AC shunt regulator for a motorbike

Thread Starter

setsquar

Joined Oct 11, 2012
34
I have been asked if I could make an AC shunt regulator for a motorbike that has a permanent magnet alternator lights are 6volt 30watt max but offload the voltage can climb to 30v
no DC or battery on bike
looking online I found the photo below
but was wondering if my drawing below would work and if so what value of resistor should I use

now i cant remember how to add a photo on this forum :(
 

Thread Starter

setsquar

Joined Oct 11, 2012
34
Hi thats for your help
I have seen various circuits like in that 8page thread but they are all a bit over complicated for what is only a crude over voltage device to stop the bulbs blowing you can buy a commercial device that is I believe only a Zener and SCR
If I can work out how to upload a photo I will show what I had in mind
 

crutschow

Joined Mar 14, 2008
25,117
these are the two .jpg on imgbox
That uses an SCR to clamp the voltage to zero once the maximum is reached, which works okay for limiting charge to a battery, but not so much for limiting the voltage to a bulb.

For that you want a Zener clamp circuit or one similar to that in post #3.
The Zener circuit could consist of a high power 12V Zener in a diode bridge circuit or two 12V Zeners connected back-to-back.
 

Alec_t

Joined Sep 17, 2013
11,400
Er... perhaps not 12V. It's a 6V (RMS) system, so ~6.8V zeners would be appropriate.
 
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Thread Starter

setsquar

Joined Oct 11, 2012
34
now i have found out how to add photos
im going to try this my drawing but could someone advise what sort of value resistor to use
have included photo of what my thinking was based on
thanks for your Patience and help
SCRshunt.jpg
3Preg.jpg
 

Alec_t

Joined Sep 17, 2013
11,400
In your hand-drawn circuit the resistor value (probably in the 100Ω to 1kΩ range) will depend on both the zener voltage and the gate sensitivity of the SCR.
 

Thread Starter

setsquar

Joined Oct 11, 2012
34
In your hand-drawn circuit the resistor value (probably in the 100Ω to 1kΩ range) will depend on both the zener voltage and the gate sensitivity of the SCR.
zener voltage is 7 volt
Igt is 60mA max
Vgt is 2.5v max
but input volt can be between 7 and 25 volt ?
 
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