Hi , how can I use some low power AVR z(chinese) to control external high power triac operating a AC generator of 50KVA TRIFASE.
I am thinking use some opto-triac , connect diret to AVR. Some help ?? Thank all. (Sorry my english i am brasiliano )

 

Post triac datasheet.

 

Use an SSR ( Solid State Relay)

Bob

 

Use an SSR ( Solid State Relay)

Bob

Or more likely three SSRs if it's three phase power.

 

OK Thank you for your help, but I think that SSR wont solve my problem, because I have to control the excitatriz from the generator, and it inclued to control this DC power ( E & I ) coming from the AVR , from 0 volts to 90 dc volts and from some miliamps to 25/30 amps. This is why I want to preserve my external hight power triac . This cinese AVR (8Amps) can control this generator, keeping tension and current well, but only to max of 8amps, and I need more, because my generator is a 50KVA, I don't use all power but some close to 22/25 KVA, and to generate this power I need more DC power coming from the AVR.. I hope that I could explain my problem well . tks

 

For sure you should use isolation. System noise due to the HV and high
currents will be challenging to keep AVR running non stop. And fault design.

Challenging design I think.

Bypass caps, consider polymers and MLCC on AVR, maybe even ferrite bead.

Regards, Dana.

 

Thank you all , I will try fixing my ac generator just today using these tips. thanks thanks

 

OK, I discovered that an AVR is an Automatic Voltage Regulator that somehow is supposed to keep the output voltage of a generator set fairly constant. I believe that it does this by controlling the field current in the rotating field. So how is a triac going to control a DC power signal? And for your generator to deliver 50KVA how much field excitation does it require? One of the very first steps in solving most problems is to determine just what that problem really is, and this is not an exception. How much excitation does the generator need, and where does this higher voltage come from. OR, is the exitation voltage supposed to be AC? Triacs work with AC, not DC.

 

OK, yes almost Ac generators works like you said, but my problem is that the old AVR board fail and I don’t have schematics to try to make some repair, so, I bought a new AVR , from chine, and this new AVR can provide only 8 amps and I need more.( to get full power I need 45 dc volts and 100Amp)

I have high power triac and high power diode installed, and they are good. So, I am trying keeping those high power triac/diode but using this lower power AVR only to control the power to excitation in order to get those 40/50 KVA power and 220VAC stable. I know that triacs works with AC , but I have a big diode serial to triac making a half wave and the excitation is done like this.

 

OK, so what you need is a circuit to vary the trigger angle of the triac to control the output of the big generator. Unfortunately I am not the one to design that circuit for you, BUT there are some other folks who have done that sort of project and possibly one of them could help you.
But there is another option, which is to use that 8 amp output from the new automatic voltage regulator to drive some power transistors to control the field current. If you still have the failed control board you could find the type numbers of the transistors used before and a new design could use the same type. The design of that part should be simple. Perhaps Wendy can contact the right person to give that design.

 

Ok tks , i did almost all , checked all transistor (just 2) , replace zenner, diodo , capacitor , variável resistor ( trimpots , but the generator still bad, I got those 220 volts ac .....but flickering. IF I use the chinese AVR I can control tension and no flickering, but i can not use all power i need. But I Will try to design myself some circuit to control the power triac , using optotriac or rc circuit plus diác, as a dimer . Lets see if will work. Thank you.

 

You are aware that the control of the triac must control the timing of the trigger for each cycle, which is a lot different from controlling the excitation current. If you use that 45 volt 8 amp output from the Chinese controller to drive some power transistors then you can have the 90 volt excitation for the field. Probably using bipolar transistors since the controller can provide 8 amps of drive current.

 

Really, all that you need is a simple power stage so that with the 8amps from the new AVR you get around 40 to 50 amps excitation for the generator field, AND you will need a DC power supply for that level of current. You mentioned 25 to 30 amps excitation originally, that is much more reasonable than 100 amps.The problem, as always, is where to get the field excitation before the generator is producing power. Was the source of the excitation current part of the failed control board, or did it come from some separate power source.?????

 

Really, all that you need is a simple power stage so that with the 8amps from the new AVR you get around 40 to 50 amps excitation for the generator field, AND you will need a DC power supply for that level of current. You mentioned 25 to 30 amps excitation originally, that is much more reasonable than 100 amps.The problem, as always, is where to get the field excitation before the generator is producing power. Was the source of the excitation current part of the failed control board, or did it come from some separate power source.?????

 

Whatever response was supposed to be shown in post #14 did not appear, only the quote of my post, #13 shows.

 

Yes you are all rigth, i do not need 100amps . 1/4 Will be ok. All power for exitation came from the generator , and i must use the AVR to control the tension 220. Because whem the generator is running i have diferents loads . And this loads makes some variations on the 220vca. I am trying to use this new AVR because it have some new protection, and this can save my gen. for ex: when the diesel engine loose rottation , the frequency comes down the AVR turn off.
. My really problem is being able to control the output window using external diodes and triacs bouth mounted on large heat sinks. I agree that by using transistors I can triger the power triac and control the voltage of the generator. I'm testing this solution because I really need to have control of the phase angle and the output of the new AVR only provides DC currents.
Parallel to this attempt to use the new AVR, I am studying a way to recover the old AVR. That is working and regulating the voltage, but the lights are flashing and the voltage in the exitatrz is a bit high. Thanks for your help, if you have other tips, please send me.

 

My suggestion was intended to be that the DC control output from the new AVR would in turn control the power transistors to control the excitation current directly. They would serve as one more stage of amplifier gain to provide up to 30 amps at whatever voltage that required. So the big question then is about the supply source of the excitation from the previous controller. OR, was that source generated within the controller? Is there any other power supply aside from the generator being controlled?

 

Okay, thanks for the idea. It might work, I'll do a test. I had not yet tried to do this because the service manual of the new AVR mentions DC output of 0-120 volts and so there is no way to trigger the triac in phase cycles. There is no other external source, the generator itself activates the AVR that by its command controls the exitatriz. But I will test and return with a response.