Parallel and series connection of capacitors. Capacitor bank capacity

Definition of capacitor capacitance

The electrical capacitance of a capacitor is the physical quantity equal to the ratio of the charge on one of the capacitor’s conductors to the potential difference between its plates. In the International System of Units (SI), electrical capacitance is measured in farads.

Definition of capacitor bank capacity

A system formed by connecting several capacitors with conductors, neglecting the small capacitance of the wires, is called a capacitor bank. In most cases, a capacitor bank can be considered as a single capacitor with capacitance C. This equivalent capacitance is called the capacitor bank capacity.

Parallel connection of capacitors

If in a system of two capacitors with capacitances C₁ and C₂ the plates of different capacitors are connected in pairs (the bank contains two isolated conductors), such a connection is called parallel. Two or more capacitors connected in parallel can always be replaced with a single capacitor having some equivalent capacitance C.

The capacitance of a parallel capacitor bank is equal to the sum of the capacitances of the individual capacitors.

C_{parallel bank} = C₁ + C₂ + ... + C_n

Series connection of capacitors

If in two capacitors with capacitances C₁ and C₂ one pair of plates is connected together (the bank contains three isolated conductors), such a connection is called series. Series-connected capacitors can be considered as a single new capacitor only if the plates connected together are overall electrically neutral (the potential difference between plates of different capacitors connected by a conductor is zero).

For a series connection of capacitors, the reciprocals of their capacitances are summed. It should be emphasized that this is only valid if the total charge on each pair of connected plates is zero.

1/C_{series bank} = 1/C₁ + 1/C₂ + ... + 1/C_n

Capacitor bank total capacity calculation