V/Hz Drive Operating Point Calculator

A scalar (V/Hz) drive keeps the voltage-to-frequency ratio constant below the motor's rated (base) frequency, which keeps air-gap flux roughly constant and therefore keeps full rated torque available across that entire speed range — the constant-torque region. Above base frequency, the drive can't increase voltage past its rated value, so the V/Hz ratio falls as commanded frequency rises. Flux drops proportionally, and available torque falls off approximately as the ratio of base frequency to commanded frequency — the field-weakening (constant-power) region.

This calculator takes the drive's rated voltage and frequency, the frequency you're commanding, and the motor's number of poles, and reports which region the operating point falls in, the actual V/Hz ratio and commanded voltage the drive will produce, the resulting synchronous speed, and an estimate of torque capability relative to rated. It's a quick way to check whether a process that needs high torque at high speed — extruders and some pump/fan curves being common examples — is being asked to run in a region where the motor physically can't deliver full torque.

This is the standard first-order V/Hz approximation used for sizing and process feasibility checks. It doesn't model IR-compensation (voltage boost at low frequency to overcome stator resistance drop, which real drives add automatically), doesn't account for a drive's actual current limit interacting with the field-weakening torque curve, and doesn't apply to vector (FOC) or sensorless-vector control modes, which regulate flux and torque more directly than a simple V/Hz ratio.