Hz To Voltage Calculator

Hz to Voltage Calculator

Calculate required voltage from operating frequency using V/F ratio for VFDs and motor control

⚡
Key Point: To find voltage from frequency, multiply frequency by the V/F ratio: V = Hz × (V/F ratio). This determines what voltage to apply at any operating frequency in VFD applications.
Quick Presets (Common Motor Frequencies)
Calculated Voltage
0 V
= 0 mV
📝 Calculation Steps
⚙️ Motor Speed Estimate
💡 Voltage Level Assessment
Hz To Voltage Calculator
Table of Contents

How to Convert Hertz to Voltage Using V/F Ratio

Hertz (Hz) and Volts (V) are fundamentally different electrical quantities—frequency measures how many cycles an AC waveform completes per second, while voltage measures electrical potential. Direct conversion between them is not physically possible because they describe different properties.

However, in Variable Frequency Drives (VFDs) and AC motor control systems, these quantities are linked through the V/F ratio. This ratio determines what voltage should be applied at any given operating frequency to maintain optimal motor performance and prevent overheating.

The Hz to Voltage Formula

V = Hz × (V/F ratio)
V = Required Voltage (Volts) Hz = Operating Frequency (Hertz) V/F ratio = Volts per Hertz

This formula is essential for VFD programming. When you reduce motor speed by lowering frequency, you must also reduce voltage proportionally. According to Wikipedia’s article on VFDs, maintaining the correct V/F ratio ensures constant motor flux and torque capability.

Why V/F Ratio Matters in Motor Control

The V/F ratio controls the magnetic flux in AC induction motors. When you calculate voltage from frequency using this ratio, you ensure:

✓
Constant Torque: Proper V/F ratio maintains full torque capability across the speed range. Too low voltage at a given frequency reduces torque; too high causes overheating and magnetic saturation.

Standard V/F Ratios Reference Table

Motor RatingBase FrequencyBase VoltageV/F Ratio
US Single Phase60 Hz120 V2.0 V/Hz
US Three Phase60 Hz240 V4.0 V/Hz
EU Single Phase50 Hz230 V4.6 V/Hz
EU Three Phase50 Hz400 V8.0 V/Hz
US Industrial60 Hz480 V8.0 V/Hz
High Power50 Hz690 V13.8 V/Hz

Step-by-Step Calculation Example

Problem: A VFD needs to run a 480V/60Hz motor at 45Hz. What voltage should be applied?

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

Step 2: Apply the Hz to Voltage formula
V = Hz × (V/F ratio) = 45Hz × 8 V/Hz = 360V

Result: Apply 360V at 45Hz to maintain proper motor operation. For related calculations, use our Volts to Hz Calculator.

Voltage at Different Frequencies

Operating Frequency% of Base SpeedVoltage (4 V/Hz)Voltage (8 V/Hz)
60 Hz100%240 V480 V
45 Hz75%180 V360 V
30 Hz50%120 V240 V
15 Hz25%60 V120 V
6 Hz10%24 V + boost48 V + boost

Note: At very low frequencies (below 5-10 Hz), VFDs typically add “voltage boost” to compensate for motor winding resistance and maintain starting torque. Learn more about motor control with our Hz to RPM Calculator.

Frequently Asked Questions

No. Hz (frequency) and Volts (voltage) measure completely different physical properties. The V/F ratio is a device-specific parameter that defines how voltage and frequency are related in motor drives. Without knowing this ratio, there is no way to calculate one from the other.
Divide your motor’s rated voltage by its rated frequency. For example: A 230V/50Hz motor has a V/F ratio of 230÷50 = 4.6 V/Hz. A 480V/60Hz motor has a V/F ratio of 480÷60 = 8 V/Hz. This information is on the motor nameplate.
The motor will have reduced torque and may not be able to drive the load. In severe cases, the motor may stall or overheat trying to maintain load. Always maintain the correct V/F ratio when adjusting motor speed.
Voltage boost adds extra voltage at low frequencies (typically below 5-10 Hz) to overcome motor winding resistance. At very low speeds, the standard V/F calculation produces voltage so low that motor resistance losses become significant, reducing available torque. Boost is typically 5-15% of rated voltage.
Yes, but with limitations. Above base frequency, voltage is typically held constant (at rated voltage) while frequency increases. This is called “field weakening” and results in reduced torque capability. Motor bearings and mechanical limits must also be considered for high-speed operation.
Hz measures the frequency of the AC power supply (cycles per second). RPM measures how fast the motor shaft rotates (revolutions per minute). They are related by the formula: RPM = (120 × Hz) ÷ Poles. A 4-pole motor at 60Hz runs at 1800 RPM synchronous speed.
Related Electrical Calculators
Volts to Hz Calculator Hz to RPM Calculator Angular Velocity Calculator Frequency Calculator Volts to Kilowatts Calculator
`); w.document.close(); };window.htvToggleFaq = function(btn) { const item = btn.closest('.htv-faq-item'); document.querySelectorAll('.htv-faq-item').forEach(i => { if (i !== item) i.classList.remove('active'); }); item.classList.toggle('active'); }; })();

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.

Leave a Comment