Definition
The standard frequencies at which alternating current (AC) electrical power is generated and distributed. In aircraft electrical systems, the standard power frequency is 400 hertz (cycles per second), while ground-based commercial power in most countries is either 60 hertz (North America) or 50 hertz (much of Europe and elsewhere).
Plain English
How many times per second the alternating current in an electrical system reverses direction. Aircraft use 400 times per second; household power on the ground uses 50 or 60.
Context Anchor
Seen in aircraft electrical-system descriptions, generator specifications, inverter checks, and external power requirements.
Derivation
Frequency comes from a Latin word meaning repeated occurrence. That helps here because a power frequency is simply how often the electrical cycle repeats each second.
Why Pilots Care
Matching the correct power frequency prevents overheating, instrument failure, or damage to electrical equipment.
Intuition Check
Do not confuse power frequencies with radio frequencies. Power frequencies describe electrical power supplied to equipment, not communication or navigation channels.
Example Sentence 1
The aircraft's avionics are designed for the 400-hertz power frequency supplied by the onboard generators.
Example Sentence 2
Avionics units are designed to operate only within specific power frequencies to avoid damage from mismatched electrical supply.