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I have researched about it and found the laws everywhere as if lawyers have written those answer. I know the law of conservation of energy, but I don't want to think like a lawyer, I want to think like a scientist, and want to understand what exactly is happening in the coil, in the core of the secondary that voltage goes up but current is reduced proportionately.

My understanding is this: In a step up transformer, the primary creates magnetic fields, that field aligns all the atomic magnetic dipoles in the cores towards one direction, as a result all the magnetic dipoles of all or some atoms (depending on the magnitude of current) of the entire core starts aligning in one direction; and at secondary when the atoms align in one direction their magnetic fields (flux) cuts the wire of the coil and their magnetic fields force the electrons in the wire to move in a specific direction. When electrons start moving, the ends of the coil measures a voltage because all or most electrons move in one direction, however when electrons move in one direction they create their own magnetic fields and that magnetic fields starts realigning either the remaining atoms of the core (or the same atoms of the core if core is saturated) in the old direction, this realigning of atoms reaches the primary and reduces the impedance of primary coil eventually it draws more current, so the wattage at primary matches the wattage at secondary on load.

What I don't understand is, when the voltage at secondary is higher, the current should also be higher, but that current produces it's own magnetic field which raises secondary coil's inductance, as a result the current is stopped momentarily, we say the current is lagged, oscilloscope also shows that the current and voltage are 90 deg out of phase on load. This means the current lags but does not end, so current must be observed in coil as soon as the voltage is dropped, but that doesn't happen, and if that happens how come current exists without a voltage?

I want to understand the qualitative process, once I understand the qualitative process, I'll move on to understand the quantitative formulae.

Please don't mention laws, I don't want to think like a lawyer, a law of physics should not stop us from thinking further; I want to understand what exactly happens in core and coil when more flux cuts the coil at secondary.

Yogie
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3 Answers3

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Why does current reduce in step up transformer?

The current doesn't "reduce" in a step up transformer. The current delivered by the secondary winding of a transformer is determined by the secondary voltage divided by the secondary load impedance.

Then, for the given secondary load current, the current in the primary of an ideal (lossless) transformer can be determined by dividing the secondary current by the transformer turns ratio (ratio of the number of primary winding turns to second winding turns). For a step up transformer the turns ratio is less than one, thus the primary current will be greater than the secondary current.

Since a transformer is a passive device (not a source of energy), for an ideal transformer conservation of energy requires that the product of the primary voltage and primary current will equal the product of the secondary voltage and secondary current.

Hope this helps.

Bob D
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In a step up transformer the electrons of the secondary aquire inertia due to high magnetic fields which are created by adding up all the fields of a very large number of turns of the secondary instead of a few turns of the primary. So as they are more inert they cannot be accelerated easly as the electrons in the primary so they are constrained to lower velocities and very short paths where they oscillate back and forth in the coil producing very low current even it is caused by a very high voltage that is produced by the large number of turns. The electrons on the primary instead, are less magnetically inert so they move a longer path aquiring higher velocity which causes a higher current. So You have electrons that oscillate with different lengths of oscillation paths and different velocity peaks.

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If both current and voltage goes up we wont have conservation of energy because the output power will be more than the input power and this cannot be true.