Understanding Relay Spec's.

[amdx]

---
You obviously either misread me or you're just trying to be combative.

The point is that, if there were no bounce, the only stress the
contacts would experience would be the momentarily increased I²R
losses at startup; no big deal.

However, since the current is so much higher during startup, bounce
will result in a plasma capable of doing much more damage to the
contacts than the one created when breaking a resistive load.

Ok, my new relay has two sets of contacts, If I parallel the two sets,
am I doubling the chance that a set of contacts will weld themselves
together?

Is it less than a doubling?

Is it paralleling the contacts a good idea to increase MTBF?

Someone suggested a snubber across the contacts, seems to me it was big
enough to help, it would allow "quite" a current to flow in the motor.

Mikek

"quite" a word to use when you don't have a clue.

 

[TheGlimmerMan]

Someone suggested a snubber across the contacts, seems to me it was big
enough to help, it would allow "quite" a current to flow in the motor.

On a relay, one places a 'snubber' on the relay mechanical actuator
coil to clamp the back EMF spike when power is removed from a DC
energized coil. It has nothing to do with the switched contacts or
circuitry thereof.

 

[amdx]

On a relay, one places a 'snubber' on the relay mechanical actuator
coil to clamp the back EMF spike when power is removed from a DC
energized coil.

What you say is true.

It has nothing to do with the switched contacts or circuitry thereof.

I don't see any reason you can't put a snubber across the contacts
of a relay driving an inductive load.
Especially when your using DC on the contacts.
Mikek

 

[amdx]

Drat, I have to do my own homework !! Ok, I printed it out, it
will be a good read while I'm selling shrimp tomorrow.
More specifically, when I'm not selling shrimp.

Tyco has another pdf on picking relay snubber components and values.
http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3311.pdf

 

[ehsjr]

With AC, the current goes to zero every half cycle, so it generally
doesn't sustain an arc for long.

John

You seem to be implying that arcs across relay contacts with
durations of less than ~8.3 mS _don't_ stress the contacts,
or perhaps you think that stress is negligible?
What am I missing?

Ed

 

[[email protected]]

Drat, I have to do my own homework !! Ok, I printed it out, it
will be a good read while I'm selling shrimp tomorrow.
More specifically, when I'm not selling shrimp.

How's the beach business (hotels, condos, etc.) down there this year? We're
thinking of going down there for a week in September.

 

[TheGlimmerMan]

What you say is true.



I don't see any reason you can't put a snubber across the contacts
of a relay driving an inductive load.
Especially when your using DC on the contacts.
Mikek

When the contacts close, the snubber does nothing.

What does such a snubber do as the contacts bounce?

 

[Chieftain of the Carpet Crawlers]

Breakers for the big fractional-megavolt DC interties must be tricky.

John

You break the AC feeding the rectification facility, then break zero
volt pathways.

 

[amdx]

How's the beach business (hotels, condos, etc.) down there this year?
We're
thinking of going down there for a week in September.

I'm not seeing a big pickup in my business, so from my prospective things
are not
picking up. I did hear the Panama City Beach tourist development council
say that reservations are
up so we should have a good summer. The sad part; they always say that.
We never had any oil down here but the media reports really put a hammer on
tourism last year. One report I heard said they picked something like 4000
tar balls,
it amounted to 8 lbs.
Come on down, we do have the worlds most beautiful beaches and even if
tourist
traffic is down their will still be more bikini clad girls than you need to
look at.
Mikek

 

[[email protected]]

Not sure if we're going to your neck of the woods or maybe Destin (ideas?) but
I probably should make some reservations soon. We went to Orange Beach, AL a
couple of years ago. It was OK, but we'd like to try somewhere else.

Well, according to SWMBO, one is more than I need to look at. ;-)

Bikinis? It's 55F here right now. When we see a good-looking woman,
we're more likely to say "wow, she looks great in a parka."

It was in the mid-90s here this week but still rather nice. I did have to
turn the AC on for a couple of days but the forecast is for low 80's tomorrow
and sliding back into the 70s by the end of the weekend. Nice. ...for a
couple of weeks, maybe. We do need some rain, before my water bill goes
through the roof.

 

[John KD5YI]

When the contacts close, the snubber does nothing.

What does such a snubber do as the contacts bounce?

If you have to ask, you can't help. Go away.

 

[TheGlimmerMan]

If you have to ask, you can't help. Go away.

I wasn't asking, idiot. I was testing the person I was having a
discussion with, so **** off and die dumbfuck.

