Voltage to Hz Converter

Volts to Hz Calculator

Convert voltage to frequency using V/F ratio for VFDs, motor drives, and voltage-to-frequency converters.

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Key Point: Voltage and frequency are related through the V/F (Volts per Hertz) ratio in motor drives. The formula is: Hz = V ÷ (V/F ratio). Standard V/F ratios are 4 V/Hz for 60Hz systems and 4.6 V/Hz for 50Hz systems.
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Voltage to Hz converter
Table of Contents

How to Convert Volts to Hertz Using V/F Ratio

Volts (V) and Hertz (Hz) are fundamentally different electrical quantities—voltage measures electrical potential, while frequency measures how many times an AC waveform cycles per second. You cannot directly convert between them because they describe different physical properties.

However, in Variable Frequency Drives (VFDs), motor controllers, and voltage-to-frequency (V/F) converters, these quantities are linked through the V/F ratio. This ratio determines how voltage should change as frequency changes to maintain optimal motor performance.

The V/F Ratio Formula

Hz = V ÷ (V/F ratio)
Hz = Frequency (Hertz) V = Voltage (Volts) V/F ratio = Volts per Hertz

This formula is used in AC motor control to calculate the operating frequency when you know the applied voltage and the V/F ratio setting. The V/F ratio maintains proper motor flux and prevents overheating.

V/F Ratio in Motor Drives

According to Wikipedia’s article on Variable Frequency Drives, VFDs control motor speed by varying both voltage and frequency simultaneously. The V/F ratio determines how these are proportionally adjusted.

For a 240V motor designed for 60Hz operation: V/F = 240 ÷ 60 = 4 V/Hz. This means for every Hertz of frequency, the motor needs 4 Volts. If you reduce frequency to 30Hz, voltage should be 120V.

Standard V/F Ratios by Region

SystemVoltageFrequencyV/F RatioRegion
Single Phase120 V60 Hz2.0 V/HzNorth America
Single Phase230 V50 Hz4.6 V/HzEurope, Asia
Three Phase240 V60 Hz4.0 V/HzNorth America
Three Phase400 V50 Hz8.0 V/HzEurope
Three Phase480 V60 Hz8.0 V/HzNorth America (Industrial)
Three Phase690 V50 Hz13.8 V/HzIndustrial (High Power)

Step-by-Step Calculation Example

Problem: A VFD is running a 480V/60Hz motor at reduced speed with 360V applied. What is the operating frequency?

Step 1: Calculate the V/F ratio from nameplate data
V/F ratio = 480V ÷ 60Hz = 8 V/Hz

Step 2: Apply the voltage-to-frequency formula
Hz = V ÷ (V/F ratio) = 360V ÷ 8 V/Hz = 45 Hz

Answer: The motor is operating at 45 Hz, which is 75% of rated speed. For motor control calculations, see our Hz to RPM Calculator.

When to Use This Calculator

ApplicationUse CaseTypical V/F Ratio
Variable Frequency Drives (VFDs)Motor speed control in HVAC, pumps, conveyors4-8 V/Hz
Voltage-to-Frequency ConvertersAnalog sensor signal processingDevice-specific
Inverter DesignPower electronics developmentApplication-specific
Motor TestingDetermining operating parametersFrom motor nameplate
Energy Efficiency AnalysisOptimizing motor operationBased on load requirements

Motor Speed and Frequency Relationship

For AC induction motors, the synchronous speed is directly proportional to frequency. Use our Frequency Calculator for related calculations.

RPM = (120 × Hz) ÷ Poles
RPM = Motor speed (revolutions per minute) Poles = Number of motor poles (typically 2, 4, 6, or 8)

For a 4-pole motor at 60Hz: RPM = (120 × 60) ÷ 4 = 1800 RPM. At 45Hz (75% frequency), speed would be 1350 RPM.

Frequently Asked Questions

No, there is no direct physical conversion between Volts and Hertz because they measure different quantities—voltage measures electrical potential while frequency measures cycles per second. The V/F ratio is a device-specific parameter that relates them in applications like VFDs and motor drives.
Calculate it from your motor’s nameplate data: V/F ratio = Rated Voltage ÷ Rated Frequency. For a 230V/50Hz motor, V/F = 4.6 V/Hz. For a 480V/60Hz motor, V/F = 8 V/Hz. VFD manufacturers also provide recommended V/F curves in their documentation.
The V/F ratio maintains constant magnetic flux in the motor. If voltage is too high relative to frequency, the motor can overheat and saturate magnetically. If too low, the motor loses torque. Maintaining the correct ratio ensures efficient operation across the speed range.
The motor will run 20% faster (60/50 = 1.2), but if voltage isn’t adjusted, the V/F ratio changes. For a 230V/50Hz motor at 60Hz with same voltage: V/F drops from 4.6 to 3.83 V/Hz, reducing torque. Ideally, voltage should increase to 276V to maintain the ratio.
Voltage boost is extra voltage applied at low frequencies to overcome motor winding resistance and maintain torque. At very low speeds (below 5-10Hz), the standard V/F ratio doesn’t provide enough voltage. VFDs add a boost (typically 5-15% of rated voltage) to compensate.
The reverse calculation is: V = Hz × (V/F ratio). If you know the operating frequency and V/F ratio, you can determine the required voltage. For example, to run at 30Hz with a 4 V/Hz ratio: V = 30 × 4 = 120V. This calculator supports both directions.
Related Electrical Calculators
Hz to Voltage Calculator Hz to RPM Calculator Frequency Calculator Ohm’s Law Calculator Volts to Amps Calculator
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Author

  • Manish Kumar

    Manish holds a B.Tech in Electrical and Electronics Engineering (EEE) and an M.Tech in Power Systems, with over 10 years of experience in Metro Rail Systems, specializing in advanced rail infrastructure.

    He is also a NASM-certified fitness and nutrition coach with more than a decade of experience in weightlifting and fat loss coaching. With expertise in gym-based training, lifting techniques, and biomechanics, Manish combines his technical mindset with his passion for fitness.

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