Triac

[edgeliving]

Hello!

Anybody heard of that a Triac could "jam" so it's always open. But only does this sometimes? So if You don't give the gate any V, the triac acts like it has V anyhow, but only sometimes!?

Thanks for help.

 

[Sebi]

Yes, when coming spikes from AC line, the triac can firing for a half period randomly. This thing depend from dU/dT ratio. The RC or MOV sometimes help (parallel with MT1 and MT2).

 

[edgeliving]

Ok!

The triac commands a motor 230 vac. A person told me that his motor was running all the time for several minutes (until he unplugged).

But i cant get the triac to do the same thing :/

Pherhaps the processor went nuts or the moc?

By the way its a Triac BT139 And MOC3081.

Do You think its safe to use the components without replacing any?

Thanks for your help.

 

[Sebi]

The motor is a brush-type? If yes, it can generate continous spikes... If it is an older, good working circuit and now malfunction, possible failure of MOC or triac also.
Anyway, i use always two antiparalel SCRs for inductive loads without problems.

 

[edgeliving]

Ok! Thanks alot for Your help!