Hello, I’m going to check the word ‘linear / Non-linear’ in this post.
When you read some mathematical or electrical documents, you can find ‘linear or non-linear’ easily.
1. What is the meaning of ‘Linear / Non-linear’ ?
What is the ‘Linear’ and ‘Non-linear’?
To figure it out firstly, I checked the definition of dictionary.
* Linearity
– ‘Linearity’ from wikipedia
– Linearity is the property of a mathematical relationship that can be graphically represented as a straight line. Linearity is closely related to proportionality. Examples in physics include the linear relationship of voltage and current in an electrical conductor(Ohm’s law), and the relationship of mass and weight. By contrast, more complicated relationships are nonlinear.
– In mathematics, f(x) is a function that satisfies the two properties :
① Additivity
– f(x+y) = f(x) + f(y)
② Homogeneity
– f(ax) = af(x)
2.Linear circuits?
If you search “Power factor” in Wikipedia, you can read some contents about Linear circuits
Linear circuits have a sinusoidal response to the sinusoidal line voltage. A linear load does not change the shape of the input waveform but may change the relative timing(phase) between voltage and current, due to its inductance or capacitance.
– ‘Power factor’ from wikipedia
Where reactive loads are present, such as with capacitors or inductors, energy storage in the loads results in a phase difference between the current and voltage waveforms. During each cycle of the AC voltage, extra energy, in addition to any energy consumed in the load, is temporarily stored in the load in electric or magnetic fields then returned to the power grid a faction of the period later.
According to resistive, inductive and capacitive loads, the phase can be changed. But, the shape of the waveform is still sinusoidal.
- Inductive load stores in the load in magnetic field
- Capacitive load stores in the load in electrical field
3. Non-linear load?
Then, What kind of non-linear loads exist?
When we commutate AC to DC, we usually use diode rectifier.
In this case, although the input voltage is sinusoidal, the input current is not sinusoidal. Because diodes act like switches. As the condition of voltage level, diode can be turned on/off.
Thus, it can not be a sinusoidal current waveform.
