Assembly comprising an alternator and a motor coupling device, in particular vehicle motor

The assembly has an interface (5) including a speed regulator with two rotation speed reduction ratios. The speed regulator allows coupling of an alternator (4) with respective reduction ratios when an internal combustion engine (2) is provided with a rotation speed in two different ranges. The reduction ratios are determined to limit the range of rotation speed of the alternator. An independent claim is also included for a process for producing an alternator for an electromagnetic assembly.