contactor AC220v coil,to switch DC12v high current?

Discussion in 'General Electronics Chat' started by walrezk, Aug 9, 2015.

  1. walrezk

    Thread Starter New Member

    Aug 9, 2015
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    hi there
    plssss asssisssst me
    i want to install a contactor to switch on and off a DC12v coming from 1600AH battery(4 *400AH sealed lead acid )going to the inverter..that contactor to be controlled by AC220v grid power...which type of contactor could it be,how to purchase it.pls look at my diagram c.jpg
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    12,914
    3,548
    A contactor used in HVAC/Plasma machines etc should be suitable, know as Special Purpose, this has contacts that are frequent-switching rated and usually have arc chutes etc.
    What is the anticipated switching current?
    Max.
     
  3. walrezk

    Thread Starter New Member

    Aug 9, 2015
    5
    0
    hi
    the batteries current is 1600AH
    if that what u mean by ur question ..pls check my drawing
    i appreciate ur assisstance
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    5,063
    1,099
    Thats total capacity..
    What is the maximum anticipated current draw (this would be based on the loads attached to it)
     
  5. walrezk

    Thread Starter New Member

    Aug 9, 2015
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    HAMMM..the batteries are connected to a 3000w inverter..if that u mean
     
  6. walrezk

    Thread Starter New Member

    Aug 9, 2015
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    ok fine...i tried to do a manual switch instead of the contactor using 100A MCB,it was really heating,,so i need a contactor stronger than that
    thanx
     
  7. tcmtech

    Distinguished Member

    Nov 4, 2013
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    Guessing that your 3000 watt inverter is like my better ones that have a 6000 watt surge capacity at a nominal 12 volt input it would be drawing about 300 amps with conversion losses factored in. 600 if it has a high surge capacity and get taken to it's maximum peak capacity.

    Now that said yes most AC rated contactors will handle 12 volt DC just fine but you still have to obey their amp ratings and respective wire/cabling sizing requirements.

    So for the total amp capacity you are planing to carry which in your case for a 3000 watt inverter that could conceivably draw up to 300 amps for extended periods you would need a contactor that can carry that much as well putting your minimum sizing at a 100 amp three phase unit.

    Personally if it was me for the costs involved I would just use a common step down transformer to drive a large low voltage high current continuous duty rated solenoid to do the DC switching.

    Either that or simply wire up a 230 VAC powered relay to switch the inverters main power switch on and off via a remote input assuming it has one like most higher powered units do.
     
  8. walrezk

    Thread Starter New Member

    Aug 9, 2015
    5
    0
    yes..my inverter as u said
    since u offered other ideas,let me tell u why im doing such a horrible connection
    im trying to install a high current 12v battery charger of 2600A current,so i can manage to charge that 1600AH battery in shorter time(knowing that grid power only stay in Lusaka for 14h daily only),so im using this contactor to disconnect the battery and that giant charger from the inverter when grid power is on(i.e.while charging) otherwise the alarm of the inverter will scream cos of overcharge.i want a complete self charging/inverter connection,fully automated.
     
  9. tcmtech

    Distinguished Member

    Nov 4, 2013
    2,686
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    Unless you are force charging your batteries at more than ~15 volts the inverter shouldn't be having problems with setting off input over voltage alarms.

    Now relating to charging a 1600 AH battery bank personally I have no problem with letting big batteries take all the current they want initially just so long as the peak charging voltage stays under 14.5 volts in a 12 volt system.

    If I was designing the system I would be setting it up with a charging system that can bring the batteries up from 10% charge to full in about 6 - 8 hours which for a 1600 AH battery bank I would be using a 400 amp charging system being it would be able to give you a full recharge in under 8 hours without doing damage to your batteries.

    Personally if it was me I would have set up the system designed around a much higher battery voltage and a commercial inverter/charger unit that ran on something like 24 or 48 volts.

    It would have saved you a lot of problems and likely money in this sort of application especially being you need to have a high output power capacity for an extended period of time with a reasonable recharge time all done automatically.
     
    nsaspook likes this.
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