Frequency counts complete cycles.
A cycle is one complete repeat of a waveform. Frequency is the number of cycles per second, measured in hertz (Hz). A 50 Hz waveform completes 50 cycles each second.
The period is the time taken for one cycle. At 50 Hz, one cycle takes 1 ÷ 50 second, or 20 milliseconds.
More cycles in the same time.
If both plots show the same time interval, the lower wave has twice the frequency. Their peaks are the same height, so their amplitude is unchanged.
Amplitude and phase describe different things.
Amplitude describes the size of a waveform. Phase describes where it is within its cycle relative to a reference. One complete cycle corresponds to 360 electrical degrees.
Two waves can have the same frequency and amplitude but reach their peaks at different times. That timing relationship is central to three-phase electricity.
A drive has more than one relevant frequency.
The fundamental output frequency is associated with the motor’s rotating magnetic field. The much faster switching frequency describes the electronic switching used to create the output.
Neither is simply the number of lift journeys per minute. The motor and mechanical arrangement determine how electrical operation becomes car movement.
A closer look
A non-sinusoidal repeating waveform can be represented as a fundamental component plus harmonics. Harmonics have frequencies at whole-number multiples of the fundamental; they describe waveform shape, not extra independent mains supplies.
Check your understanding
If frequency doubles from 25 Hz to 50 Hz, what happens to the period?
Reveal the explanation
It halves: from 40 milliseconds to 20 milliseconds. The amplitude does not have to change.