A magnetic field generator (1) of a magnetic-inductive flowmeter for generating an alternating magnetic field running at least also perpendicular to the longitudinal axis of a measuring tube, wherein at least one field coil (2), a current regulator (3), a switching bridge (4) and a microcontroller (5) all form part of the magnetic field generator (1).Two different coil voltages are provided for the coil power supply, namely an initial voltage and a lower operating voltage, and a voltage selector (6) is provided for switching from the initial voltage to the operating voltage—and vice versa.