Just a one nicely burnt contactor for you 🔥🛠️ - Page 1
Forum section: electronics / general

author: Miyuki
author_rank: Frequent Contributor
timestamp: August 03, 2021, 10:07:40 am
content: It just worked till contacts fall offSo contactor is no longer a contactor

author: AlbertL
author_rank: Regular Contributor
timestamp: August 05, 2021, 08:39:05 pm
content: Wow, that's pretty bad! What happened - was it overloaded?

author: Gregg
author_rank: Super Contributor
timestamp: August 05, 2021, 09:03:06 pm
content: The video stated the contactor is 1984 vintage; that seems pretty good especially since it appears to have seen some weather or moisture by its crusty appearance. These days it may be hard to find an equal quality replacement.What is it powering? There is what appears to be a compressor of some type in the first few frames of the video; if it powers a compressor you might want to check the unloader valve to make sure the motor doesn’t have to start under excessive load.

author: Miyuki
author_rank: Frequent Contributor
timestamp: August 06, 2021, 06:11:44 am
content: Yes it powers a huge compressor and it has no problemsJust that millions of cycles starting huge induction motor wear it

author: Miyuki
author_rank: Frequent Contributor
timestamp: August 06, 2021, 08:30:36 am
content: Quick repair video

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: August 06, 2021, 09:48:18 am
content: Nice.It failed very gracefully. Contactors often don't go down without a fight.

author: SeanB
author_rank: Super Contributor
timestamp: August 06, 2021, 11:00:43 am
content: Still got the original Brown Boveri star delta timer in there, with the pneumatic delay unit on it as well, though I do suspect that the delay unit has a failed diaphragm by now, the rubber is not going to last forever. Contactor with the contacts burnt off is a common failing on this old range, and the contact replacement kits are long discontinued as well, as they are considered a service part. For the failed 16A 3 phase unit I would recommend using the 25A frame size units, the larger contacts will last longer, and likely the failure would be the actual armature core finally flowing with time till it binds with the case, the original is likely half way there, but the contacts wore out first. Mechanically those contactors will easily do fifty million mechanical cycles, and at full load easily 2 million cycles, though only with a pure resistive load. Big inductive load probably was around the 50 thousand cycle mark when it failed.If that is a 3 phase motor best thing is to add on an overload relay to the contactor, as that, in addition to overcurrent protection, also gives phase loss protection, in that if one phase disconnects the differential heating on the other 2 phases will trip the overload out, and for this you probably want it to be manual reset as well.

author: LECKO
author_rank: Newbie
timestamp: August 10, 2021, 06:50:41 pm
content: Years back, in the mid 1970's I was a district electrician at Boulby mine in the UK. I got a call from a Joy under cutting machine operator that his machine was smoking from the control chamber.It sure was and had tripped the power off.These machines were powered by a trailing cable and were 1.1Kv, 60HP cutting head motor and 25hp hydraulic pump motor if memory serves me right.I opened the control chamber, and my jaw dropped, wasn't much left in there but molten metal, melted plastic and a thick layer of carbon.There used to be a double contactor, reversing and forward, mechanically and electrically inter locked, used to be that is!! Even thinking back, there wasn't enough left to diagnose what had happened. Obviously it had been a sudden short circuit, but how??My Foreman came to have a look, he too couldn't come up with any ideas why it had happened, but that's the nature of electrical breakdowns, most of the time we could diagnose what happened, but the odd occasion left us high and dry as to what happened.

author: elekorsi
author_rank: Regular Contributor
timestamp: August 10, 2021, 07:40:15 pm
content: Quote from: Miyuki on August 06, 2021, 08:30:36 amCorrect me if i am wrong, but i think that those instalation contactors are not rated for AC-3 operation. If so, it will be dead soon...Should use some proper AC-3 industrial contactor...

author: Miyuki
author_rank: Frequent Contributor
timestamp: August 11, 2021, 11:23:06 am
content: Quote from: elekorsi on August 10, 2021, 07:40:15 pmIt has AC1/AC7a 25A/16kW it is comparable to a 3kW motor loadAnd in near future (year or two) will be replaced with VFD anyway