Design and mode of operation [t-head1-first]

Frequency inverters provide variable, stepless speed control of three-phase motors.

Frequency inverters convert constant mains voltage and frequency into a DC voltage, from which they generate a new three-phase supply with variable voltage and frequency for the three-phase motor. The frequency inverter draws almost only active power (p.f. ~ 1) from the supplying mains. The reactive power needed for motor operation is supplied by the DC link. This eliminates the need for p.f. correction on the mains side.

The frequency-controlled three-phase motor is today a standard component for infinitely variable speed and torque regulation, providing efficient, energy-saving power either as an individual drive or as part of an automated installation.

The possibilities for individual or plant-specific coordination are determined by the specific features of the inverters and by the modulation procedure used.