Transformers, its current and its resistance

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SUMMARY

This discussion centers on the operation of transformers in relation to desktop computer power supplies and their energy consumption. It establishes that a transformer connected to home AC exhibits a measurable resistance, which influences the current flow. The conversation highlights that as the power demand from the desktop increases, the power supply must draw more energy from the AC source, despite the transformer’s resistance. The role of counter electromotive force (EMF) in affecting the primary circuit's resistance is also emphasized as a key factor in understanding this dynamic.

PREREQUISITES
  • Understanding of transformer principles, specifically basic transformer operation.
  • Knowledge of electrical resistance and its measurement using multimeters.
  • Familiarity with desktop power supply functionality and energy consumption dynamics.
  • Concept of counter electromotive force (EMF) in electrical circuits.
NEXT STEPS
  • Research "Transformer basic principles" for foundational knowledge.
  • Explore "Counter EMF effects in electrical circuits" to understand its impact on power consumption.
  • Study "Desktop power supply efficiency" to learn about energy optimization techniques.
  • Investigate "Measuring electrical resistance in transformers" for practical applications.
USEFUL FOR

Electrical engineers, power supply designers, and anyone interested in understanding transformer behavior and energy consumption in electronic devices.

Taturana
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Hello,

Suppose a simple transformer, not connected to a circuit (just to the home AC). If we get a multimeter and measure its resistance we will get a number. So if we plug it into the home AC, it will consume energy (constant power).

Now suppose we have a desktop computer power supply. Well, the desktop consumption varies: if we are playing a game, the video card is dissipating more power etc. So, I would imagine that if the desktop consumption raises, the desktop is not only consuming more from the power supply, but the power supply is also consuming more from the home AC, otherwise it will be a really huge non-optimized solution for power supplies. But I also know that the only thing connected to the home AC (if we look the power supply circuit itself) is the transformer, which is, in essence, an inductor (but acts like a resistor, it's a lot of cable, it has a resistance).

Given this, the main question is: if the unique thing connected to the home AC is the coil of the transformer, and this coil has a resistance, which let's a I current flows, how could the power supply consume less or more power from the home AC?

I think you all understand my question. Please, could someone give me a clear explanation on that?

Thank you very much
 
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I can't do a detailed explanation as I don't know enough, but I believe that the different items that are consuming power in the secondary windings circuit cause various levels of resistance in the primary circuit through counter EMF.
 

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