In
electrical engineering
Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...
, the K-factor of a
power transformer
Power may refer to:
Common meanings
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power, a type of energy
* Power (social and political), the ability to influence people or events
Ma ...
is a measure of how well it can handle
harmonic distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...
. Transformers which are designed to handle harmonic distortion are referred to as K-rated transformers.
Harmonics
In an
alternating current
Alternating current (AC) is an electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction. Alternating current is the form in w ...
power system, electrical energy is ideally transmitted as a pure sine wave, typically at a fundamental frequency of 50 Hz or 60 Hz. However,
switching can lead to distortion in the power system, resulting in a non-sinusoidal waveform. This deviation from a pure sinusoidal waveform is measured using
harmonics
In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the ''fundamental frequency'' of a periodic signal. The fundamental frequency is also called the ''1st harm ...
. The th harmonic is a waveform at an integer multiple of the fundamental frequency. For example, a wave transmitted with a fundamental frequency of 60 Hz would have its 2nd harmonic at 120 Hz, its 3rd harmonic at 180 Hz, its 4th harmonic at 240 Hz, and so on. The waveform is considered to be a sum of all harmonic components.
A K-rated power transformer is one that is designed to withstand this harmonic distortion. The K-factor is a measure of how well it mitigates distortion.
Calculation
The following formula is used to calculate the K-factor of a transformer:
:
Where:
* is the K-factor
* is the harmonic order
* is the per-unit current at the th harmonic order
Typical Values
The following table lists typical K-factors used depending on the harmonics produced by the loads:
[
Transformers with a larger K-factor are more expensive.][
]
References
Electric transformers
Electrical parameters
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