Triac for AC motor speed controller

Bordodynov

Joined May 20, 2015
3,426
Two reasons causing a current surge. If the connection fails (this is when the voltage of the power supply is important at the moment of connection, then the triac turns on automatically.) The method of combating this is the connection between the control leads of the resistor (in my scheme it is R4 = 51 Ohm). Another source of the initial throw can be an additional circuit , consisting of a series-connected capacitor and a resistor R3 and C3.Methods to combat the harmful effect: 1. Add a 51 ohm resistor 2. Transfer the capacitor with a resistor in parallel to the input terminals of the diode bridge.
 

Thread Starter

q12x

Joined Sep 25, 2015
2,227
Ok, the 58 ohm resistor (in my case) did the job of running the motor and not letting it stop as before.
Thank you!
Now...
I put a lower value pot this time, since i dont have 200k pots in my scraps or at store. This one was a 75k.
I literally watched the pot burning every step i made while rotating it. Big sparks and a thin smoke. I have more smaller values pots that i can test with.
I switched the Snubber RC block in front of the diodes as you suggested. Before doing it, the voltage/current was a bit calmer on the pot, but now it is frying the pots like they are meat on the grill.

I suppose I must make your skeme since this one is cursed and only problems i had with it. Offff.
I was thinking to add a secondary Snubber RC in front of everything. Like it was before this change.
 

Thread Starter

q12x

Joined Sep 25, 2015
2,227
I'm definitely Not a good electronist!
The capacitor there exploded with a beautiful blue flame that made a round hole (literally) in it.
I think that is the principal suspect why i burned my scheme.
That area with the 200k pot, R1 10k and 0.22uF capacitor, is a Snubber !
But what role is having that capacitor there? It is before the gate of the triac. It is lowering the voltage down? I measured it and it was always shown 220V between the triac gate and a main terminal. It should be maximum 5V to the gate of triac. I imagine that gate snubber is like a short circuit somehow, letting 215V pass and only 5V action on the gate... this is my BEST GUESS but im not sure 100%. Putting that WRONG capacitor there, after it burned out, the 220 goes directly into the gate and practically split the triac in half.
I didnt think before, that capacitor is that important - but now i learned my lesson. Very expensive lesson!
Can someone explain to me what the hell is going on? I know some stuff, but for sure im not that good! Please be kind and tell me what is this scheme doing?
Other than this scheme... is there no OTHER way to lower down the CC 220V to the motor? Preferably with a pot. But with normal resistors is fine too.
I really want this to make it work! (somehow)
Thank you!

 
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