burned triac in motor application

[mkrupi10]

I am trying to control window shadings with motor and triac circuit.
Everything seems to work until limit switch in motor module turns off motor. At that moment the triac in my circuit gets half burned(conduct current in one dirrection, without trigger signal).
Any idea what couses this?
Motor is something like that:
**broken link removed**

Circuit schematic:

 

[badea]

hi,
your schematic not clear enough to understand your problem, if you show us a full schematic it will be good.
anyway, in inductive loads as motors you should add a parallel snubber circuit (R,C) with triac to save it from high dv/dt and to prevent currents from flowing.
you can put a high speed fuse to protect your triac from blowing.

regards,

 

[Akanimo]

Hi mkrupi10,

Just like badea had said, you need some RC snubber to protect the triac from surge voltage and consequent high current that goes with sudden collapse of inductive load power.
In fact, below is a part of the MOC3023 datasheet with typical circuit for inductive load control.



With this you should be fine.

--Akanimo.

 

[FvM]

Overvoltage of inductive loads can easily cause self-triggering of the MOC3020 or the main triac. Although this doesn't regularly destroy the triac, it may have caused a chain reaction in this case by firing both triacs and shorting the motor capacitor between "up" and "down" motor terminals. Its stored energy is possibly beyond the fusing level of a small triac. The suggested snubbers will hopefully prevent self triggering.

The other option is that limit switch contact arcing caused a malfunction of the control circuit, resulting in simultaneous firing of both triacs.

 

[schmitt trigger]

What are the Triac's ratings? Please post.
For 230V applications, the rating should be at least 400 volts, although 600 volts would be even better.

An MOV protector will offer an additional protection layer, as will some fuses.

 

[mkrupi10]

Its in schematic:
https://www.onsemi.com/pub_link/Collateral/MAC4DHM-D.PDF

 

[badea]

Its in schematic:
https://www.onsemi.com/pub_link/Collateral/MAC4DHM-D.PDF

This is datasheet, we need to see a full schematic to help you