Br1
Newbie level 4
Good day to all.
I need to control the power to a 12V 1000W heating resistor using phase control (firing angle). Also, the power must be ON for 200ms and rest (OFF) for another 1000ms or so. This timing is controlled by PLC and the angle by a manual potentiometer. The 12V are obtained from a big 220VAC/12VAC transformer.
So I need to combine phase control with an "enable" signal from PLC. I'm using the attached circuit.
All goes well when the firing angle is large (Low power). But after a certain point when I ask for more power, Triac remains ON even if the 24V signal from PLC is OFF. If the requested power was not too much, you can turn the POT back and regain control. If it was too much, the Triac may get damaged, MT1 and MT2 get shorted, and the heating resistor catches fires and burns.
I think that the inductive nature of the Triac's load is giving me problems.
Any ideas? Sadly, I don't have access to an oscilloscope.
Maybe another circuit arrangement.
Thank you so much for any help/suggestions. This has been driving me crazy for weeks now.
Regards,
Bruno.
I need to control the power to a 12V 1000W heating resistor using phase control (firing angle). Also, the power must be ON for 200ms and rest (OFF) for another 1000ms or so. This timing is controlled by PLC and the angle by a manual potentiometer. The 12V are obtained from a big 220VAC/12VAC transformer.
So I need to combine phase control with an "enable" signal from PLC. I'm using the attached circuit.
All goes well when the firing angle is large (Low power). But after a certain point when I ask for more power, Triac remains ON even if the 24V signal from PLC is OFF. If the requested power was not too much, you can turn the POT back and regain control. If it was too much, the Triac may get damaged, MT1 and MT2 get shorted, and the heating resistor catches fires and burns.
I think that the inductive nature of the Triac's load is giving me problems.
Any ideas? Sadly, I don't have access to an oscilloscope.
Maybe another circuit arrangement.
Thank you so much for any help/suggestions. This has been driving me crazy for weeks now.
Regards,
Bruno.