Versa VFDs with low harmonics
Versa Drives can supply drives with Power Factor Control (PFC) front end for applications that require strict adherence to European Union norms (EN 61000-3-2) for domestic use.
These drives can operate from universal power supply of 110/220V single phase. An offline equipment such as a VFD which employs a rectifier-capacitor front end draws current in narrow pulses (bottom left figure) at the peak of the input voltage waveform. This results in the equipment having a low power factor, and correspondingly high harmonic currents which do not do any useful work. The low power factor results in high rms line current and the mains supply is not fully utilized.
Active PFC with boost topology is compact and corrects the power factor to near unity. Versa VFDs with active boost PFC front end have several advantages.
- Harmonics are reduced to negligible levels and EN 61000-3-2 specs are met
- A single drive + motor combination can work universally as the boost topology permits the drive to work with 90Vac – 260Vac range
- Power factor is corrected to near unity and as a result the mains supply can be utilized to its full rating
The figures shown here were taken from the different models of Versa VFDs. On the left are for a drive without PFC and the figures on the right for a drive with PFC. Note the near vanishing of harmonics and the smooth current wave shape in the drive with PFC front end.
In the picture is an open frame drive that has PFC with Class-B filter for meeting strigent EMI/EMC norms.