circuit for voltage regulator using triac

Post
02GF74
Senior Member
2008/07/08 06:15:59
anyone know of a good "circuits" website?
 
I am looking for a triac based voltage regulator for a car - basically the circuit will control the current to the car's alternator stator to limit votlage (if that makes sense)
 
a long shot but ......
ste5442
Super Member
RE: circuit for voltage regulator using triac 2008/07/17 04:22:51
Triac based hey?
Can you rectify the AC from the altenator first and deal with DC?
Let me know more info about what you want to achieve and I will take a look.
 
If you are looking for a good 'example circuits' site then take a look at http://www.epanorama.net/
 
S.
02GF74
Senior Member
RE: circuit for voltage regulator using triac 2008/07/28 02:18:03
the cricuit I have is in a motorcycle manual and I am not sure it is correct.  from memory the way it is descrivbed as working is by haveing 3 triacs (3 phase alternator) that are turned on/off to limit the voltage - there is a separate 6 diode bridge rectifier.
 
I will get more details of what I have so far.....
02GF74
Senior Member
RE: circuit for voltage regulator using triac 2008/09/16 07:15:19
ok, here is the circuit, the lower one.
 
I have a vague ideaof howit is supposedto woek but donllt t hink it is right as surely when the zerner supplies enough voltage to all 3 gates,then Th3 will be shorted to ground!!! surely that is wrong.
 

dchisholm
Super Member
RE: circuit for voltage regulator using triac 2008/09/16 14:49:07
ORIGINAL: 02GF74

. . . when the zerner supplies enough voltage to all 3 gates,then Th3 will be shorted to ground!!! surely that is wrong.
That does not seem like a smart way to regulate, but it appears to be what they are doing here. 

The automotive alternators I'm familiar with regulate the output by adjusting the field (rotor) current.  Does this alternator have an externally accessible field winding?  If not, I'm guessing it might have a permanent magnet field, or internally tap a stator winding(s) to excite the field.

Hmmm . . . maybe that's your answer.  If the field excitation is tapped off the stator, then shorting stator windings (as your circuit shows) would remove the field excitation and reduce the output power.  It still strikes me as a pretty klunky way to do it, though.

Dale
post edited by dchisholm - 2008/09/16 15:52:36
02GF74
Senior Member
RE: circuit for voltage regulator using triac 2008/09/16 23:51:12
it is motorcycle alternator that I'm pretty sure uses a magnet.
 
some googling shows the zener/thryristor circuit is what is know as crowbar  circuit both zener and thyristor are tied to the supply voltage - so when there is sufficient voltage across the zener, the gate is turned on shorting the supply to ground thus protecting the circuitry - usually there is fuse before that is sacrificed.
 
what is puzzling me about this is that zener is tied to 12 V - the battery but the thyristors goes to each phase of the alternator, which  think  can be as high as 30 V AC.
 
I don't know the value of the zener diode voltage.
 
ratbag_359
New Member
RE: circuit for voltage regulator using triac 2008/09/19 01:05:48
ORIGINAL: 02GF74

it is motorcycle alternator that I'm pretty sure uses a magnet.

some googling shows the zener/thryristor circuit is what is know as crowbar  circuit both zener and thyristor are tied to the supply voltage - so when there is sufficient voltage across the zener, the gate is turned on shorting the supply to ground thus protecting the circuitry - usually there is fuse before that is sacrificed.

what is puzzling me about this is that zener is tied to 12 V - the battery but the thyristors goes to each phase of the alternator, which  think  can be as high as 30 V AC.

I don't know the value of the zener diode voltage.


from what I have seen from the diagram the circuit is a basic charge regulator (chopping regulator) the thyristors are activated by the zener diode when the battery voltage reaches 13.8 (the voltage to charge a 12 volt lead acid battery). this system is to stop the battery from been over charged.
hope this clears up your question.
post edited by ratbag_359 - 2008/09/19 01:20:51