Triac failure modes

We've had problem lately with the same starter coil burning out repeatedly. This is a pretty new CLX system with Flex I/O and Tell a mechanic* starters. The last coil replaced lasted less than a day. I don't know exactly how many have been put in but, two in a very short time like this tells me it's not the coil that's the problem.

My question is: Has anyone seen solid state outputs fail in such a way that they would cause coils to burn up? I've only ever seen them fail in a 'always on' or 'always off' mode.

Some speculate that starting and stopping would cause this but this starter doesn't cycle any more or less than its neighbors.

Thoughts?

* Telemechanique

Perhaps the armature is not being pulled in completely, causing the coil to overheat? I would look for a mechanical problem with the armature.

beerchug

-Eric

P.S. I love the tele nickname. I'm a big fan of tele stuff, but that's still funny!...

Eric Nelson said:

I would look for a mechanical problem with the armature.

Click to expand...

Been there, done that. Night before last the entire unit was replaced with a non-critical one pulled from a remote cabinet.

I've been thinking. I may have to bite the bullet and log on to this newfangled CLX thingy. I suppose it's possible that the logic could be cycling the coil to death.

Eric Nelson said:

P.S. I love the tele nickname. I'm a big fan of tele stuff, but that's still funny!...

Click to expand...

Yeah, ain't it just amazing what a little rearranging of sylobble emphasis and vowel reworking can do?

Tell a Mechanic...good one and it definitiely fits.

We removed all Telemecanique starters, pushbuttons and switches at the plant in TN. NONE of their devices are reliable or operate for a decent period of time.

Western PA re-arrangement OT

Another one, from the old days of Numa Logic and WDPF:

Westinghouse ...
We sting youse(*) (We sting you)

(*) Youse. (n.) Western Pennsylvania expression for a group of persons. ex. "Are youse going to the movies tonite?"

thing to check

I had a strange situation with a contactor a few months ago...
kept burning up the output device in the PLC...

Turns out that we were using DC outputs to energize DC coils
on the contactor, and the wiring guy didnt notice that there
were three terminals for the coil wiring, ENERGIZE - HOLD - COMMON.

You didnt say if you were using DC or AC, but, this is
a nice thing to know, if you are using DC.

If you keep the ENERGIZE coil on too long, the output will
draw high current. Eventually, the coil (and PLC) will fail.

Re: thing to check

jdbrandt said:

You didnt say if you were using DC or AC, but, this is
a nice thing to know, if you are using DC.

Click to expand...

Alas, it's all 110vac. Nice tidbit to file away tho'.

jdbrandt said:

(*) Youse. (n.) Western Pennsylvania expression for a group of persons. ex.
"Are youse going to the movies tonite?"

Click to expand...

I knew a woman years ago from out that way who always said 'yooinz'. Substitute wherever 'youse' is used.

Just as an addition to the DC contactor terminal thing. The wire to the Energize terminal typically goes through a NC contact of that same contactor while the Hold is applied normally. A large inrush will happen on the Energize until the armature pulls in at which point it is disconnected and the much lower Hold current is enough to keep the contactor energized.

Now, you ask, why don't AC contactors have this? In a way they do. When the AC first applied to the coil it is at a lower inductance. There is a significant current flow pulling in the armature. The presence of the iron core changes the inductance of the coil increasing the impedence significantly. The current is reduced to to a lower holding level by this. This is why an AC contactor which may not pull in all the way due to an obstruction of some type will pull excessive current and possibly burn up itself and the actuating device. Many times you'll also get the 60 cycle buzz (at least in the US).

We've expireenced Doug's proplem with S&S starters and contactors. The armature will operate properly 100 times and then it will get ****ed and not pull in all the way, burning up the coil. The mechanic replaces the coil, and tests it 25 times and leaves. Then we get the same call a week later...same issue. We went to Arrow-Mat. Cheaper and less problems.

If your applied voltage is good, what else could it be?

Check supply voltage
I have had life problems with hydraulic coils that turned out to be high (127V as opposed to 115V) supply voltage.

The supply should be the same as everywhere else in the building. I'll put a meter on it anyway. I checked it last night with a 'voltprobe', admittedly nowhere near as accurate as a meter.

I thank youse for all the replies.

Previous shift checked the voltage - 117vac. Coils draws 200ma.

The last coil installed has lasted two days now. Bad luck maybe?

Bad 'lot' of coils maybe. You finally found one from a 'day shift' production run...

beerchug

-Eric

The armature will operate properly 100 times and then it will get ****ed

Click to expand...

Nice way of putting it.

I would look at the voltage rating of your coils, and the voltage drop across the PLC output.

Because Telemecanique devices are sold world wide they offer many different coil voltage and frequency options, some of which can lead to trouble. It is very common to find coils which are rated for 110V 50/60hz (suffix code F7) rather than 120V 50/60hz (suffix code G7).

According to my Tele catalog the coils are rated for .8->1.1 base Vac for pick up and .3->.6 base Vac for drop out. Also, the standard contactor is rated for 3600 operations per hour and 15 million mechanical operations.

Note to Ron: I am sorry you had bad experiences with Telemecanique devices. Tele is to the international control world what AB is to the US PLC market. I have used their controls products as my preferred line for almost 10 years now.