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Sizing Power Supply in Electrical Cabinet

  1. Feb 6, 2013 #1
    What things do I need to consider when selecting a proper sized power supply? Basically this is control power, ouputs are pushbutton lights, alarm horn, and solenoid valves. Do I look at the peak inrush current? Average holding current?
  2. jcsd
  3. Feb 6, 2013 #2
    You literally may want to make a list of all of the devices being fed and add their current requirements- in our systems this exercise is part of our design requirements. Be wary of large solenoids and motors as they may have large inrush currents - as you have alluded to.
  4. Feb 6, 2013 #3
    So basically I would be adding up the total current? Then simply select a power supply with enough current capacity? If a spec sheet list inrush current in VA, what formula would I apply to find Amps(A)? This is 3-phase by the way.
    Last edited: Feb 6, 2013
  5. Feb 6, 2013 #4
    Yep, but when you said power supply I was think of a DC supply - is it DC with a 3 Phase AC source? Or describe what it is a little more.

    For DC the Amps will just be x VA / Voltage. EG 300VA and 24 V ... 12.5A....

    3 ph AC is a little more complicated - but for VA it will depend if the device is being connected as a 3 phase device or a single phase device. Single phase same as above, 3 phase √3*V* A(in one phase)
  6. Feb 6, 2013 #5
    I apologize for not being clear, well not proof reading my comments. Anyway, I need to get a 24VDC power supply, this is being fed by 120VAC. My main question was to select the 24VDC power supply as it relates to total current?
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