Help me figure out this relay?

Discussion in 'General Electronics Chat' started by XOIIO, Apr 23, 2013.

  1. XOIIO

    Thread Starter Member

    Mar 1, 2013
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    So, I salvaged 6 HASCO HAT901CSDC24-1 relays from a power supply, you can find the info about them here.

    I am having trouble figuring out what voltages these can handle. Ont he relay itself it seems to be capable of 240v AC and 14VDC, at 40 amps normally open, 30 amps normally closed, but on that site I see 500 volds DC listed?
     
    Last edited: Apr 23, 2013
  2. Gibson486

    Member

    Jul 20, 2012
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    500V is the insulation Resistance. That just tells you how high a voltage it can withstand before it starts breaking down. Your max load is 30A and 28V. That is what you should be designing with.
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Remove yourl last sentence. See TOS for explanation.
     
  4. XOIIO

    Thread Starter Member

    Mar 1, 2013
    39
    1

    Ahh, shoot.

    What is it about DC that is different than AC that makes such a difference for relays? It can handle over 200 volts AC at 40 amps but only 28 dc? Why exactly is this?

    Also, does anyone know where I could buy a DC relay that can had;e around 400 volts, and quite a lot of amps?
     
  5. panic mode

    Senior Member

    Oct 10, 2011
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    you did not provide enough info. so far it seems that you are interested in contact ratings (is that all?). you also don't say what is voltage and current you intend to use or what relay contact you need to use. in general if the contact rating is not symmetrical, it is the NO that can handle larger current.
    so using NO contact means:
    - for resistive loads (heaters, incandescent lights, etc.) this will handle up to 40A at 277VAC
    - motors 1HP at 120VAC and 2HP at 277VAC and so on....

    DC is much worse for contacts as they burn out faster than in AC circuit. When relay supports both AC and DC loads, then DC loads have lower rating. this relay has DC contact rating of respectable 30A but at voltages up to 28V. that's it. DC just chews through the contacts so if you plan on switching DC circuits using higher voltage , you must use different product. the 500V is just insulation test. this does not mean contact ratings as discussed so far, it means at this test voltage there was no noticeable leakage current, calculated resistance was greater than 10MOhm. this does NOT mean that you can run the relays in 500VDC circuits. this was just an insulation test.
     
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  6. Gibson486

    Member

    Jul 20, 2012
    199
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    DC is constant, AC is alternate. In AC, it oscillates to its max value, which is why you use the RMS value on your load calc measurements. DC, it just stays at that value.
     
  7. panic mode

    Senior Member

    Oct 10, 2011
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    in AC circuits current alternates and when it crosses zero it helps extinguish an arc formed across contact that is opening up. in DC there is no such thing so arc continues to burn until gap is too large to maintain arc or something external turns it off. this means that relay like this would turn on once, life would be good until you try to turn it off, then the arc does not extinguish, current keeps on flowing and relay is ruined.

    for DC circuits you need DC rated components and you do need to know upfront, voltage, current, etc.
     
  8. XOIIO

    Thread Starter Member

    Mar 1, 2013
    39
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    Yes what I am looking for in the end is a relay that is triggered by DC, somewhere around 12 volts possibly, that can switch 250v DC. I'm not sure what amperage it will be, but it will probably be a fair bit. I just haven't been able to find a place online that has a relay capable of this.
     
  9. panic mode

    Senior Member

    Oct 10, 2011
    1,320
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    for coil gun you would want something with low on-resistance and fast switching time. mechanical contacts are not fast and they bounce. also 20mOhm is not exactly a screamer. try mosfet with <2mOhm on resistance or for large voltage consider IGBTs or even SCRs
     
  10. XOIIO

    Thread Starter Member

    Mar 1, 2013
    39
    1

    Well it's not just that kind of project I need these for, I also want to make a pulse magnetizer for my various tools. Hopefully they make a MOSTFET or IGBT that can handle a fair bit of current, and of course I'll have to figure out how to use one of those for switching instead.
     
  11. XOIIO

    Thread Starter Member

    Mar 1, 2013
    39
    1
    Oh hey actually, I just organized my scrap parts and I do have a couple 500 volts MOSFETS, that handle 20 amps, not sure if they are AC or DC (or if there is a difference).

    Can someone provide a schematic as to how I would wire it up to trigger it with a switch or something similar? I'll give it a test when I get back from work.
     
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