Magnet position for maximum voltage in an ac generator (Lenz's Law) 
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The picture above shows, that the voltage of a phase is greatest, when  the magnet alligns with the coil of the phase. Why is that?
To my knowledge of lenz's law the voltage and induced current should be 0 when the magnet aligns with a coil, since there is no opposing emf generated in the coil.
 A: The smaller is the gap between coil's core and the magnet, the greater is the flux change through the coil from the same magnet displacement. Thus the EMF is the highest at this phase (Faraday's law).
Now, if you add a load to the generator (in the most extreme case, short the winding of the coil), then the induced current in the coil will produce a counter-flux that will resist the magnet's motion. This is what Lenz' law is trying to tell you.
If, on the other hand, you leave the ends of the winding open, there will be no current, and no force resisting the magnet's movement. The apparent confusion in your question is that you must have a changing current in the winding, not just the EMF, to produce the opposing magnetic field.
You can also look at the whole thing from the conservation of energy standpoint. You have an ideal generator. If you give the rotor a rotating push, nothing is going to resist its rotation as long as the generator is unloaded. As soon as you connect a light bulb to the generator, the bulb will light up, at the same time eating up the kinetic energy of the rotor and slowing it down. Thus the Lenz' law can be qualitatively understood as a facet of the energy conservation law.
