Welded relay contacts

You need a capacitor resister combination made for this very reason It is 100 Ohm res in series with a 0.1 Micro farad capacitor "Snubber network". This goes across the relays contacts the ones switching the load. This queches the spark.

You got me man! Especially if that NC contacts of the relay are floating..?.. There must be continuity somewhere to get the arc. Is the arc passing through the NC contact and jumping to another point (basically creating it's own conduit through your "floating" NC contact).

Try adding an additional relay to the supply side of the arcing relay, in essence double isolating the load from the arc point. This would be easier to understand if you had a schematic.

Good luck dude!

Or you could listen to that guy (Mr. snubber Network) who might actually know what he is talking about...

Thanks to all who replied!

I have figured it out. Latter tonight I will post a schematic and explanation.

Thanks again!

Bill12780

Hello,

Your explanation of the problem is not very clear . It is said that the NC contact is floating but it is not clear weather it is used for what purpose. If you mail me your circuit an explanation can be given. Try to connect a diode with a condenser across the NC contact and mail me he result Best of luck.

vi.abraham@gmail.com

Is this brake controlled by a solenoid or something? sounds like stored energy in an inductor is the reason for your welded contacts. Maybe its reacting with the motor inductance /capacitance.

Try looking into www.selinc.com and search for SEL9501 or SEL9502 named "arc supressor".

Then install it in parallel with the contacts.

this will probably solve your problem.

Regards

Hello all,

I have been trying to find sometime to draw up a print and a full explination of what was happening. But I have not had time to do so (work is whipping me pretty hard as of late)

Anyway to make a long, long, long story short. The Motor has two windings right...Well it was the winding NOT being used that was collecting the back emf. After watching closely I realized that the arc was comming from the un-used NC contact to the common. NOT common to NC. SO......All I had to do was cut a trace to seperate the two relays NC pins.

Thanks to everyone who responded I do appreciate all your input. One day maybe I will publish all the details for everyone.

Thanks again!

Bill12780

Hi,

I openly admit that my electrical/electronics knowledge is limited as I'm a mechanical engineer - however, I was employed by IES in Adelaide, Australia for 17 years and they produced a unique IC that was made just for this purpose. Used in conjunction with a few other components it prolonged the relay contact life of temperature controllers for cooker rings many, many times over by eliminating the spark. IES has since become Legend - but they have a US outlet that may still be IES.

Go to www.integratedelectronicsolutions.com

As far as I am aware, most motors, when shorted out (after first removing the supply) whether DC, AC or Universal, will stop almost instantly anyway......its call electrodynamic braking if I remember correctly.....an energised motor has magnetism, when the supply is interrupted, the motor produces electricity as a generator for a short time. Shorting the windings (all three in a 3 phase design) causes a massive load on the generator and stops it dead, with no off center effects, that is the bearings are not stressed as for example when a mechanical brake is not perfectly aligned!)

So you may need your mechanical brake to hold things still, but you should also be utillising this function I have mentioned as well......it will certainly cut the wear down on the brake shoes as well as providing a further means of braking if any component (electrical, mechanical or electronic) in your brake circuit fails.......!!!

This is nothing new, believe me, I learnt it over 40 years ago and it was well known then......even the Dinosaurs knew about this function I expect!!