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How is the power generator circuit protected??

P

pswiatki

Tuned and Synch'ed
Joined
Aug 26, 2011
Messages
96
Location
Wrocław, POLSKA
I am redoing 2008 Breva 1200 wiring diagram (cable colours, part description strings, multi-layer, etc.) in SVG format. Not that I have too much free time, but I want to know exactly what happened to my bike when it burned wires near the headlight and the ignition lock.
If my understanding of what I see is correct it seems that (unless the generator has some internal fuse or another type of overcurrent protection) there is no current limits other than the generator's ability to serve it. The only fuse I can see is at the battery terminal (30A), but that can only protect the battery from excessive charging current when the engine is running, or from draining when the engine is stopped. Is this correct?
If so, it would nicely explain burnt wires here and there (they gave up faster than the 550W generator's coils).

By the way: anyone knows of any other attempts at improving the original version of the Breva wiring diagram?
I'd rather avoid duplicating effort if it has already been done.
 
You have a few misunderstandings of what's going on with the electricity on your bike. The alternator (you call a generator) has
a voltage regulator that is responsible for the alternator output . They (generally) aren't fused . The 30 amp (main) fuse is there to prevent
the entire harness from melting down if there's a short circuit to ground (assuming there's a short before the other mentioned circuits are involved) . There should be other lesser rated fuses (or circuit breakers) to prevent the bike from stopping running, ie ; lighting circuit , accessories ,etc . Without seeing where the harness has burned wires makes helping out here kinda difficult . I would like to think
that (30 amp) fuse should have blown and prevented this damage . Unfortunately I have no specific knowledge of that model . Peter
 
Well, I just repeat what I see on the diagram (generator). It is, in fact, an alternator in my native language, too.
If what you say about how power is routed on the bike is 100% correct - please, let me know the functions of the terminals on the alternator:

Screenshot 20230711 003158

Maybe I am confused about what the G and B terminals provide. Thank you much!
Peter
 
.... and this Breva 1100 diagram is not publicly available anywhere, I take it?
Well, I got my diagram from a site here in Europe and, I guess, I will finish what I started anyway.
What format is this schematic here? Vector or bitmap? Anything in addition to colour wires (layers, etc.)?
Thanks!
 
I think you will find "B" goes directly to the battery and "G" goes to the ignition switch to supply power to the rotor. There is no internal fuse in the alternator. If its connected up incorrectly the diodes blow, so thats a sort of fuse.
 
john zibell said:
It is a .gif file. What is your time worth to create something that already exists?
Click to expand...
Unless that .gif file is of very high resolution this Breva schematic, being quite large, must be illegible. I have seen such diagrams before and they frustrated me greatly. The format I started with was PDF and it scaled very nicely (in my case to A2, which is 16.5 x 23.4 inches for those of you using the imperial standard). This is the advantage of vector graphics.
I am now in the process of editing it with Inkscape and - when done - I will post my work back where I got the PDF from as my contribution to the community.
 
I do not mean the starter motor, inside an alternator is a "rotor", voltage is fed to the rotor via carbon brushes and 2 slip rings, this is what produces the electromagnet whos lines of force cut the stator and produce the output current, this is in turn controlled by the inbuilt regulator.
 
Oh yes, I see. Understood now. Thank you so much, Kevin.
Given the above, I shall answer my original question (in the title of this thread): indeed, the output of the alternator is protected by the main fuses (parts 24 on the diagram). Interestingly, if one shorts the power outlet (part 27) the current will flow unrestricted (unlimited) as long as the alternator produces power. Will it be quick to shut it down (by means of disappearing field current, or excitation current is a more proper term here?) when there is a short anywhere on the power rail in a vehicle?

In my case, it was not fast enough, or a 30A fuse (main fuse, part 24) was simply rated too high to prevent this:

uc


This is the headlight connector. Similar damage occurred at the ignition lock switch, but I haven't found a good explanation for that one (yet). The short was caused by a pinched wire inside the headlamp. This whole mess started when I activated the high beam.
 
