just had a look inside and the part that doesn't move (the stator) is in fact the armature. As far as I'm concerned the armature and stator in my alternator are one and the same. Therefore it makes sense to 'get the stator rewound'.

It might to a layman, but the definitions I posted are clear as a bell and your 'sense' isn't going to change 150 years of electrical terminology. If you are doing an electrical repair it is to the armature. If you are doing a mechanical repair it is to the stator.

Originally Posted by ian9toes

I have another question. Why does that one coil indicated by the screwdriver have way less windings than all the others?

The alternator shuts down slightly as it passes the pulser coil, the next generation coil is only 1/2 wound to ramp-up the voltage generation in a less aggressive manner, it's nicer on the rec/reg.

Originally Posted by ian9toes

And why is the one next to it insulated like that, and not the others?

It's the pulser coil a.k.a. ignitor (old school term)

Originally Posted by 2banga

So in the bikes its not a 3 phase current that is rectified to provide an almost true DC?

Not needed 2B, a two-pole, single-phase bike alternator is making AC at 200Hz at 12,000 r.p.m. That's way higher frequency than most 3 phase systems run at.

Some low-revving bigger 4Ts run three phase, old XRs etc, not needed on a race bike

[Chewy]

Bikes that need a decent lighting and charging system are generally 3 phase. Some dirtbikes are only single phase.

[ian9toes]

Thanks Nutty, but you missed a previous question.

If I perform that test with the paper clips, will an armature on the way out give a noticeable drop in the voltage before it actually fails and leaves me stranded?

Is it something you check very often?

[Nutty]

Originally Posted by ian9toes

Thanks Nutty, but you missed a previous question. My apologies Ian.

If I perform that test with the paper clips, will an armature on the way out give a noticeable drop in the voltage before it actually fails and leaves me stranded? No, usually not.

Is it something you check very often?

No mate, on a need only basis. You get way more problems with pulser coils failing though, especially RFS Katos and CR500s.

Originally Posted by Chewy

Bikes that need a decent lighting and charging system are generally 3 phase. Some dirtbikes are only single phase.

Other way round my friend, all WRs are single phase, all EXC Katos, all Shercos, All Betas, etc. TMs are optional single/two phase. Very few dirt bikes under 500cc run three phase alternators.

[ian9toes]

Taken from an engineering website

Stator Frame and Rotor Construction

The stator frame is used to hold the armature windings in alternators, and in case of larger diameter alternators (which are slow speed) the stator frame is cast out of sections and there are holes for ventilation in the casting itself. The recent trends towards such stator construction are more in favour of using mild steel plates which are welded together rather than using castings.

It seems nearly everyone uses the layman term of stator to refer to both the armature windings and the stator. But is not the correct term

Not that I doubted you at all Nutty




So in order to avoid being left stranded with a failed alternator, should I get it rewound periodically?

It's something that concerns me because it's happened once before and I ride alone a lot.

[Nutty]

Originally Posted by ian9toes

It seems nearly everyone uses the layman term of stator to refer to both the armature windings and the stator. But is not the correct term. Not that I doubted you at all Nutty

You need to read your own quote mate...

Taken from an engineering website:

The stator frame is used to hold the armature windings in alternators,

If the the armature windings are held in place BY the stator frame (and they are), then the armature windings and the stator frame MUST be two separate parts (and they are).

You just kicked yourself in the arse. I'm doing the right thing trying to give everyone a bit of electrical insight and I get a non-trained person trying to cloud the waters. I was hoping this forum could be the one place on DBW exempt from narky vacuous fluff but I guess it's endemic..c'est la vie.

p.s. 40 years in the trade mate...