Relay contact rating

I have a relay whse contact rating is specified as follows

Power : 460VA / 48Watts Current : 2A @ 24V DC or 230V AC

If I am not wrong, 460VA is from 230V AC * 2A. If my applications is required to switch 16V AC max with 5A max current (i.e 80VA), Can I use this relay? or max current is 2A only irrespective of voltage and AC or DC.

Load is inductive (4 ohm loud speaker) if this matters.

Thanks

-Sridhar

Reply to
sridhar09.cherukuri
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to switch 16V AC max with 5A max current (i.e 80VA), Can I use this relay? or max current is 2A only irrespective of voltage and AC or DC.

5A is too much for 2A contacts.

But. If this is for audio as you imply, then would you ever really see this current for any significant length of time?

Phil Allison will know.

Cheers

--
Syd
Reply to
Syd Rumpo

required to switch 16V AC max with 5A max current (i.e 80VA), Can I use this relay? or max current is 2A only irrespective of voltage and AC or DC.

Yes..it is for Audio and peak current will only be for short bursts.

Reply to
sridhar09.cherukuri

Yes. Never exceed the current rating regardless of the Watts (same as VA on DC, VA times Power Factor on AC).

Reply to
dave

required to switch 16V AC max with 5A max current (i.e 80VA), Can I use this relay? or max current is 2A only irrespective of voltage and AC or DC.

In my opinion, it'll be fine as long as there's no safety hazard in the event of the relay contacts not opening, but I wouldn't do it commercially. It's outside the specification of the relay so there's no comeback if someone dies in a raging inferno.

Cheers

--
Syd
Reply to
Syd Rumpo

** For domestic hi-fi use, it should be fine.

Switching will very rarely be simultaneous with the full 16 volts and 5 mps - plus with audio signals, arcing upon opening is much less than with

50/60Hz power or DC. Reason being that a low zero voltage will occur in less than 10mS and stop any arc.

The average current passed by the contacts with audio program is gonna be well less than 2 amps.

Have you ever seen the puny pushbutton switches used in most hi-fi amps for speaker switching?

.... Phil

Reply to
Phil Allison

"Syd Rumpo"

** You a fan ?

... Phil :-)

Reply to
Phil Allison

snipped-for-privacy@gmail.com schrieb:

to switch 16V AC max with 5A max current (i.e 80VA), Can I use this relay? or max current is 2A only irrespective of voltage and AC or DC.

Hello,

if you switch DC, the maximum current is 2 A and the maximum voltage is

24 V, you may switch 2 A and 16 V also, but not 3 A and 16 V.

Bye

Reply to
Uwe Hercksen

required to switch 16V AC max with 5A max current (i.e 80VA), Can I use this relay? or max current is 2A only irrespective of voltage and AC or DC.

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The 2A rating is based on the maximum allowed contact temperature 
increase with 2A into a load, either continuous DC or continuous AC, 
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Reply to
John Fields

"John Fields"

** Horse shit.

The 2A figure is the relay's rated switching capacity under at max conditions with a stated number of cycles.

When closed, the contacts can handle far more.

** The arc has to quench itself as the gap between contacts increases so 2A and 24VDC are the max conditions where this happens reliably over a large number of operations.

Relays and small toggle switches are lousy at switching DC of any size.

The use of speaker relays in audio amps is a non trivial subject with which I am very familiar.

And you are not.

.... Phil

Reply to
Phil Allison

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I disagree, since the "far more" number isn't included in any relay 
spec's I've ever seen and, since ohmic contacts generally have a 
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Reply to
John Fields

But Phil is all mouth >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

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That's just mean, and uncalled for.
Reply to
John Fields

If horses didn't shit, they would be almost as big of an ass as you are.

Reply to
Michael A. Terrell

Usually called "carry current" or "carrying current" ratings.

Relay makers don't seem to be very bold in such ratings- sometimes they are just the same as the switching ratings.

I had an old Motorola app note that claimed some "well designed" 5A relays could carry 50A.

These days, they'd cr*p on the engineers for wasting so much valuable material rather than call the product well designed.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward" 
speff@interlog.com             Info for manufacturers: http://www.trexon.com 
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Reply to
Spehro Pefhany

"Spehro Pefhany" "Phil Allison"

** OK - that is the term I was searching for.
** Must have big contacts with lotsa pressure.

... Phil

Reply to
Phil Allison

HORSESHIT!

Such materials have those characteristics, but nobody uses such materials these days, and therefore sees no such resistive media build-ups.

Common MODERN contact media is typically Platinum. You probably read your spec sheet 50 years ago. That was how long ago it applied. Hell, the PINBALL industry cleared all that hash up. Where the f*ck were you? Contacts on reed type switching assemblies, which nearly all are some form of, have been low or NO oxide materials for decades. Even an enclosed switch has little short 'reeds' with contact heads on the ends.

Platinum exhibits exactly ZERO oxidation, even after 100 YEARS of exposure. The only way to coat it with anything is to have super moist, particle laden air.

Both it AND Gold are the best metals at NOT EVER getting ANY 'tarnish' on them. Especially Platinum. Look at the valence shell!

Imbalances can cause contacts with momentary HV pulses involved to migrate surface molecules from one contact and meld them onto the other, thereby causing degradation.

Reply to
SoothSayer

It's also sometimes called thermal contact rating, which may also be expressed as a duty cycle. There is also the I^2t rating which is used for fuse selection.

Ratings such as this are usually shown for power contactors and motor starter relays. They are rated for a certain HP and locked rotor current. We use contactors for switching transformer taps and setting series and parallel connection, under "dry" conditions with essentially zero current and voltage (other than leakage through an SCR snubber).

Here is a rather extensive glossary and explanation of relay terms:

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Don't see platinum in any of the contact materials. Gold (mostly flashed and plated for low level signals), of course, and silver alloys with palladium and ruthenium.

Here is an extensive study of relay contacts, and platinum is only mentioned once regarding plating them with gold.

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ler_Holm2008.pdf

More information:

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a-Tables.html
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(4.3 MB)

Paul

Reply to
P E Schoen

ends.

moist,

'tarnish'

other,

Platinum contacts were used some 90 years ago and some problems were found:

formatting link
(13 MB)

Paul

Reply to
P E Schoen

required to switch 16V AC max with 5A max current (i.e 80VA), Can I use this relay? or max current is 2A only irrespective of voltage and AC or DC.

Hello, the current rating is 2 A. Use at 5A is beyond ratings, very poor life at best.

X-((

Reply to
josephkk

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