K5 Pointy Headlight Connector Burning out

[SV650rules]

Originally Posted by Ruffy

This is correct. The semi-conductor junction has a fixed volt drop.

This is not correct. Power consumed in a component is the product of voltage dropped and current through it. P=IV. Dropping 1V at 10A generates 10x the heat of dropping 1V at 1A. (If this is not the case, why are diodes manufactured and sold with different current/power ratings?)

The larger diodes have a bigger surface area to dissipate the extra heat, the voltage drop stays the same within the current rating of the diode, after that you get thermal runaway and smoke

[glang]

Originally Posted by SV650rules

A basic thyristor is an on/off device - it can be triggered but will only turn on when it is forward biased, and it will not turn off until voltage across it drops to zero or goes reverse - an igbt thyristor can be turned off by removing gate supply at any time. a device that is in some conductive state other than fully on will dissipate a lot of heat - that is why square wave power supplies are more efficient - the switching device is either fully on or off.

Ok the wonderful internet does say that thyristors only switch but transistors can control as an amplifier so surely we have the latter in our R/R?

[Ruffy]

Originally Posted by SV650rules

A basic thyristor is an on/off device - it can be triggered but will only turn on when it is forward biased, and it will not turn off until voltage across it drops to zero or goes reverse - an igbt thyristor can be turned off by removing gate supply at any time. a device that is in some conductive state other than fully on will dissipate a lot of heat - that is why square wave power supplies are more efficient - the switching device is either fully on or off.

I agree, but I'm at my limit of component knowledge - I was simply working off the drawing symbols.
I would have expected to see a different symbol for IGBT. (I admit that I don't recognise the term "IGBT Thyristor" - I suspect it's what I know as just an IGBT?)

Originally Posted by SV650rules

The larger diodes have a bigger surface area to dissipate the extra heat, the voltage drop stays the same within the current rating of the diode, after that you get thermal runaway and smoke

Yes, agreed. Although I think this confirms the point I was making in my first challenge to you, that larger current equals greater heat generated in the diode (and vice versa)?

Originally Posted by glang

Ok the wonderful internet does say that thyristors only switch but transistors can control as an amplifier so surely we have the latter in our R/R?

Not necessarily. I think the SV OEM R/Rs are simple thyristor models, with the functional limitations you imply. Simpler devices=cheaper to manufacture.
However, your thought process is reasonable: This is essentially why those who recommend upgrades suggest MOSFET R/Rs. More complex semi-conductors but the premise is better control with less heat production and so greater performance and reliability.

However, as mentioned by SV650rules, R/Rs use a switch-mode technique, rapid full on/off switching that leads to an averaging effect in a relatively slow-responding load. Transistor or thyristor, they won't try to partially throttle current flow like a variable resistor or an audio amp would.

[Ruffy]

Originally Posted by SV650rules

A basic thyristor is an on/off device - it can be triggered but will only turn on when it is forward biased, and it will not turn off until voltage across it drops to zero or goes reverse - an igbt thyristor can be turned off by removing gate supply at any time. a device that is in some conductive state other than fully on will dissipate a lot of heat - that is why square wave power supplies are more efficient - the switching device is either fully on or off.

Originally Posted by glang

Ok the wonderful internet does say that thyristors only switch but transistors can control as an amplifier so surely we have the latter in our R/R?

glang, I just had another thought that may help you: Compare the size of the R/R (which is probably capable of dealing comfortably with up to 150W) to the heatsink on even a small size audio power amp. I think you'll find a much larger heatsink on an equivalent audio amp and this physically shows the extra heat implications of trying to variably control the power flow. Hence why R/Rs use switching techniques, even transistor regulated ones (although it does mean that the alternator coils and wiring have to take the thermal strain - there's nowt for free!)

[Bibio]

i would like to take an R/R apart to see whats inside.

i dont understand why there is no dropdown transformer to help the regulation. the whole system works exactly like a power supply except the mains is generated power.

AC power (stator) - "Rectification - DC power - Regulation" (R/R) - Smoothing Capacitor (battery). the only thing missing is a drop down transformer before the Rectification. if you dropped say the 90v AC to a more suitable 20V AC then the R/R would not have to work as hard.

[Ruffy]

Originally Posted by Bibio

i would like to take an R/R apart to see whats inside.

i dont understand why there is no dropdown transformer to help the regulation. the whole system works exactly like a power supply except the mains is generated power.

AC power (stator) - "Rectification - DC power - Regulation" (R/R) - Smoothing Capacitor (battery). the only thing missing is a drop down transformer before the Rectification. if you dropped say the 90v AC to a more suitable 20V AC then the R/R would not have to work as hard.

If you took one apart I think you'd find black electronics and a circuit board.

You're correct, it is a power supply but in this case I don't think a separate transformer would really add anything. Yes, the R/R would work less hard but the transformer would take the strain instead.

A marketing man might say the R/R was a digital transformer rather than a traditional analogue one!

You could achieve similar voltage reduction by changing the coil configuration of the alternator but there would be consequences for the winding wiring sizes, to be able to supply the same power output. (Fewer turns for lower voltage output , larger cross-sectional-area for increased current.) This has mechanical and thermal implications.

The alternator is effectively a secondary coil of a transformer and there's nothing to be gained overall by adding a second separate transformer when everything is so close together.

I think we're in to the realms of engineering compromise at a system level.

[glang]

glang, I just had another thought that may help you: Compare the size of the R/R (which is probably capable of dealing comfortably with up to 150W) to the heatsink on even a small size audio power amp. I think you'll find a much larger heatsink on an equivalent audio amp and this physically shows the extra heat implications of trying to variably control the power flow. Hence why R/Rs use switching techniques, even transistor regulated ones (although it does mean that the alternator coils and wiring have to take the thermal strain - there's nowt for free!)

Dont forget though that theres far more forced cooling available on a moving bike especially as, handily, more speed equals more heat to be dissipated.....

[Seeker]

Originally Posted by Bibio

i would like to take an R/R apart to see whats inside.

Here you go, build your own:

https://www.edaboard.com/showthread....-my-motorcycle

[aesmith]

Originally Posted by Bibio

AC power (stator) - "Rectification - DC power - Regulation" (R/R) - Smoothing Capacitor (battery). the only thing missing is a drop down transformer before the Rectification. if you dropped say the 90v AC to a more suitable 20V AC then the R/R would not have to work as hard.

The quoted 60V AC is an open circuit figure, with the AC disconnected from the RR. I would guess it drops substantially when load is being drawn.

[Bibio]

Originally Posted by aesmith

The quoted 60V AC is an open circuit figure, with the AC disconnected from the RR. I would guess it drops substantially when load is being drawn.

as far as i know it dont work like that. the AC will rise and fall slightly with engine speed but not load. i could be wrong though.