The CS-121 and CS-130 Alternators are a complete departure from the SI series alternators that They were designed to replace. The new features include a high ampere output per pound of weight, and a totally new and different regulator. A diode trio is not used. A Delta stator, a rectifier bridge, and rotor with slip rings and brushes are electrically similar to earlier models of alternators. (Figures1 and 2)
The CS stands for Charging System, and the 121 and 130 denote the outside diameter in millimeters of the stator. By noting this number, the relative size and relative amperes output between alternators can be compared. The CS-121 and CS-130 features sealed bearings with lifetime lubrication in both end frames.
A conventional fan mounted next to the pulley pulls air through the assembly from the rear for cooling. An internal fan mounted on the rotor pulls air through the slip ring end frame to cool the rectifier bridge, regulator and rear bearing. The air is expelled through openings in the end frame. No periodic maintenance on the alternator is required.