Multiple loads

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Discussion in 'General Electronics Chat' started by Benbonell, May 10, 2013.

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  1. May 10, 2013 #1
    Benbonell

    Thread Starter New Member

    May 10, 2013
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    Hi,

    This may seem a daft question but I have 3x 24 vdc pumps that all require new power supply's.

    Each one draws 24w at max chat, could I use a 70w 24v dc power supply to run all 3? Or what could I use instead.
     
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  2. May 10, 2013 #2
    MrChips

    Moderator

    Oct 2, 2009
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    Yes, using one 70W 24V supply is ok.
     
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  3. May 10, 2013 #3
    #12

    Expert

    Nov 30, 2010
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    Umm...almost. 3 X 24 = 72 watts.
    If the pumps only occasionally use the whole 24 watts each, you might get away with it.
     
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  4. May 10, 2013 #4
    MrChips

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    My guess would be that they only draw the max 24W on startup.
     
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  5. May 10, 2013 #5
    #12

    Expert

    Nov 30, 2010
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    Good point. It would only be a problem if they all started at the same time.
     
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  6. May 11, 2013 #6
    Benbonell

    Thread Starter New Member

    May 10, 2013
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    How much of a problem? They are water circulation pumps but they are variable. They don't really get to 100 percent very often. Would it mean they just run lite?
     
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  7. May 11, 2013 #7
    MrChips

    Moderator

    Oct 2, 2009
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    We are only talking about all pumps starting up simultaneously.

    If you had three pumps connected to the same power supply and the power was turned on with all pumps on, if the power supply is unable to supply the full current then the voltage will sag. The pumps may drag a bit while starting up or may fail to start.

    Once all pumps are up and running the current required will be lower and should not be a problem as long as the power supply is properly rated.
     
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  8. May 11, 2013 #8
    #12

    Expert

    Nov 30, 2010
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    These being DC pumps, if you want to start them all at once and they won't, a nice, fat capacitor might fix it by supplying a bit of starting power. Let's play with the math. Three amps, half a second, 1 volt of loss...that's 1.5 farads. That's a huge capacitor. Better to not start them all at once.
     
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