Electrical Inductance Converter

Electrical inductance is a property of an electrical conductor that opposes changes in current flow. When current through an inductor changes, it creates a magnetic field that induces a voltage opposing that change - a phenomenon known as Lenz's law. The SI unit of inductance is the Henry (H), named after American scientist Joseph Henry. Inductors are fundamental components in power supplies, radio frequency circuits, filters, and transformers. This comprehensive inductance converter helps engineers and hobbyists quickly convert between the various unit prefixes used in electronics design and specifications.

The Henry: A Practical Unit

One Henry is defined as the inductance that produces one Volt of electromotive force when current changes at one Ampere per second. Unlike the Farad for capacitance, the Henry is a practical-sized unit for many applications. Power supply filter inductors often range from 1-100 mH. Audio crossover inductors may be in the 0.1-10 mH range. However, RF applications typically use much smaller values - microhenrys or even nanohenrys - because higher frequencies require less inductance for the same impedance. Large power transformers can have inductances of several Henrys on their primary windings.

Millihenrys: Power Electronics and Audio

Millihenrys (mH) are commonly used in power electronics and audio applications. Switching power supply output inductors typically range from 10-1000 µH (0.01-1 mH). Loudspeaker crossover networks use inductors in the 0.1-5 mH range to filter low frequencies to woofers. Motor drive filters often specify inductances in millihenrys. Common-mode chokes for EMI filtering are frequently rated in the 1-50 mH range. Understanding these values helps in selecting appropriate components for audio and power applications.

Microhenrys and Nanohenrys: RF Applications

Radio frequency circuits predominantly use microhenrys (µH) and nanohenrys (nH) because inductor impedance (XL = 2πfL) increases with frequency. At 100 MHz, a 100 nH inductor has an impedance of about 63 Ohms - useful for RF matching networks. RF chokes for blocking high frequencies while passing DC typically range from 100 nH to 100 µH. Antenna matching networks, oscillator tank circuits, and RF filters all specify inductance in these smaller units. PCB trace inductance (roughly 1 nH per mm) becomes significant at gigahertz frequencies, affecting high-speed digital design.

Electrical Inductance Conversion Reference

• 1 Henry (H) = 1,000 mH = 1,000,000 µH = 10⁹ nH
• 1 Millihenry (mH) = 0.001 H = 1,000 µH = 10⁶ nH
• 1 Microhenry (µH) = 0.001 mH = 10⁻⁶ H = 1,000 nH
• 1 Nanohenry (nH) = 0.001 µH = 10⁻⁹ H
• Reactance: XL (Ω) = 2π × frequency (Hz) × L (H)

Practical Applications

• Power Supplies: Sizing filter inductors for switching converters
• RF Design: Matching networks, tank circuits, and RF chokes
• Audio Crossovers: Designing loudspeaker frequency dividing networks
• EMI Filtering: Common-mode and differential-mode noise suppression
• Transformer Design: Calculating primary and secondary inductances
• Motor Drives: Specifying filter components for variable frequency drives