Related to practical equivalent circuits of elements

[timkuc]

Why the practical equivalent circuits of these elements (Ideal L,C and quartz crystal ) are like this ? (Reasons/concept behind for adapting these practical equivalent circuits)

L https://obrazki.elektroda.pl/8264707200_1412987588.jpg


C https://obrazki.elektroda.pl/6714149500_1412987634.jpg

Quartz Crystal https://obrazki.elektroda.pl/8730213500_1412987703.jpg

 

[Nanda Sinha]

I think these are practical results.

 

[Venkadesh_M]

Because every wire has resistance, every dielectric material has leakage in practical.

 

[D.A.(Tony)Stewart]

Every inductor has interwinding capacitance that results in a self resonant frequency (SRF) which is found on most specs for RF types.

The winding resistance is critical for chokes to minimize self-heating. The part not shown in the equiv cct. Is the non-linear drop in inductance, when approaching saturation.

Similarly, ceramic caps often drop in capacitance as it approaches the max voltage rating. All caps has an effective series resistance (ESR) often rated in electrolytic types, as well as a leakage parallel resistance.

The most ideal small value cap is Mica for high voltage rating and low ESR for use in transformer tape insulation and high power RF types.

In larger C values, Teflon and other Plastics have the best RC time constant for leakage with high voltage rating , lower dielectric constant than electrolytics.

Plastic Caps are often found in UPS, telephone circuits, Induction Heaters, long T integrators, and HV power factor correction racks on the grid for large VAR values, due to low leakage and hi V rating and low ESR.

Crystals also have a similar equivalent of a large transformer inductance in Henries but a tiny motional capacitance <0.1 picofarads in series , with a low series resistance <200R in series. Then small,parallel caps e.g.10pF-30pF are specified for parallel tuning the crystal to over-ride stray capacitance variations (1pF) and set the room temp nominal frequency in parallel resonance.