A construction machine, in particular a road construction machine, such as a paver, comprising - a drive motor in the form of a combustion engine, - an electric load, in particular a heating coil of a heating screed of a paver for leveling the pavement material discharged by the paver, the load to be operated in an essentially constant operating voltage range, - a permanent-magnet generator which is coupled to and driven by the drive motor and which has a three-phase voltage coil package whose three-phase voltage coils (U, V, W), which are each assigned to one phase, are each divided into subcoils (U1, U2, U3; V1, V2, V3; W1, W2, W3) connected to each other and/or to their phase terminal (L1, L2, L3) via separately controllable switches (SU1-SU6; SV1-SV6; SW1-SW6), - a controller for actuating the switches (SU1-SU6; SV1-SV6; SW1-SW6), and - a detector for detecting a given operating mode of the drive motor, the detector being connected to the controller, characterized in that - the drive motor is operated in at least two operating modes having fixed operating speeds, - the respective subcoils (U1, U2, U3; V1, V2, V3; W1, W2, W3) of the three-phase voltage coils (U, V, W) have different numbers of turns, and - the switches (SU1-SU6; SV1-SV6; SW1-SW6) are actuated as a function of the operating mode of the drive motor, which is detected at an individual subcoil (U1, U2, U3; V1, V2, V3; W1, W2, W3) via the frequency thereof, in such a manner that when individual subcoils (U1, U2, U3; V1, V2, V3; W1, W2, W3) of the three-phase voltage coils (U, V, W) or groups thereof are switched on and/or off, an output voltage in the operating voltage range of the electric load is supplied to the phase conductors (L1, L2, L3) of the permanent-magnet generator. - a drive motor in the form of a combustion engine, - an electric load, in particular a heating coil of a heating screed of a paver for leveling the pavement material discharged by the paver, the load to be operated in an essentially constant operating voltage range, - a permanent-magnet generator which is coupled to and driven by the drive motor and which has a three-phase voltage coil package whose three-phase voltage coils (U, V, W), which are each assigned to one phase, are each divided into subcoils (U1, U2, U3; V1, V2, V3; W1, W2, W3) connected to each other and/or to their phase terminal (L1, L2, L3) via separately controllable switches (SU1-SU6; SV1-SV6; SW1-SW6), - a controller for actuating the switches (SU1-SU6; SV1-SV6; SW1-SW6), and - a detector for detecting a given operating mode of the drive motor, the detector being connected to the controller, characterized in that - the drive motor is operated in at least two operating modes having fixed operating speeds, - the respective subcoils (U1, U2, U3; V1, V2, V3; W1, W2, W3) of the three-phase voltage coils (U, V, W) have different numbers of turns, and - the switches (SU1-SU6; SV1-SV6; SW1-SW6) are actuated as a function of the operating mode of the drive motor, which is detected at an individual subcoil (U1, U2, U3; V1, V2, V3; W1, W2, W3) via the frequency thereof, in such a manner that when individual subcoils (U1, U2, U3; V1, V2, V3; W1, W2, W3) of the three-phase voltage coils (U, V, W) or groups thereof are switched on and/or off, an output voltage in the operating voltage range of the electric load is supplied to the phase conductors (L1, L2, L3) of the permanent-magnet generator.