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Calculating Device Power with Formula P=U*I: Router Example (Input vs Output)

rzecz12387 40607 8
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  • #1 7324661
    rzecz12387
    Level 11  
    Hello
    The power is calculated from the formula P = U * I
    For example, I have a router that is powered by 5V and 1.2A.
    On the plug it says:
    Input 100-240V 0.15A 50-60Hz LF
    Output 5V 1.2A

    To calculate the router power, I have to substitute U and I input or output in the formula?
    This is where the power of the power supply or router is calculated?

    Then I have to calculate how many kWh it takes, but I will calculate it myself.

    greetings
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    #2 7324733
    wolek14
    Level 31  
    The apparent power is taken, i.e. S = UI, i.e. in your case 230V * 0.15A = 34.5VA ...
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  • #3 7324813
    balonika3
    Level 43  
    wolek14 wrote:
    The apparent power is taken, i.e. S = UI, i.e. in your case 230V * 0.15A = 34.5VA ...
    Not. The active power is consumed, i.e. it is lower than the apparent power in this case.
  • #4 7324915
    rzecz12387
    Level 11  
    So what power is it after all?
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  • #6 7326204
    Anonymous
    Anonymous  
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    #7 7326239
    Paweł Es.
    VIP Meritorious for electroda.pl  
    The only thing you know for sure is that the device itself consumes 6W (5V * 1.2A) of active power, but you do not know the processing efficiency of this power supply, so you can not calculate how much power is consumed by the whole (router + power supply), it will definitely be more than 6W but how much more is not known. It is not known for what specific voltage value this primary current is given (perhaps for the minimum voltage or for some average value).
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  • #8 7329015
    rzecz12387
    Level 11  
    And if I knew the primary voltage, it would be possible to count the power of the whole?
  • Helpful post
    #9 7330168
    Paweł Es.
    VIP Meritorious for electroda.pl  
    You would have to know the voltage and current consumed at a specific load of this power supply, and measure them with a meter that correctly measures the RMS value of distorted waveforms (the input current here is very distorted, strongly impulse).
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Topic summary

The discussion revolves around calculating the power consumption of a router using the formula P = U * I. The user inquires whether to use input or output values for voltage (U) and current (I) in the calculation. Responses clarify that the router consumes 6W of active power (5V * 1.2A), but the total power drawn from the power supply is uncertain due to efficiency losses. It is suggested that measuring the actual power with a wattmeter is necessary for accurate assessment. Additionally, knowing the primary voltage and current at a specific load would help in determining the total power consumption more accurately.
Summary generated by the language model.
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