I need help for triac driving

[mesuthh]

Hello people;
I really need help friends
I am tring to drive a single phase (230V AC) motor 4A with BT137(8A), but triac gets hot like 35 celcius degree (even I am using cooler) and after some switching it is getting failed. So that later on I have changed the triac with BTA41(40A) and bigger cooler, but it is still hot around 30 degree, and in one week BTA41 also gets failing. I am tring to drve the triac with Moc3041, and I am tring to switching the triac when 5Vdc available on Moc3041.
I have tried to use snubber but it is not solving the problem
you can reach the view of my circuit on **broken link removed**

here I am triying drive the motor with 5V dc control to moc3041 so triac fries and the motor starts, and one more think I am also drving a 25uf 400 V capacitor (paralell with the motor) with that motor for compansating

if someone has an advice I will be really thankfull to him/her
Regards

 

[carmusic]

you should heatsink the triac and add a snubber network since you are driving an inductive load

 

[mesuthh]

I have used a typical heatshink but it did not solved so I have used a bigger heatshink (5cmX5cm) and also snuber has done. do you have an other advice
Regards

 

[OldTechie]

You're using a standard triac to control a highly inductive load. Triacs are prone to commutation when used in this way, that is, when the driving voltage changes phase, the inductance of the motor continues to drive current through the triac. This results in a high dV/dT effect when the current finally stops flowing from the motor, exceeding the dV/Dt rating of the triac.
A better component for this application would be a triac specifically made to drive motors. Google for Alternistor and you should find lots of info. Alternately, you could use two SCRs in inverse parallel to control the motor. (This is basically what an alternistor is).
There are commonly available from distributors such as Mouser, Digikey and Newark.

Hth,
Dave M

 

[mesuthh]

You're using a standard triac to control a highly inductive load. Triacs are prone to commutation when used in this way, that is, when the driving voltage changes phase, the inductance of the motor continues to drive current through the triac. This results in a high dV/dT effect when the current finally stops flowing from the motor, exceeding the dV/Dt rating of the triac.
A better component for this application would be a triac specifically made to drive motors. Google for Alternistor and you should find lots of info. Alternately, you could use two SCRs in inverse parallel to control the motor. (This is basically what an alternistor is).
There are commonly available from distributors such as Mouser, Digikey and Newark.

Hth,
Dave M

Dear Mr. Dave M;
firstly let me say thank you very much
which kind of scr do you advice me to make my own alternistor, because I am not a professionel on power electronics
regards

 

[SABorn]

You could ditch the triac circuit and buy a solid state relay made for this sort of application.
Much easier to mount up and heatsink as often with a triac the tab is live which can cause problems with heatsinking if care is not taken.

SSR are rather cheap if you look on ebay.

Pete.

 

[OldTechie]

I recommend that you just get an alternistor to control the motor... It's a single device and costs less than two SCRs with their associated triggering components.
A Littelfuse/Teccor Q8016LH2 (Isolated base) or Q8016RH2 (Non-isolated base) should handle your motor easily. It's a common part; should be available from many suppliers. Datasheet is here https://www.electro-tech-online.com/custompdfs/2011/01/Littelfuse_Thyristor_Qxx15xx_Qxx16xHx.pdf.
You should be able to use the MOC3041 as in your original post. You might remove the 220-ohm resistor for more reliable triggering.
Cheers,
Dave M

 

[cobra1]

Take out the 220ohm resistor and see if there is a difference, i am using a BTA08-600 in this way and i am able to drive some pretty good loads, i even managed the get it to heat a 1kw heating element once with a good heatsink on the triac

 

[mesuthh]

Thanks to all advices
regards

 

[gelecg]

I have driving 2.2 HP single phase ac induction motor with capacitor like you.
AND bta41 failing.

snubber and zero crossing is correct.but bta41 in full load suddenly failed.

can you help me?