Generator Frequency Calculator
Compute generator output frequency (N poles × M rpm): f = (P × N) / 120. Hz output for Brazil (60) and Europe (50).
Synchronous generator frequency: f = (P · n) / 120
In an AC synchronous generator, output frequency is locked to the rotor speed by f = (P · n) / 120, where P is the number of magnetic poles and n is the shaft speed in RPM. For Brazil's 60 Hz grid: 2 poles need 3600 RPM, 4 poles need 1800 RPM, 6 poles need 1200 RPM. Europe and much of Asia use 50 Hz; Itaipu generates both — half of its 20 turbines run at 50 Hz for Paraguay, the other half at 60 Hz for Brazil, decoupled by a DC link. Example: a 4-pole machine at 1800 RPM gives f = (4 · 1800) / 120 = 60 Hz. Hydro units use 64–100 poles at low speed; wind turbines run variable speed and synthesize 60 Hz through a back-to-back converter (rectify, then invert).
Applications: diesel gensets, hydro, wind
This relation drives the design of diesel gensets, hydroelectric units (Itaipu's 20 × 700 MW machines), turbo-generators in thermal plants, and selection of pole count for wind generators with full-power converters. It also dictates RPM targets for synchronizing a new unit to the grid.
FAQ
Why the constant 120? It combines 60 s/min with the factor of 2 between pole pairs and poles: f [Hz] = (pole pairs · RPM) / 60, and poles = 2 · pole pairs.
Can I run a 60 Hz machine at 50 Hz? Only if you reduce speed proportionally and accept lower output; flux and cooling must still be checked.
Why so many poles in hydro units? Water turbines spin slowly (90–200 RPM); more poles produce 60 Hz without a gearbox.
Does the load change frequency? No — frequency tracks shaft speed. The governor adjusts torque to keep RPM constant as load varies.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.