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VFD Frequency – Torque – Power Calculator
See how speed, torque and power of an electric motor change with VFD output frequency (constant-torque and constant-power regions).
Speed: — rpm
Torque: — Nm (—%)
Power: — kW
Region: —
≤ rated f: constant torque, P∝f · > rated f: constant power, T∝1/f
Constant-torque vs constant-power
Below the rated frequency a VFD keeps torque roughly constant while power falls in proportion to speed (ideal for constant-torque loads). Above rated frequency torque drops as 1/f at roughly constant power (field weakening). Variable-torque loads like pumps and fans save the most energy on a VFD. DRG Motor supplies IE3/IE4/IE5 motors from 0.55 to 355 kW.
Frequently asked questions
What happens to torque below rated frequency?
Torque stays roughly constant (constant-torque region) while power decreases in proportion to frequency/speed.
What about above rated frequency?
Power stays roughly constant and torque falls as 1/f (field-weakening / constant-power region). Check the motor and load limits.
Why do pumps and fans save energy with a VFD?
Their power follows roughly the cube of speed, so reducing speed with a VFD cuts energy use sharply compared with throttling.