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Rojony Khatun Author
Rojony Khatun
CalculatorToolsProjectExpert
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Małgorzata Koperska, MD Steven Wooding
Last updated: August 23, 2025

No Load Voltage Calculator: Open Circuit Voltage Tool

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No-load voltage calculator

Calculate the no-load (open circuit) voltage of generators, transformers, or other sources using EMF equations, winding data, and test parameters.

transformer no load voltag

An open-circuit voltage or no-load voltage is the voltage at which a power source is with no load present. This can be easily done with this calculator.

Formula & Table Summary:

Formula:

\( V_{NL} = E = 4.44 \times f \times N \times \Phi \)

no load voltage calculator

The No Load Voltage Calculator calculates the open-circuit voltage of an electric machine, or source without a load connected. It is a consideration of both the design and testing of generators, alternators, transformers, and other electrical systems, since it is close but not quite the same as the full-load voltage. The generated EMF and winding properties, and residual magnetism in the machine, determine the no-load voltage. The rated voltage, flux, and frequency can be found in alternators and transformers. This calculator returns the value of the open circuit voltage immediately by entering the crucial values such as EMF constant, velocity, and the number of turns. This can be used to predict performance and troubleshooting by engineers, electricians, and students without subjecting them to actual load.

no load voltage formula

Frequency (Hz)Turns (N)Flux (Wb)No-Load Voltage (V)
501000.02444
601000.02532.8
502000.02888
501000.01222

Frequently Asked Questions - No-load voltage calculator:

What is no-load voltage?

The voltage measured when a source has no connected load.

Where is it used?

In generators, alternators, transformers, and batteries.

Why is it higher than full-load voltage?

Because there is no voltage drop due to load current.

Does frequency affect it?

Yes, directly proportional in AC machines.

Can I measure it directly?

Yes, with a voltmeter and no connected load.

What causes no-load voltage to drop?

Loss of residual magnetism or winding faults.

What is the formula?

VNL = 4.44 × f × N × Φ.

Can I use this for DC generators?

Yes, but formula differs slightly.

Is it safe to run no-load for long?

Generally yes, but not for all machines.

Does temperature affect it?

Yes, as it changes winding resistance.

Rojony Khatun

Rojony Khatun

CalculatorToolsProject

Rojony Khatun is the creator of a free online tools website designed to simplify everyday and engineering-related calculations for students, professionals, and hobbyists. The platform offers a wide variety of basic and advanced calculators across key categories, including Electrical Calculators, Electronic Calculators, and Time & Date Calculators, helping users solve problems quickly and accurately.