Relays amphere rating

Discussion in 'General Electronics Chat' started by cevval, Jul 1, 2012.

  1. cevval

    Thread Starter Member

    Dec 6, 2011
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    0
    The PCB type relays on the market are rated as follows, as an example:
    12V dc coil and the contacts are 16A at 230VAC. But I want to use the contacts at 12V loads.
    My questions is: Is it possible to use the contacts for 16A loads at 12VDC?
    How to corelate such relays in order to use them at 12VDVC loads?
    Thanks in advance.
    (Please don't fool me as stupid because of the question. I am not an electronic guy, just a hobiest trying to learn someting about electronics from internet.)
     
  2. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    Relays can be cross-applied in that manner......the thing to consider is that when relays are small, the space between "business contacts" is so tiny when in an off state, energizing them will cause arcing betwixt the load contacts, which will fry them in short order, and likely detonate, or fuse, sending current where you don't want it.
    I can never seem to remember which way the balance tips .....Gals / guys weigh in ??
     
  3. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    Lower voltage should be easier to switch all other things being equal. Beware of inductive emf in circuits with lots of L. So I think relay should be fine.
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,981
    3,221
    The contact DC voltage rating is typically less than AC rating since there is no zero crossing of the current to help break the arc when the relay contacts open. Operating at 12V with full current is probably ok if there is no significant unclamped inductance in the circuit. You might consider an automotive relay. They are designed to carry DC current.
     
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  5. cevval

    Thread Starter Member

    Dec 6, 2011
    30
    0
    First of all thanks for your helpfull explanation. The load is about 6 amp. But at the beginning of circuit, there is inductor with ferrite core and 470uFarad large capacitor for time delay operation of the circuit. Ofcourse, there is diode and a small (1.0u) capacitor over the relay coil. What do you mean by unclamped inductance. Could the a.m. parts cause unclamped inductance in the circuit. An automontive relay could be better of course, but it is difficult to find pcb type automotive relay in the market .
     
  6. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    A good source of small -- cubic inch ? 12v relays possibly capable of the amperage you mention, is your local John Deere [ or other ] lawntractor dealer.......I packratted everything that would otherwise wind up in the dumpster when I worked for one. Opened each one up, and canned those with seared contacts or smell of overheating...........They are nice for such projects !
     
  7. crutschow

    Expert

    Mar 14, 2008
    12,981
    3,221
    Unclamped inductance is any inductance in the load circuit with out a suppression diode (or other suppression circuit) across the inductance.

    What are a.m. parts? Ones that only work in the morning? ;)
     
  8. cevval

    Thread Starter Member

    Dec 6, 2011
    30
    0
    The above mentioned (a.m.) parts are: One inductor with a ferrite core and a big capacitor of 470uFarad at the beginning of circuit (power supply side). The load that is feed by the relay contacts is two incandescent lamp, 21W each.
     
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