Example of a capacitor

Capacitor with dielectric

Let us consider a Steady state AC Electric problem comprising a real capacitor and a voltage source applied at its terminals. The problem does not contain another voltage supply.

With:

• V_eff, the rms value of the voltage applied to the capacitor, and ω the pulsation,
• the resistance R (in Ω) and the capacitance C (in F) of the equivalent RC parallel circuit of the capacitor. The dielectric material of the capacitor is supposed to be linear in order to enable the definition of the capacitance C.

Capacitance and resistance of the capacitor

The complex apparent power S (in VA) of the capacitor has the expression: S = P + j Q

where:

• P is the active power (in W):
• Q is the reactive power (in VAr):

From the active power of the capacitor we can compute the equivalent resistance:

From the active power of the capacitor we can compute the equivalent capacitance: