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# Need To Know How Much Heat Your Power Supply Will Produce?

Submitted by OMRON Corporation
Do you need to figure out how much heat the power supply that you're planning on using will produce?

The first thing that you need to understand is where the heat produced comes from. The heat emanating from the power supply is the power supply's internal energy loss. The lost energy is emitted from the power supply in the form of measureable heat.

Below are equations provided by OMRON to help you calculate the amount of heat produced by a given power supply:

Equations:

Internal loss (W)

= Effective input power - Output power

= Output power/Efficiency - Output power

Note: Reducing the load rate is an effective way to reduce the amount of heat produced.

Example: Calculating the Heat Produced by a 100-W S82K Switch Mode Power Supply

Power rate: 80%

Output power: 24 V × 4.2 A = 100.8 W

Effective input power: Output power/Efficiency = 100.8 W/80% = 126 W

Internal loss (heat produced): 126 W - 100.8 W = 25.2 W

To convert the internal loss to calories:

By Joule's law, 1 W = 0.24 cal/s,

so 25.2 W = 25.2 × 0.24 cal/s = 6.05 cal/s