RPM and Hertz

There are 36 spokes in the wheel and 36 magnets. As the magnets pass the coils of wire they will produce a sinusoidal wave of induced current. If the wheel revolves once every second then there will be 18 cycles of induced current in the wires. The frequency of induced current would then be 18 Hertz. The voltage will depend on the number of turns in the wire, the velocity of the magnets relative to the coils and the efficiency of the inductive coupling. There are three phases each offset by 1/3 of a cycle. Here is a circuit model for this kind of generator charging a 12 volt battery.