I am trying to explain basic operation of a plain vanilla power transformer and I'm not sure I get what's going on here. I've clicked and clicked and clicked and this is what I've come up with. If anybody that understands this stuff could tell me if this is correct or not I would be greatly appreciative.
Basic principles of operation of a single phase power transformer. Assume in the initial condition that the primary is connected to a constant voltage AC source and there is nothing connected across the output of the secondary – infinite impedance. The current in the primary is being controlled by Ohm’s Law. V=IR where: V is the applied voltage, I is the resultant current and R is the impedance. The impedance of the coil is the vectoral sum of the DC Resistance of the copper and the XL – the Inductive Reactance. XL is a restriction to the flow of current that is being caused by the counter electromotive force, a force that counters the building and collapsing field surrounding the primary windings and by the counter magnetomotive force, a force that counters the building and collapsing field in the magnetic core.
The field in the core is inducing a voltage in the secondary windings. There is a voltage, but because there is no load, there is no current. Now let’s see what happens when we connect a load. Because a current is now flowing in the secondary, like the current in the primary, the current in the secondary is creating a field. According to Lenz’s Law, this field is in opposition to the field that created it, the magnetic field in the core. Because the field in the secondary is opposing the field in the core, the net counter field seen by the primary decreases. As such the inductive reactance of the primary has been lowered and so more current is flows in the primary. These fields work continuously and inseparably to maintain this balance. The net field in the core is always the same – the field that was there before any current was flowing in the secondary.
Basic principles of operation of a single phase power transformer. Assume in the initial condition that the primary is connected to a constant voltage AC source and there is nothing connected across the output of the secondary – infinite impedance. The current in the primary is being controlled by Ohm’s Law. V=IR where: V is the applied voltage, I is the resultant current and R is the impedance. The impedance of the coil is the vectoral sum of the DC Resistance of the copper and the XL – the Inductive Reactance. XL is a restriction to the flow of current that is being caused by the counter electromotive force, a force that counters the building and collapsing field surrounding the primary windings and by the counter magnetomotive force, a force that counters the building and collapsing field in the magnetic core.
The field in the core is inducing a voltage in the secondary windings. There is a voltage, but because there is no load, there is no current. Now let’s see what happens when we connect a load. Because a current is now flowing in the secondary, like the current in the primary, the current in the secondary is creating a field. According to Lenz’s Law, this field is in opposition to the field that created it, the magnetic field in the core. Because the field in the secondary is opposing the field in the core, the net counter field seen by the primary decreases. As such the inductive reactance of the primary has been lowered and so more current is flows in the primary. These fields work continuously and inseparably to maintain this balance. The net field in the core is always the same – the field that was there before any current was flowing in the secondary.