(The following discussion assume no load is connected to the generator.)
1. Source of Magnet is moving relative to the coil.
The strength of Magnetic field experienced by the coil is changed by B=Original Strength of Magnetic field/Distance^2
2. Thus the EMF produced at the coil= -2*Original Strength of Magnetic field*Velocity of the Magnetic relative to the coil/Distance^3
(Negative sign indicate a repulsive poles)
*3. The voltage built up at the coil experience impedance(Magnetic inertia of the core), the electrical current is building up slowly.
Higher impedance— longer reaction , Lower impedance— faster reaction
4. The electrical current from the coil magnetize the core, the core become a Magnet with polarities opposing the change of external magnetic field.
5. An opposition force is experienced by the source of Magnet.
The above discussion is simplified with only 1 Magnet moving relative to 1 coil. In practice, we have most often m Magnets with n coils. We could thought of m independent cycle overlapping with each other in each of the n coils.(Assume that n coils doesn’t interact with each other.)
Although the process is generally following the above sequence. However, since 3 often take longest time. It follow that before when a coil has completed 1 cycle, another cycle already started. So the cycles doesn’t just overlapped by source of Magnetic field, but also by the timing of each cycle.
To prevent complicated interaction and overlapping of processes. I suppose traditional generator tend to have coils of impedance closely match with the velocity of the Magnetic source. Therefore for each generator it has an optimal speed for rotor with guarantee efficiency. When the generator is operating at a speed different from its optimal speed, the efficiency maybe lowered due to mismatch of cycles.
When impedance is too high compare to the rotational speed of the Magnet, it follow that the Magnet already departed from the coil before 3-5 happen.(Or 3-5 happen to produce a retarding force against another Magnet). The rotor thus experience little or no retarding force. (Therefore we could theoretically then any Generator into overunity by rotating it fast enough)
On the other end, if the impedance is too low compare to the rotational speed of the Magnet, 3-5 may took place before Magnet is closest to the coil. Therefore also reduce the retarding force against the Magnet. And if the impedance is a match of the rotational speed of the Magnet, the retarding force is maximum.
Theoretically, we could design a Generator to rotate at certain speed which we carefully program the cycles such that the drag force is minimized. Or maybe in some case, aiding the movement of rotor instead of retarding it.
(Clever audience should notice that this train of thought is how we can arrive at an overunity Generator.)
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