the invention is based on a method for detecting slip in the driving of generator or starter - generator systems . the alternators of these systems are equipped with electronic control components such as pulse - width - modulated inverters or rectifier bridges . the drive torque of the alternator is transferred to this by means of a belt drive of an internal combustion engine . when slip is detected in a comparison step , to which speed - dependent input variables are forwarded , the maximum transferrable drive torque is determined in a torque limiting step , and a closed - loop control adjusts the generator output power to said maximum transferrable drive torque .