Snubber circuit

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  • #251
Tom.G
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To put it simply, I fixed the contact race and took the 25 amps out of the braking NC'd I put to new cube relay in sweep we'll see if it changes anything. Does my idea sound OK to you?
Almost Anything that works is OK! Nice going.

But this is the first we have heard about 25 Amps as the contacts were opening. I even used the Search function on this thread and found nothing.

In general, relays should not overlap their contact timing unless specified when ordering. Can you give us the the part No. of the relay that was ordered, and/or the number on the box, and/or the numbers on the contact block? Any and all info will be helpful. Something very strange is going on.

Did you try replacing the MOV before making this change? If it failed it could/would show similiar symptoms.
In post #207 you stated the MOV is OK. But didn't answer my question in post #215 of how you checked it. An open failure may not be visible.
 
  • #252
jim hardy
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In general, relays should not overlap their contact timing unless specified when ordering.

Break before make. Both NO and NC should be unmade mid travel both directions.
 
  • #253
jim hardy
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Overlap contacts do exist in Allen-Bradley world.

bowling_overlap.jpg


When nothing will show itself wrong you have to make everything show itself right. Check a relay for overlap.

Also we had way way back a question about an extra wire..
about post 127 or 128
 
  • #254
153
7
Almost Anything that works is OK! Nice going.

But this is the first we have heard about 25 Amps as the contacts were opening. I even used the Search function on this thread and found nothing.

In general, relays should not overlap their contact timing unless specified when ordering. Can you give us the the part No. of the relay that was ordered, and/or the number on the box, and/or the numbers on the contact block? Any and all info will be helpful. Something very strange is going on.

Did you try replacing the MOV before making this change? If it failed it could/would show similiar symptoms.
In post #207 you stated the MOV is OK. But didn't answer my question in post #215 of how you checked it. An open failure may not be visible.
 
  • #255
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7
The 25 amps motor start exist at the NC opening when of course NO close due to a jumper from NO to NC. Yes there probably is an overlap but my thinking is that the 25 amps doesn't need to be at the NC's at all
Regardless of overlap. Also my thinking is that this time element that overlap occurs,
Is it enough to eliminate a chance of ionanation as the NC open? As far as checking the MOV I just checked continuity.
Tom/ Jim these are just my brain thinking trying to look at this as the sweep is running.
 
  • #256
jim hardy
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The 25 amps motor start exist at the NC opening when of course NO close due to a jumper from NO to NC.

Is that this one ?


i cant keep those contact numbers straight
bowlingsweep19A.jpg


i cant keep those relay contact numbers straight.

bowlingsweep10A.jpg


Sure sounds like those contacts overlap for some reason. How does complete relay part number break down regarding overlap contacts? That AB bulletin is brutal to work through.
 
  • #258
153
7
Is that this one ?


i cant keep those contact numbers straightView attachment 107092

i cant keep those relay contact numbers straight.

View attachment 107095

Sure sounds like those contacts overlap for some reason. How does complete relay part number break down regarding overlap contacts? That AB bulletin is brutal to work through.
That's it
 
  • #259
153
7
That's it
That's what I mean the specs for the relays are out of my league! I tried looking up relay overlap forget it!
 
  • #260
jim hardy
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That's what I mean the specs for the relays are out of my league! I tried looking up relay overlap forget it!

spec sheet didnt even mention overlap that i could find

that snip i put up showing "overlap" contacts versus "standard" came out of a selection guide that for some reason isn't in the technical bulletin / specs we've been studying . I guess they figure a contact is a contact and it's some other part that controls whether it overlaps another contact.

<Rant>Very frustrating. I never heard them called that before, i'm used to "Break before Make" not "Standard" and "Make before Break" not "Overlap".
I think motorcycle gear shifters belong on the right hand side, too. <EndRant>

Used to be when i got this confused i'd sit down with a relay and the box it came in and the purchase order for it, cross check part number versus catalog number &purchase ordwr versus what the words say about contact operation and verify that by watching the contacts move as i depress the solenoid plunger. But that was in the power plant where everything was as over-documented as military gear. As you see fr some similar relays a simple 0 or 1 buried in the catalog number changes what you get from "Break Before Make" to "Make Before Break".
Sometimes the catalog number isn't on the part because it's made from subassemblies each bearing its own part number.

Is there a picture of the relay that melts its contacts someplace in this thread with a part number on it ? Do we know the complete catalog number that your parts guys are sending? Could they be off by that one digit ?

Did you ever watch the contacts while slowly depressing the solenoid button to see whether they're Break before Make or Make before Break ?
bowling14A.jpg
 
  • #261
153
7
spec sheet didnt even mention overlap that i could find

that snip i put up showing "overlap" contacts versus "standard" came out of a selection guide that for some reason isn't in the technical bulletin / specs we've been studying . I guess they figure a contact is a contact and it's some other part that controls whether it overlaps another contact.

<Rant>Very frustrating. I never heard them called that before, i'm used to "Break before Make" not "Standard" and "Make before Break" not "Overlap".
I think motorcycle gear shifters belong on the right hand side, too. <EndRant>

Used to be when i got this confused i'd sit down with a relay and the box it came in and the purchase order for it, cross check part number versus catalog number &purchase ordwr versus what the words say about contact operation and verify that by watching the contacts move as i depress the solenoid plunger. But that was in the power plant where everything was as over-documented as military gear. As you see fr some similar relays a simple 0 or 1 buried in the catalog number changes what you get from "Break Before Make" to "Make Before Break".
Sometimes the catalog number isn't on the part because it's made from subassemblies each bearing its own part number.

