Sizing Power Supply in Electrical Cabinet

[Som_P]

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?

 

[Windadct]

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.

 

[Som_P]

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.

 

[Windadct]

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)

 

[Som_P]

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?