Selection of the Power Supply

Today, I'm posting about the selection of power supply. This is just a tip and calculation.

These estimated demands on the power supply, along with any additional load requirements for the particular power supply, including the minimum amount of time between surges (inrush), are used to choose the power supply. You will ask me that how to know that current, power and voltage of the electrical components. You can find it by reading instruction manual books or specification labels on the electronic components.

📝Although the majority of power supplies can operate at 100% of their rated capacity, it is advised to account for an additional 30%. However, other scholars argue that 20% should be included. What you plan to do with the gadgets in the future will determine this. This prolongs the life of the power supply and enables it to operate cooler and more efficiently.

When i searched from the internet, there are two kinds of calculation. But they are not different. There are the calculation based of Current and calculation based on Watts.

📝Here is the example of the calculation based on Watts. That calculation is from Advantech.

📌Device #1 consumes 1 Amp and needs 24 VDC [24 VDC x 1A = 24 Watts].

📌The second device draws 500mA and needs 24 VDC [24VDC x (500/1000)A = 12 Watts].

📌The needed total power is (24 + 12 Watts) times 1.3 = 46.8 Watts.

✅ 50 Watts would be the result of rounding up to the nearest 10 Watts.

Consequently, you would choose a power supply with a 50 Watt rating and a 24 VDC output.

Derating for extended operation: 50 x 120% = 60 Watts.

📝Here is the example of the calculation based on Current.

Select a 24 Vdc power supply for a control panel containing:

📌Qty (8) 7A contactors
📌Qty (4) 18A contactors
📌Qty (2) relays
📌Qty (5) indicating lights.

✅Total Surge Current = 3.47 A
✅Total nominal Current = 1.55 A

✅Derating for prolonged operation: 1.55 * 120% = 1.86 is the total nominal current.

By using those answers, you can choose the perfect type of power supply for your system.