Variable capacitor

QuickField simulation example

Variable air capacitor consists of fixed stator plates and movable rotor. Capacitance between the stator plates depends on the position of the rotor.

Engineering question
How to find capacitance versus rotor position in variable air capacitor?

Engineering answer
Set up a 3D QuickField Electrostatics problem for a variable air capacitor and evaluate capacitance versus rotor position from computed field results.

Typical applications
variable air capacitors, tuning capacitors, rotor-stator plate capacitors

• Download simulation files (files may be viewed using any QuickField Edition).

Problem Type electrostatics.

Geometry 3D extrusion.

Given
Relative permittivity of air ε = 1,
Potential difference ΔU = 1000 V

Task
Find the mutual capacitance between two stators as a function of the rotor position.

Solution
QuickField simulation gives energy W and electric potential U distribution. The capacitance then can be calculated as C = 2W / ΔU².

Results

• Video: Variable capacitor. Watch on YouTube