 

[John KD5YI]

I wasn't asking, idiot. I was testing the person I was having a
discussion with, so **** off and die dumbfuck.

I will if you will. You go first, DimWit.

 

[TheGlimmerMan]

I will if you will. You go first, DimWit.

You shame hams everywhere, as it is quite obvious that you are an
immature little bastard.

 

[Phil Allison]

"John Fields"
John Larkin

---
Geez, Crydom:

http://www.crydom.com/en/index.shtml

Opto22:

http://www.opto22.com/site/solidstaterelays.aspx

Teledyne Relays:

http://www.teledynerelays.com/industrialcommercial.asp

et al:

http://www.google.com/search?q=soli...-US&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1

are sure going to be sorry to hear that.

** Shame the app notes recommend a * 25 amp rated * SSR be used with a 1/3
HP ( 120VAC) single phase motor.

If the incandescent load is a * single * high powered lamp - similar
LARGE de-rating factors apply.



..... Phil

 

[amdx]

"John Larkin" wrote in message

I'm not seeing a big pickup in my business, so from my prospective things
are not
picking up. I did hear the Panama City Beach tourist development council
say that reservations are
up so we should have a good summer. The sad part; they always say that.
We never had any oil down here but the media reports really put a hammer
on
tourism last year. One report I heard said they picked something like 4000
tar balls,
it amounted to 8 lbs.
Come on down, we do have the worlds most beautiful beaches and even if
tourist
traffic is down their will still be more bikini clad girls than you need to
look at.
Mikek

Bikinis? It's 55F here right now. When we see a good-looking woman,
we're more likely to say "wow, she looks great in a parka."

John
At 10:30 am it's 81* today, but that doesn't matter, the shapely college
girls,
wear bikinis even when the temp is in the high 60s*. They don't want to
waste
their time at the beach.
Mikek, PCB ambassador

 

[amdx]

"TheGlimmerMan" wrote in message

What you say is true.



I don't see any reason you can't put a snubber across the contacts
of a relay driving an inductive load.
Especially when your using DC on the contacts.
Mikek

When the contacts close, the snubber does nothing.

What does such a snubber do as the contacts bounce?

It provides an alternate path for current from an inductive load
suppressing a
contact damaging arc.
Mike

 

[amdx]

"John Fields" wrote in message

Ok, my new relay has two sets of contacts, If I parallel the two sets,
am I doubling the chance that a set of contacts will weld themselves
together?

Is it less than a doubling?

Is it paralleling the contacts a good idea to increase MTBF?

Someone suggested a snubber across the contacts, seems to me it was big
enough to help, it would allow "quite" a current to flow in the motor.

Mikek

"quite" a word to use when you don't have a clue.

---
http://relays.tycoelectronics.com/appnotes/app_pdfs/13c3236.pdf
JF


Ok, read over the app note, I want pick a contact arc suppression RC.
On the third page under Capacitor Selection the author seems to arbitrarily
pick
15 volts 1 usec. as a "Contact Voltage" for his relay. I don't see where
this
15 volts 1 usec came from.
I'm using this relay;
http://www.skycraftsurplus.com/120vacdpst30amp.aspx
What would be an approximate "Contact Voltage" to work with?
For the calculations can I treat my 1 hp motor as an R of 120v / 7a = 17
ohms.
hmm...
The more I think about this, the less I think the author had any thoughts
about
inductive motor loads.
Mikek

 

[Phil Allison]

"John Larkin"

What's really tricky is using an SSR or a triac to switch the primary
of a power transformer in a rectifier-capacitor power supply.

** That can be is rather simple and is used in a few professional audio
power amplifiers of up to 500W per channel rating.

I am not referring to so called " soft start " circuits where a resistance
limits the magnitude of any inrush surge, but to simply using a hefty triac
as the AC power on-of control and a normal switch to operate the triac. The
switch is wired in series with a resistor ( say 68-100 ohms) from G1 to
gate.

The worst case inrush surge is still within the rating of a low cost 40 amp
plastic triac ( eg BTA41-600) and the normal running current such that only
a small heatsink is ever needed.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-2431-5-ND


..... Phil

 

[UltimatePatriot]

Geez, your very first post to this thread was wrong, stunningly wrong,

You are full of shit... completely full of shit.

In fact, I think that you are some sub-human shittard species.

You are shit. You are full of yourself. You emit a foul stench.

What more does one need to say about John Larkin? You are full of
yourself, and what yourself is comprised of is pure refuse.

Grow the **** up, asswipe.