Last edited:
pswiatki said:
Unless that .gif file is of very high resolution this Breva schematic, being quite large, must be illegible. I have seen such diagrams before and they frustrated me greatly. The format I started with was PDF and it scaled very nicely (in my case to A2, which is 16.5 x 23.4 inches for those of you using the imperial standard). This is the advantage of vector graphics.
I am now in the process of editing it with Inkscape and - when done - I will post my work back where I got the PDF from as my contribution to the community.
Click to expand...
When you click on a section of the schematic, it enlarges. Then you move the view.
 
pswiatki said:
Oh yes, I see. Understood now. Thank you so much, Kevin.
Given the above, I shall answer my original question (in the title of this thread): indeed, the output of the alternator is protected by the main fuses (parts 24 on the diagram). Interestingly, if one shorts the power outlet (part 27) the current will flow unrestricted (unlimited) as long as the alternator produces power. Will it be quick to shut it down (by means of disappearing field current, or excitation current is a more proper term here?) when there is a short anywhere on the power rail in a vehicle?

In my case, it was not fast enough, or a 30A fuse (main fuse, part 24) was simply rated too high to prevent this:

uc


This is the headlight connector. Similar damage occurred at the ignition lock switch, but I haven't found a good explanation for that one (yet). The short was caused by a pinched wire inside the headlamp. This whole mess started when I activated the high beam.
Click to expand...
Guzzi has a habit of using the smallest gauge wire they can get away with. The main fuse should have blown, but the wire couldn't handle the current draw, but the fuse could.
 
john zibell said:
Guzzi has a habit of using the smallest gauge wire they can get away with. The main fuse should have blown, but the wire couldn't handle the current draw, but the fuse could.
Click to expand...
Precisely my point. That particular circuit is not properly protected (with a sensibly rated fuse). It just cannot be expected that any of those wires, except, perhaps, the charging circuit, could handle anywhere near 30A in case of a short someplace. The headlight would be the prime example. It puzzles me how they did, in fact, protect several things with fuse A, including the lights...... relay coil:

Screenshot 20230711 144658

What about the lights (i.e. halogen bulbs) themselves? I don't see any protection there.
But wait, there is more:

Screenshot 20230711 144831

Well, as far as I can see it is the ignition circuit itself this time - that is protected here. So, among other things drawing power, it is the actuator of the starter motor that hangs on this fuse. Very interesting. This makes much more sense that the former case of fuse A and the headlight.

In general I don't like that idea of significant currents flowing through the contacts of the ignition key switch. Looks like a lack of separation between logical circuits and power management. But maybe they just reiterated the old designs from decades ago. Plus, this is definitely cheaper than an intermediate block of relays (either the old style, with coils, or modern solid-state) switching power.
I think I once saw a "magic-box" (pure electronics) that addresses these issues nicely, but I forgot the name... Moto-gadget comes to mind, but I am not sure.
 
Last edited:
john zibell said:
When you click on a section of the schematic, it enlarges. Then you move the view.
Click to expand...
Alright, good to know. Thank you much!

In fact, it isn't exactly easy to work with the original, vector-based, diagram - the wires are depicted as thin lines with little separation between them (which, I think, is a way to show that they form a harness of the bike).
If I wanted to have a legible printout on an A2 sheet (for example), I would have to make the colour wires as thick as almost 1/8" (3 mm). A bit more than 1/16" (2 mm) would be tolerable, but I did not check all colour combinations for dual-colour wires. Some colour pairs might not be easy to identify. Now, when the wires are thickened some of them are routed so close to each other on the original (harness) that thickening would not be possible due to overlapping.
So, I am starting to realize what a pain this can be to do the whole thing properly. :nerd::nerd:
 
The CARC bikes are better and limiting current through the ignition switch. The Tonti bikes are notorious for putting too much current through the ignition switch.
 
john zibell said:
The CARC bikes are better and limiting current through the ignition switch. The Tonti bikes are notorious for putting too much current through the ignition switch.
Click to expand...
Maybe in comparison. I see CARC also putting quite a lot through the ignition switch. Will try to assess just how much. Part of my troubleshooting - I would like to discover why it burnt in that particular place instead of blowing the relevant fuse.
Perhaps, if I identify weak points - when winter comes I will work on improvements in the circuitry.
 
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