Relay contacts are fusing

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newhobby1

New Member

• Aug 2, 2010

• #1

Hi,

I'm having problems with relay contacts that are fusing and failing prematurely.
The relay is similar to G5L.
I'm using 12VDC coil and switching a 400W lamp ballast at 110V.
The relay is rated to 10A, but I think due to the induction caused by the ballast, the contacts are arcing and fusing when they open up.
Am I in the right path?
If I use a RC snubber, would that work?
Where can I find one of those one package RC snubber, instead of buying capacitor and resistor separately?
Does anyone have any input for me?

Thank you in advance.
RI

 

RCinFLA

Well-Known Member

• Aug 2, 2010

• #2

You are not going to put an RC snubber for 400 watts. A capacitor may be the simplest solution. Make sure the cap is 600v to 1000v rated or you might blow it out.

 

N

newhobby1

New Member

• Aug 2, 2010

• #3

Would you be able to explain to me the reason why not RC and just C?
I was thinking of something like this link:
https://www.redlion.net/Products/Groups/NoiseSuppression/SNUB/Docs/12027.pdf
The prefered application in the little diagram.
Would you also be kind to explain why it has to be 600v to 1000v?

Thank you,
RI

 

crutschow

Well-Known Member

Most Helpful Member

• Aug 2, 2010

• #4

RCinFLA said:

You are not going to put an RC snubber for 400 watts. A capacitor may be the simplest solution. Make sure the cap is 600v to 1000v rated or you might blow it out.

Click to expand...

Of course you want a small resistor in series with the cap. Otherwise the surge current from the cap through the contacts will fuse the contacts rather than protect them. Look here for more info.

 

ronv

Well-Known Member

Most Helpful Member

• Aug 2, 2010

• #5

Try Mallory 504mo2qa100 available at Mouser Electronics - Electronic Component Distributor

 

N

newhobby1

New Member

• Aug 2, 2010

• #6

It cannot be found.
Can you confirm that mouser part#?
Also, if I were to use a SSR, would I have the same problem?
Would I need to use a RC snubber too?

 

D

Diver300

Well-Known Member

Most Helpful Member

• Aug 2, 2010

• #7

The problem could be too much capacitance in the lamp ballast. You haven't said what type it is, but there may be a big inrush current, which would cause the contacts to weld when closing. If you put one of these in series EPCOS|B57238S100M|THERMISTOR, NTC, 10R, 5A | Farnell United Kingdom, the inrush current will be far smaller.

 

mvs sarma

Well-Known Member

• Aug 3, 2010

• #8

please have a look at this pdf file
it gives ready answers up to 5 amps and the formula also at the end

 

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Last edited: Aug 3, 2010

ronv

Well-Known Member

Most Helpful Member

• Aug 3, 2010

• #9

Link to the part itself. I think i put in an o instead of an 0.

504M02QA100 Mallory Snubber Film Capacitors

 

mvs sarma

Well-Known Member

• Aug 17, 2010

• #10

ronv said:

Link to the part itself. I think i put in an o instead of an 0.

504M02QA100 Mallory Snubber Film Capacitors

Click to expand...

for your load of 5 amps , 100 ohm series resistor might be too much
this spark quench , if wired between in put and the load pin of the contact, would allow the AC voltage through even when the contact is OFF. please check that it should not become an issue.