Abstract: An alternator assembly includes: an alternator having an alternator input; a variable transmission assembly including an input pulley, an output pulley coupled to the input pulley and the alternator input, and a solenoid configured to adjust a gear ratio between the input pulley and the output pulley; a rotation speed sensor coupled with at least one of the output pulley or the alternator input and configured to output a first signal; and a controller. The controller is configured to determine the rotation speed of the alternator input based on the first signal; compare the rotation speed of the alternator input to a set rotation speed; and output an adjustment signal if the rotation speed of the alternator input differs from the set rotation speed so the solenoid adjusts the gear ratio such that the rotation speed of the alternator input is equal to the set rotation speed.