Is there a picture of the relay that melts its contacts someplace in this thread with a part number on it ? Do we know the complete catalog number that your parts guys are sending? Could they be off by that one digit ?

Did you ever watch the contacts while slowly depressing the solenoid button to see whether they're Break before Make or Make before Break ?
View attachment 107104
As stated before I used two meters one on NO and one on NC watched continuity. By watching I could not tell if make before break occurred. It happens too fast. I'm using analog meters. With the new relays you can't see the contacts. I have had all makes of relays the most common are the AB 700CF.
 
  • #262
153
7
Ok
spec sheet didnt even mention overlap that i could find

that snip i put up showing "overlap" contacts versus "standard" came out of a selection guide that for some reason isn't in the technical bulletin / specs we've been studying . I guess they figure a contact is a contact and it's some other part that controls whether it overlaps another contact.

<Rant>Very frustrating. I never heard them called that before, i'm used to "Break before Make" not "Standard" and "Make before Break" not "Overlap".
I think motorcycle gear shifters belong on the right hand side, too. <EndRant>

Used to be when i got this confused i'd sit down with a relay and the box it came in and the purchase order for it, cross check part number versus catalog number &purchase ordwr versus what the words say about contact operation and verify that by watching the contacts move as i depress the solenoid plunger. But that was in the power plant where everything was as over-documented as military gear. As you see fr some similar relays a simple 0 or 1 buried in the catalog number changes what you get from "Break Before Make" to "Make Before Break".
Sometimes the catalog number isn't on the part because it's made from subassemblies each bearing its own part number.

Is there a picture of the relay that melts its contacts someplace in this thread with a part number on it ? Do we know the complete catalog number that your parts guys are sending? Could they be off by that one digit ?

Did you ever watch the contacts while slowly depressing the solenoid button to see whether they're Break before Make or Make before Break ?
View attachment 107104
Here is what I did: I mounted a Siemens 3TH4022-0A it's the only relay I have its old but OK for test. I mounted to a board then made a z bracket with a screw that will allow me to adjust it to push down on button on top of relay. What I found was NC open before NO close. There is actually a position Where it's neutral all 4 are open..
 
  • #263
jim hardy
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Here is what I did: I mounted a Siemens 3TH4022-0A it's the only relay I have its old but OK for test. I mounted to a board then made a z bracket with a screw that will allow me to adjust it to push down on button on top of relay. What I found was NC open before NO close. There is actually a position Where it's neutral all 4 are open..

Okay, thanks . That relay doesn't "overlap", it's break before ,make which they seem to call "fixed" .
Number agrees with their catalog

.
http://www.datasheet4u.com/download_new.php?id=661606
bowlingrelay2.jpg



AB700CF i can't find any mention of Make before Break. so for now i'll just hope it's not an option and one of the other ideas is what's been killing contacts..
That delay you put in sounds like the right approach to fixing a contact race.

Time will tell.



thanks again, old jim
 
  • #264
Tom.G
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The 25 amps motor start exist at the NC opening
This does not make sense. The NC contacts go to the 8 Ohm resistor and the current thru that resistor can not exceed 120V/8 Ohms = 15Amps.

As far as checking the MOV I just checked continuity.
The MOV should show open when the applied voltage is less than about 175V. If you measured it in the circuit with an ordinary Ohm-meter, you measured the motor resistance. If you measured it disconnected from the circuit, what did you use for a voltage source and a load?

Here is what I did: I mounted a Siemens 3TH4022-0A it's the only relay I have its old but OK for test. I mounted to a board then made a z bracket with a screw that will allow me to adjust it to push down on button on top of relay. What I found was NC open before NO close. There is actually a position Where it's neutral all 4 are open..
Please do that with the AB 700CF relay since that is the one that is failing. Testing a different relay tells us nothing.

Can you give us the the part No. of the relay that was ordered, and/or the number on the box, and/or the numbers on the contact block? Any and all info will be helpful. Something very strange is going on.
Well?

@jim hardy
AB700CF i can't find any mention of Make before Break. so for now i'll just hope it's not an option and one of the other ideas is what's been killing contacts..
But you did find a reference to overlapping AB contacts in your post #237.
 
  • #265
jim hardy
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But you did find a reference to overlapping AB contacts in your post #237.
i think it was 253 ?

They hide it well
http://ab.rockwellautomation.com/Relays-and-Timers/700-N-NEMA-Industrial-Relays
bowlingrelayoverlap.jpg


but i've yet to find anything like that for 700C

oops here it is
http://www.ab.com/en/epub/catalogs/12768/229240/229266/229661/3087130/229731/tab5.html
bowlingrelayoverlap700.jpg


so i think one should verify he doesn't have the 1L contact blocks on his 700CF relay .
why they call it overlap one catalog and late break. early make in another is one of those pesky little details that drive me nuts .

yes, 25 amps thru an 8 ohm resistor with 120 volts available is curious
not that it's inexplicable but it sows doubt. Are all the wires in the right place?
 

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