Hello

I'm using relay with datasheet in a link, it is R1, RT314012. I operate the relay with about 10.5 volts to turn it on. DC coil is 12V. I have no problem turning it ON. I maintain the relay in ON position with constant 6V. I have no issues keeping it ON. I have an issue where relay will not turn OFF even when voltage across terminals is virtually 0V. I tried shocking it with knocks, shorting the terminals after disconnecting the whole board from power, it has no capacitors. I use transistors to operate it. Most of the time it works but once it "latches" not even removing relay from circuit will help. I had to connect it manually to 12V battery several times, switching the polarity to return it to normal state. Funny thing is that click is always heard as it turns on/off but nothing happens. I turn it OFF from 6V to 0V dozens of times continuously but it won't turn off while clicking, while board is powered. I replaced it with new one and it operates the same.

Load on relay is 230V, couple of amps at best, maybe 2 on peak usage (LCD, two active speakers, two small switching PSUs). Circuit operates reliably. I have flyback diode connected.

Power rating is 4000VA, it has NO and NC contacts, there is almost no load on it and I wonder what could be the cause for the problem and how to solve it. I shorted pins in pairs since it has two pins for each contact but that should not be the issue. I suspect it is not meant to be ON permanently since it happens after being on for couple of minutes at least or 6V is not enough to keep it on so contacts don't make good connection and area is small so they fuse but that seems odd. I tried running 2.5kW load, motors (fan and vacuum cleaner), LED lights, phone chargers, all separately, and it will work with no issues.

Thanks.

Link to relay datasheet
https://image.schrackcdn.com/katalogseiten/k_energen6_518-524_en.pdf

 

Hi,
in my practice some ancient soviet relays do the same. Those were big in size and open type, so one's can inspect the operation of the relay. We tried to investigate this and decided that it was a factory defect. Steel was of a poor quality and remained magnetized even the coil is deenergized

 

If there is a 'click', it would indicate the armature is returning to the off state, but the contacts are sticking.
BTW, it is usually beneficial to drill a small hole in the cover if the environment allows it, some even have 'pip' in the cover in order to expose the inner working after board de-fluxing etc.

 

I investigated the issue. I took the advices and suggestions from previous posts and used cutting disc to open one of three I have to investigate the issue further.
It is a quite small device, walls are thin. I concluded that issue was I packed the device in tight space with wires pressing against the device obstructing physical movement.
The one I opened I tested on a bench and it would never stick even after hours when it did as part of the circuit in minutes, testing it as replacement, unopened. I also made sure when soldering the third one I only briefly touch the pins with hot iron and solder it to wires that were soldered to the PCB beforehand. The reason is, since the device is really small I most likely damaged the relay since I use protoboard so creating fat conducting traces requires quite some heat. All three devices now operate, two outside the circuit, one cut open.
I have decided manufacturing defect on the relays is out of the question since all three behave identically. I decided it must be an error on my side and as it turns out it was.
I hope someone else finds this post useful even if issue is simple. All the relays I held in my hands had thick solid walls and I assumed this one is well protected but as it turns out moving pars rub against "paper thin" walls since I assume it is meant for different applications and I value it for it's compact size.

 

That sure doesn't resemble the structure of the PCB relays I have used or replaced in the past!

 

It might not be a PCB relay. Automotive? It is really small for the 4kVA rating.

 

Appears to be an old Schrack model.

 

sounds like common relay issue when overloaded and contacts weld. this happens when load is too large, not resistive, etc or combination of mentioned. it also happens when relay is deformed in some way, perhaps when overheated.
that is a small relay but it is rated for 250VAC and up to 16A but that is for resistive load. if load is inductive or capacitive, even 0.5A could cause it to stick because there is much higher peak when switching such loads. adding suppression devices across loads or relay contacts can help, if not you need to choose another relay or use contactor.

 

sounds like common relay issue when overloaded and contacts weld. this happens when load is too large, not resistive, etc or combination of mentioned. it also happens when relay is deformed in some way, perhaps when overheated.
that is a small relay but it is rated for 250VAC and up to 16A but that is for resistive load. if load is inductive or capacitive, even 0.5A could cause it to stick because there is much higher peak when switching such loads. adding suppression devices across loads or relay contacts can help, if not you need to choose another relay or use contactor.

Great information. I use it to power small switching PSU x 4 two 80W active speakers. I have a scope and I can inspect but I don't have current probe. I will us contactor instead of relay since peaks from switching PSUs have to be terrible for the little device even if total current is low. Total rated current is 1 + 1.2 + 0.7 + 0.8 A or about 4A + 250Wx2 for speakers, they don't have current rating and I'm not sure 80W is their sound power or electrical power but they are not that loud, they are kind of mid range studio speakers (class of amplifiers/efficiency?) so peak current/power might be even over rated 16A.

It might be a combination of physical deformation and incorrect component selection for the load type and not just one.

Thanks all for the info.

 

It might not be a PCB relay. Automotive? It is really small for the 4kVA rating.

According to the connecting pins, that is intended as a PCB relay as well as socketed. !

 

P=I^2*R
I=SQRT(P/R)
I=SQRT(80/8)=3.16A

but that is continuous. music etc produces bursts of current that can exceed that value by quite a bit.
and since audio application, you do not want to add suppression etc as that would degrade the signal