voltsperhertz

Volts per hertz (V/Hz) is a ratio that expresses how much voltage is applied per unit of frequency. In electrical engineering, V/Hz is most commonly used to describe the control characteristic of adjustable-speed drives for alternating-current motors. In volt-per-hertz control, the drive adjusts the output voltage as the frequency changes in order to maintain approximately constant magnetic flux in the motor, which helps sustain torque and prevent core saturation.

The V/Hz value is calculated as V/f, where V is the applied voltage and f is the frequency in hertz. For example, a motor rated for 230 V at 60 Hz yields a V/Hz ratio of about 3.83 V/Hz in the linear region. Typically, a drive uses a linear V/Hz region up to a base frequency, increasing or decreasing voltage proportionally with frequency to keep flux constant. Beyond this base frequency, voltage may be held constant to avoid overvoltage and insulation limits.

In practice, manufacturers specify a V/Hz profile as part of a motor drive’s settings. Engineers use this profile to tune acceleration, deceleration, and torque delivery. While V/Hz is a simple ratio and not an SI base quantity, it provides a convenient way to characterize how voltage scales with frequency in systems designed to control motor speed.

Other uses of the term appear in signal processing or instrumentation contexts as a scaling factor between voltage and frequency, but in those applications the meaning can be less standardized than in motor control.