drseti wrote:The Rotax generator is really a cool design. (OK, I'll admit I'm a technology nerd.) They embed permanent magnets in the circumference of the flywheel. Thus, spinning magnetic field. Then, they place a total of seven stationary coils around the periphery of the flywheel housing. Since the coils are stationary, there's no need for slip rings or brushes.
The spinning magnetic field induces currents into the stationary coils. If you properly connect to a pair of coils spaced physically 180 degrees apart around the flywheel, you get a raw voltage. So, one pair of those coils generates power for one capacitive discharge ignition module. A second pair does the same for the other CDI module, and a third feeds the voltage regulator module that powers the main bus.
That leaves a single coil to produce a pulse of voltage each time the flywheel makes a revolution. And that pulse, students, drives the tachometer.
Pretty cool, no? Class dismissed.
Is this going to be on the exam?