Since tube amplifiers use output transformers sometimes using a push-pull configuration, I would like to ask, what happens to the magnetising current, which is the current component which produces the varying flux, which in turn induces the output. This magnetising current is not in phase with the output's harmonics including the fundamental. I have always seen this as a problem, but I may not be understanding something, and that is why I am asking.
Some decades ago, I encountered small transistor amplifiers which formed part of portable radios, which used an output stage involving transformers in a push pull output stage.
Some decades ago, I encountered small transistor amplifiers which formed part of portable radios, which used an output stage involving transformers in a push pull output stage.
https://en.wikipedia.org/wiki/Transformer
(In an ideal transformer) "With a voltage source connected to the primary winding and a load connected to the secondary winding, the transformer currents flow in the indicated directions and the core magnetomotive force cancels to zero."
In other words, the magnetizing current can be neglected. The secondary voltage is in phase with the primary voltage when the secondary has a resistive load.
If there is no load on the secondary, you can remove the secondary altogether, and you get an inductance. The magnetising current lags 90° behind the voltage - but that is not a transformer.
(In an ideal transformer) "With a voltage source connected to the primary winding and a load connected to the secondary winding, the transformer currents flow in the indicated directions and the core magnetomotive force cancels to zero."
In other words, the magnetizing current can be neglected. The secondary voltage is in phase with the primary voltage when the secondary has a resistive load.
If there is no load on the secondary, you can remove the secondary altogether, and you get an inductance. The magnetising current lags 90° behind the voltage - but that is not a transformer.
The magnetising current generates a varying flux, which in turn generates a secondary voltage when one is present, and if the secondary voltage is loaded and has to deliver a current, it generates its own flux, which opposes the source flux, due to Lenz's law, reflecting the loading effect on the primary.
If you search the net, you can probably find more elaborate and detailed explanations, including the relevant equations
If you search the net, you can probably find more elaborate and detailed explanations, including the relevant equations
Code:
https://en.wikipedia.org/wiki/Transformer
As Wikipedia is often vandalised, I do NOT read it. I know for sure, university lecturers penalise any student quoting wikipedia in their assignments. The reason is: it is not reliable.
I am after an answer regarding how the power tubes or transistors manage to supply a current that is not in phase with the output. The issue is at crossover with the signal itself approaching zero, while the magnetising current is at its peak.
This is NOT an easy question.
In a conventional PP, each active device operates in two quadrants, but when you take the coupling into account, the composite transformer+the pair of devices behaves as a 4-quadrant object, meaning it can source or sink current whatever the polarity of the voltage.
Sometimes, this current will be reinjected into the supply and recuperated
Sometimes, this current will be reinjected into the supply and recuperated
I don't understand the problem. Imagine a tube or transistor stage where the load is a parallel inductance and resistance. The tube or transistor is easily able to deliver currents to each, and these currents are 90° phase apart from each other.Code:https://en.wikipedia.org/wiki/Transformer
As Wikipedia is often vandalised, I do NOT read it. I know for sure, university lecturers penalise any student quoting wikipedia in their assignments. The reason is: it is not reliable.
I am after an answer regarding how the power tubes or transistors manage to supply a current that is not in phase with the output. The issue is at crossover with the signal itself approaching zero, while the magnetising current is at its peak.
This is NOT an easy question.
In real conditions the magnetizing current is very low even at the lowest audio frequency, because the inductance of the transformer is high. Not comparable to the output current (assuming a resistive load). The output devices will see a complex load, with a very large and nonlinear inductive component (hence very low and distorted magnetizing current), and a low resistive load (the ideal loudspeaker or dummy load) with a large output current. They are 90° apart, the vector sum is the current that is delivered by the output devices. Most devices tolerate a small phase difference between output voltage and current. Think about cable capacitance - same situation.
If the signal is very small, the voltage across the device (tube, transistor..) is high. Easily supplies whatever current is required.The issue is at crossover with the signal itself approaching zero, while the magnetising current is at its peak.
If that is not your question, please draw us a picture.
Wikipedia is often vandalized by children with very off-point interjections. At "best" I have seen an article about a car vandalized with a rant about the car company pricing and policy-- an unhappy customer. Once in 10+ years I fought a persistent idiot who did not understand tube radios. As for why professors don't accept Wikipedia... i worked with profs for decades and I assure you they are mostly more random and capricious than normal (non-academic) people. And Wikipedia is a special sore-point because it has potential to put them out of work.
Hysteresis?Code:https://en.wikipedia.org/wiki/Transformer
As Wikipedia is often vandalised, I do NOT read it. I know for sure, university lecturers penalise any student quoting wikipedia in their assignments. The reason is: it is not reliable.
I am after an answer regarding how the power tubes or transistors manage to supply a current that is not in phase with the output. The issue is at crossover with the signal itself approaching zero, while the magnetising current is at its peak.
This is NOT an easy question.
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