I thought the magnitude of the induced EMF in the secondary coil was equal to the change rate of the flux linkage through that coil, and the induced EMF would produce a current which in turn produced a magnetic flux to oppose the flux that caused the current in the secondary coil.The downward flux through the core induces a positive current in the secondary winding (right hand rule again), ie the same current direction as the primary winding.
Hello, MrAl
I'm glad you mentioned the physical sonstruction and winding of the coils.
I thought the magnitude of the induced EMF in the secondary coil was equal to the change rate of the flux linkage through that coil, and the induced EMF would produce a current which in turn produced a magnetic flux to oppose the flux that caused the current in the secondary coil.
If the current i1 were positive increasing as shown in fig1 below, the magnetic flux would be also increasing and downward. At this moment, a induced voltage would be produced in coil 2 and hence the induced current i2 with their polarities as shown in fig1. But I DO NOT know whether this current i2 would be increasing or decreasing, and once there was a varied current i2 in coil 2, this i2 itself would produce a self-induced EMF in addition to the previous mutual-induced EMF, and I don't know which one would dominate. That's where I have stuck.
If the transformer in fig1 below represents an ideal one. For the choice of the voltage and current reference directions, do the following equations hold for this ideal transformer?In an ideal transformer there is no self-induced EMF in the secondary, its EMF is determined by the primary EMF and the turns ratio.
You are confusing cause and effect. The current in the secondary varies with time due to the flux generated by the primary, which generates the secondary voltage. There is no self-induced EMF.........................
Besides, if the current i2 in the secondary coil is varied with time, won't there be self-induced EMF produced in the coil?
You are confusing cause and effect. The current in the secondary varies with time due to the flux generated by the primary, which generates the secondary voltage. There is no self-induced EMF.
Hello Heidi,
I cant figure out why you would want to draw your transformers with two separate *cores*. A transformer has one core and at least two *windings*.
Two separate cores are only weakly interacting and the orientation is not clear. So draw both coils on the same core so we can see what the polarities should be.
If the core is a toroid then draw two circles to represent the core. Or you could just draw two squares. If the windings are on the center leg of an EI type core, then you can get away with just drawing a single core if you like. But this is important for determining the direction of the flux in both windings.
That's a misleading statement. The secondary coil current does generate magnetic flux in the core but, since the current direction is opposite the primary current direction, the flux is also in the opposite direction and subtracts from the magnetizing flux generated by the primary. Thus the primary current has to increase to maintain the same core flux level. That is how an increase in secondary current causes an increase in primary current...............................................
But this article says something I don't understand. Can this article represent what you are trying to explain to me, especially it says "At first, one might expect this secondary coil current to cause additional magnetic flux in the core. In fact, it does not. If more flux were induced in the core, it would cause more voltage to be induced voltage in the primary coil (remember that e = dΦ/dt). This cannot happen, because..."?
Hello, crutschowThe secondary coil current does generate magnetic flux in the core but, since the current direction is opposite the primary current direction, the flux is also in the opposite direction and subtracts from the magnetizing flux generated by the primary. Thus the primary current has to increase to maintain the same core flux level. That is how an increase in secondary current causes an increase in primary current.
You rather have the polarity backwards.I have another idea. Can I say that this is how an increase in secondary current in the negative current reference direction (referring to the secondary current reference direction in the figure attached) causes an increase in primary voltage, and that increase in primary voltage is to provide extra energy to overcome the production of the self-induced EMF, which is due to the increase of the secondary current in the negative current reference direction in the secondary coil?
Oops, there might be a contradiction. The primary voltage is a voltage source, it seems that it cannot be 'changed'. Hmmmm....
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?