Frequency converters Control Techniques

The VFD power rating should equal or exceed the motor nameplate power. For pumps and fans (variable torque), select based on the motor rating. For conveyors, cranes, and crushers (constant torque or heavy starting), choose one power step above — for example, for a 4 kW conveyor motor, we recommend a 5.5 kW VFD. Also verify that the motor's rated current does not exceed the VFD's current rating.

Yes, you need a VFD with single-phase 220V input and three-phase 380V output, such as the Veichi AC70E or AC10 T/S2 variant. Power is limited to 2.2–4 kW depending on the series. The VFD not only starts the motor but also provides soft starting, speed control, and overload protection.

Scalar control (V/f) maintains a constant voltage-to-frequency ratio — a simple, reliable method for pumps, fans, and compressors. Vector control (SVC, FOC) calculates motor current and flux vectors in real time, delivering 150–200% rated torque at low frequencies. Vector control is essential for conveyors, elevators, extruders, cranes, and CNC machine tools.

An EMC (electromagnetic compatibility) filter reduces high-frequency interference that the VFD generates in the power supply and airwaves. It is mandatory for facilities with sensitive equipment (medical, laboratories, server rooms), residential buildings, and when the cable between VFD and motor exceeds 25 m. The Veichi AC10, Delta VFD-E, and INVT GD20 models include a built-in Class C3 EMC filter.

On pumps and fans, savings range from 20% to 60% depending on the load profile. Power is proportional to the cube of speed (P∝n³): reducing speed by 20% halves energy consumption. If equipment typically operates at 70–80% of rated speed, average savings are approximately 40%. Payback period for a VFD on a pumping station is 6 to 18 months.