What Are The Alternator Stator And Rotor?

Those magnets are really strong!

The more electronics that manufacturers put on motorcycles—ignition, fuel injection, and all the new rider aids—the need for electric power increases, so alternators have had to become more and more powerful.

In the case of our Honda CBR600RR engine, the alternator rotor is attached to the crankshaft and has magnets in a ring. The alternator stator attaches to the outside of the crankcase such that an assembly of iron poles, each with a coil of wire wound around it, fits inside the rotor.

As the crankshaft spins, magnets are constantly reversing the magnetism in each pole. Those reversals induce currents in the wire windings, which sends three-phase power out of a connector. When the rotor is spinning at 10,000 rpm, the stator pushes out some power!

Every motorcycle has an equivalent device like this. Not in every case is it mounted on the crankshaft end; sometimes it is mounted behind the engine and driven by gears. But there will be some source of alternating current power on every modern motorcycle.

In order to charge the motorcycle’s battery, that alternating current has to be rectified to direct current, which is then used through a voltage regulator to charge the battery. I like this part. It’s nice looking. Good stuff.