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Originally Posted by Mr Gazza
So will the series R/R meter power demand from the alternator and release more to the engine? Like when I disconnected the cables on my teeny bike? Or does the alternator still sap the engine whatever?
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A shunt takes full power from the alternator all the time. It maintains voltage/current to what you want by bypassing (shunting) the excess away.
An SCR shunt gets damned hot doing this. A MOSFET shunt doesn't get so hot - but is still doing exactly the same 1960's thing, just with updated semiconductors that make it more efficient/turn less power into heat.
Any drag on the motor due to the alternator will be identical with both types of shunt; the alternator is running 100% output, 100% of the time.
I thought this was a pretty clear, readable explanation, of the difference between shunt/series R/Rs from triumphrat
https://www.triumphrat.net/threads/c...upgrade.104504 - they're talking about the SH775 here:
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It does NOT appear to be suited for the high rpm 4-cylinder Triumph 600-4's (TT600, Speed4, Daytona 600/650) - at high rpm it loses regulation on those bikes.
(However see further down this thread for details on the SH847 Series R/R which has been proven successful on those models)
It is made by Shindengen and has the exact same Form Factor as the FH012/020 series MOSFET Rectifier/Regulator that has enjoyed great acclaim & success.
A couple of things to note - it has lower current spec than the FH012/020, however still plenty adequate for the Twins (the FHO12/020 is actually way overkiil re current rating requirement anyway for the Twins); it is not MOSFET but SCR.
Wait I hear you cry - "you have been espousing the benefits of MOSFET regarding the reliability of these units, why are you now suggesting a replacement SCR type?"
Here is the SIGNIFICANT difference - this new R/R is SERIES - not SHUNT!!
Why is that of benefit?
The difference between Series & Shunt is that:
Shunt - the Stator always has to apply maximum generated current - when the R/R is in regulation it shorts across the winding to 'shunt' current away from the load directly back to the stator. In an SCR (OEM) Shunt Regulator the SCRs get extremely hot and they ultimately burn out if that heat is not adequately cooled - that is why OEM needs to up front directly in the cooling path.
Because of the way it operates, if you reduce the system load (e.g. turn off the lights) the R/R will actually have to shunt MORE current and will run hotter - but the stator load is the same regardless of whether the current is going to the load, or back through the SCR's.
Series - this is fundamentally different in that in a Series design, instead of diverting (shunting) excess current back to the stator to control the output voltage, the regulation works by interrupting the current path to the load. This means that the Regulator ONLY supplies current demanded by the load itself, and no excess current parallel path through a shunt. So the net result is that this type of Regulator is MUCH kinder on the stator because the stator is always supplying much less current! So the stator does not get so hot and its reliability increases significantly.
The fact that it has SCR's is not quite so problematic as in the Shunt application, because they are flowing less current and for a shorter duration. So they will not get as hot as when used in shunt mode.
This particular unit is a Shindengen SH775 regulator and is used on Polaris models.
It is VERY inexpensive - brand new -
e.g. $73 shipped!!!! ($60 & change plus shipping)
http://polarisparts123.com/partnumber-search/ (enter 4012941)
Polaris REGULATOR-3PH,35A,SERIES,105C for 2011 Polaris R11HR76AG/AR RANGER 6X6 800 EFI 4012941
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