anandpatel27
New Member
i want to control the phase angle of the triac by ic moc3041. is it possible to vary the phase angle by PWM output of the microcontroller.?? what shound be the input to the moc3041 ic?
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anandpatel27 said:thank you sir for the suggestion but could u please elaborate what is burst fire control . have not heard of it before..
Nigel Goodwin said:It's the standard way of varying the power of a heating element - you turn it ON for a while, then OFF for a while - the ratio of the two is the power you're applying to the load (it's basically slow PWM).
So if you had a 1000W heating element, and you turned it ON for 5 secs, then OFF for 5 seconds, the load would receive 500W.
The thermal inertia of the element or load smooths the pulses out.
An obvious way to do it with AC mains to count the number of mains cycles, and turn ON and OFF accordingly.
ronsimpson said:Anandpatel27,
1) If you control the phase angle of the SCRs you are switching an inductive load on/off.
2) If you use Nigel’s method of PWM at a frequency of 0.1 hertz you are switching an inductive load on/off. This method is used in ovens and stoves. It has been used before you were born.
3) You might consider switching on/off faster. One cycle on, one cycle off, two on, one off etc. Do not switch on for ½ cycle!
Method 2 & 3 use zero crossing and have low loss. All three will work to control the temperature.
Hero999 said:A fully loaded transformer isn't very inductive, it behaves more like a resistor.
If you're worried then switch the secondary or use a snubber network.