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Releu 220v


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Buna ziua.

 

Am folosit acest tip de releu pentru a comanda intr-o aplicatie o pompa de recirculare a agentului termic cu o putere de 125w . Nu dupa mult timp a inceput sa nu mai decupleze, raman contactele alipite, trebuie sa lovesc carcasa releului pentru a decupla. Este un releu de proasta calitate sau nu este potrivit pentru aplicatia in care este folosit?

Va multumesc amticipat!

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Formatul acesta exista de multa vreme , din pacate "economia"  duce la scaderea calitatii ,contactele sunt de proasta calitate ,de aceea se lipesc la numai 125W......candva erau din platina,argint si alte aliaje facute spre a tine cat mai mult ,fata de tendinta actuala de a tine cat garantia.Ar trebui un releu de marca sau una veche de acum 30ani....

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Nov 20, 2017, 03:19 pm
You've missed that its likely to be a single-phase induction motor, so that the current is a lot higher
than if it was a resistive load due to the power factor not being unity, and that the startup current
is several times higher than the running current for these motors, and that's its an inductive load
which needs special handling.

Inductive loads typically need snubber circuits on the relay to reduce arcing at the contacts, and
need a relay rated for inductive load in the first place.

 

Hi, Nick. Don't do it. Both loads have an inductive component, and as
with all inductive loads, your problem is going to be turning it off.

A big difference between relays that are made to switch inductive loads
and those that aren't is the draw length of the contacts. Relays are
inherently "snap action", but unless you can quickly draw the relay
contacts far enough apart to extinguish the arc, you'll end up arcing
for an extended period of time. That will burn up your contacts almost
immemdiately. And this has nothing to do with the size of the
contacts, as well as very little to do with contact force (the primary
considerations in developing contact current ratings).

Another difference between the two relays is contact composition.
Inductive-rated relays do have alloy contacts which are made to better
endure the high temperatures of arcing.

Relays made to switch inductive loads do have higher current coils,
because they require more pull to draw the contact further and faster.
They're also more expensive. But they're worth it. Just as a WAG, I'd
suggest you get a relay that's rated to switch 1/4HP to be safe. For
just one ballast, I'd doubt you'd need to go with a small lighting
contactor. That probably would be overdesign. I'd also recommend a
socketed relay, so the user can swap it out if the relay doesn't live
up to expectations.

If nothing else, you can just try it. Switch your relay on and off
with a five second on/five second off cycle using a 555, and just see
how long it lasts. I would think if you can get 10,000 cycles (this
should take less than a week of testing, turning it on at the beginning
of the workday and turning it off when you leave), you can start to
have some confidence in the switching.

But I'm sure you'll find that a relay made to switch only resistive
loads is going to cause you nothing but problems in the future.

Good luck
Chris

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