Country, region and language selection

International websites


Americas / Oceania

Africa and Middle East

Asia / Pacific

Frequency inverter

A frequency inverter is an electronic device that receives three-phase or alternating current and changes the output voltage in amplitude and frequency. This is then used to improve the run-up and speed behaviour of three-phase motors (also see Starting method). Frequency inverters also control the rotational speed of single-phase asynchronous motors, whereby the inverter energises the second phase previously generated by the capacitor.

Core components of the frequency inverter include a rectifier that feeds a direct-current or direct-voltage link and an inverter powered by this link. The inverter generates a voltage whose mean waveshape corresponds to the sinusoidal voltage of the required frequency and amplitude. See Fig. 1 Frequency inverter

Three-phase motors operated using a frequency inverter can infinitely vary their rotational speeds from zero up to their nominal speed without experiencing a drop in torque. Since frequency inverters produce substantial electrical interference along the motor supply cable, they must frequently be shielded (see Shielding). A sine filter between the frequency inverter and the motor can also suppress interference.



Become part of our team!

Become part of our team!

As an international employer, KSB offers exciting challenges in many different areas.

Regardless whether you are an experienced professional or a pupil, student or graduate ─ learn more about our work culture and find job openings from all over the world in our job portal.