The present invention relates to the measuring of phase currents in an inverter, where by pulse width modulation controlled semiconductor switches invert a direct voltage from an intermediate circuit into a three-phase alternating voltage. The phase currents are measured by measuring the intermediate circuit current when an active switch state creates an unambiguous relation between the intermediate circuit current and a phase current. Time shifts in the phase current measuring can be avoided by measuring the value i.sub.d of the intermediate circuit current in two separate settings (u.sub.1, u.sub.1, u.sub.6, u.sub.6) of the same active switch state (u.sub.1, u.sub.6) in a modulation period (T.sub.sw) and by creating a resulting means value of the measured values. The mean values can be related in time to the center of the modulation period, and the third phase current at the same time can be calculated, because the sum of the phase currents is equal to zero.