- #1
Darius Troy
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Hi guys,
Non engineer here trying to understand an engineering principle. I think I must be going wrong somewhere in my thought process.
1. Faraday tells us that the EMF generated in the secondary of a transformer is equal to the change in magnetic flux divided by the change in time.
2. The magnetic flux in the transformer core is equal to the MMF divided by the Reluctance of the core. The MMF is proportional to the current flowing through the primary winding, and the number of turns of the primary.
3. The ratio of the number of turns in the primary compared to that of the secondary determines the secondary voltage with a given applied voltage at the primary.
The example of a Step Up Generator Transformer:
This Transformer is humming along happily, when it's called on for a tap change. This particular Transformer has the tap changer on the Primary side. This particular tap operation alters the turns ratio by reducing the number of turns in the primary winding. The result of this is an increase in the voltage developed in the secondary winding as predicted by the turns ratio/voltage ratio relationship.
This is where my paradox begins, as by altering the turns ratio in this fashion one has reduced the MMF developed by the primary winding: there are less turns now. This means less peak magnetic flux in the core and so less voltage able to be developed in the secondary according to Faraday... The only way the MMF and therefore flux remains stable is if the current increases through the primary windings. This isn't implausible as the overall impedance of the primary winding would be less due to less turns, but this seems perhaps too simplistic?
It seems that it's taken for granted that the turns ratio is the only factor which governs the voltage generated at the secondary. How can this be the case when by altering the amount of turns in the primary side, one is directly altering the strength of the magnetic field?
Also, adding to my confusion (not that difficult a task) is the fact that there are formulas which show that magnetic flux is inversely proportional to the number of turns in a coil (Φ = V × T / N). This seems counter-intuitive, but also seems to contradict Rowland's law of Φ = Fm / Rm.
Any comments would be greatly appreciated.
Non engineer here trying to understand an engineering principle. I think I must be going wrong somewhere in my thought process.
1. Faraday tells us that the EMF generated in the secondary of a transformer is equal to the change in magnetic flux divided by the change in time.
2. The magnetic flux in the transformer core is equal to the MMF divided by the Reluctance of the core. The MMF is proportional to the current flowing through the primary winding, and the number of turns of the primary.
3. The ratio of the number of turns in the primary compared to that of the secondary determines the secondary voltage with a given applied voltage at the primary.
The example of a Step Up Generator Transformer:
This Transformer is humming along happily, when it's called on for a tap change. This particular Transformer has the tap changer on the Primary side. This particular tap operation alters the turns ratio by reducing the number of turns in the primary winding. The result of this is an increase in the voltage developed in the secondary winding as predicted by the turns ratio/voltage ratio relationship.
This is where my paradox begins, as by altering the turns ratio in this fashion one has reduced the MMF developed by the primary winding: there are less turns now. This means less peak magnetic flux in the core and so less voltage able to be developed in the secondary according to Faraday... The only way the MMF and therefore flux remains stable is if the current increases through the primary windings. This isn't implausible as the overall impedance of the primary winding would be less due to less turns, but this seems perhaps too simplistic?
It seems that it's taken for granted that the turns ratio is the only factor which governs the voltage generated at the secondary. How can this be the case when by altering the amount of turns in the primary side, one is directly altering the strength of the magnetic field?
Also, adding to my confusion (not that difficult a task) is the fact that there are formulas which show that magnetic flux is inversely proportional to the number of turns in a coil (Φ = V × T / N). This seems counter-intuitive, but also seems to contradict Rowland's law of Φ = Fm / Rm.
Any comments would be greatly appreciated.