TRIAC MOTOR CONTROL

[mwolff]

I am controlling a 220v AC 1/8 HP motor with a TRIAC circuit. When the TRIAC goes off, every cycle, the 220v are applied over the gate circuit. These is a resistive circuit. I am using low power resistors (1/4 watt) with succes, but i think these resistors might burn in the future. I would appreciate if someone knows if these resistors are going to resist or if i should try another way to trigger the TRIAC. I couldn´t find any document about resistor ratings, for example peak dissipation vs time. Perhaps if i put 1 watt or 2 watt resistors that should be enough to be sure that there is not going to be any trouble, but maybe not. Thanks in advanced for any advice.

 

[Marke]

You should not be appying 220VAC to the gate circuit on a triac, i will self destruct very quickly. Do you have a circuit of what you are doing? if so can you email it to me at mark_empson at hotmail.com and I will see if I can help.
Best regards,

Mark Empson

http://www.lmphotonics.com

 

[piedade]

what kind of control are you trying to do ?
no problem in drive it directly from the mains... with a limiting resistor of course.
just see the triac specs and calculate the resistor power dissipation from the Gate current.

 

[jbartos]

Suggestion: Visit

http://www.redhouse.force9.co.uk/dexterspage/electr~1.htm

etc. for more info

 

[Nandos]

Mwolf:

Since you are not specific about your circuit it is difficult to say yes or not.
If you are connecting the resistor between the gate and the anode of the Triac then you do not have problem.
You are feeding the necessary current to turn the Triac on, that maybe in the range of about 20 or so milliamps then tehTriac fires and places just about 2 to 3 volts across the resistor.

To calculate the power dissipation, determine the Triac triggering gate current and the voltage that the resistor sees until it triggers ( this will give you the time that the resistor receives heating power), then a multiply by 120 pulses to attain the total used time .

Regards

Nando