I'm asking because most, if not all, explanations for eddy loss and/or hysteresis loss always refer to a.c. current.Well, why not? Of course there are losses in the core!
Thank you. My math is not great, and most tutorials are either grade-school level or graduate-level.There is still inductance, since prior to T=0 the current (i) is zero, while after the pulse has started, T>0, the applied voltage is producing some current, and thus creating magnetic flux within the core material.And since there is changing flux there would be "eddy currents", and hence losses. The math might be tedious but the theory is very straightforward.
How short? Is it dependand on size, or current, or is it a fixed constant?For most applications transformers are used for alternating current with some defined frequency range. So that is what most explanations address. My explanation is applicable for the time between T=0 and the time when the current has stopped changing. That is generally a quite short time period.
The process continues until the magnetic material can not be magnetized any more. So usually it is a very few milliseconds. At that point the current will not be changing . The time does depend on how much iron and how many turns of wire and how much resistance in the wire. We derived the equations in my physics class back in 1967. So my recollection of the math is a bit faded.How short? Is it dependand on size, or current, or is it a fixed constant?
Good point! I am with the understanding that once a transformer reaches saturation, the primary current skyrockets, with zero increase in output current. Yes/No?The losses in a solid steel core are great enough that even the cheapest transformer uses laminations. So they must be quite a bit.
The voltage in the secondary is proportional to the field strength (Tesla) created by the primary. when the core saturates the field strength cannot increase further.Good point! I am with the understanding that once a transformer reaches saturation, the primary current skyrockets, with zero increase in output current. Yes/No?
The secondary voltage is produced by the change in the magnetic field in the core. In addition, once the core saturates the transfer of energy stops, and so the impedance drops and that is why the current rises, because then the current is only limited by the resistance of the wire.The voltage in the secondary is proportional to the field strength (Tesla) created by the primary. when the core saturates the field strength cannot increase further.
Yes I should have said proportional to the change in field strength. When it stops changing at saturation there is no more there there.The secondary voltage is produced by the change in the magnetic field in the core. In addition, once the core saturates the transfer of energy stops, and so the impedance drops and that is why the current rises, because then the current is only limited by the resistance of the wire.