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A4018_ELH • 2/10/2016

Snap-In Aluminum Electrolytic Capacitors – ELH Series, +85ºC

Impedance (Z)

Impedance of an electrolytic capacitor results from a circuit formed by the following individual equivalent series components:

L

C

o

R

e

L

C

e

C

R

etc.)

C

L = Inductive reactance of the capacitor winding and terminals

Impedance of an electrolytic capacitor is not a constant quantity that retains its value under all conditions; it changes depending on

frequency and temperature.

Impedance as a function of frequency (sinusoidal waveform) for a certain temperature can be represented as follows:

L

0.1

1

10

100

1000

10000

0.1

1

10

100

1000

Z [ohm]

F [KHz]

B

C

A

1/ω

ω

ω

ω Co

Re

1/ω

ω

ω

ω

Ce

ωL

• Capacitive reactance predominates at low frequencies

• With increasing frequency, capacitive reactance Xc = 1/ωC

resistance R

• At even higher frequencies, resistance of the electrolyte predominates: Z = R

• When the capacitor’s resonance frequency is reached (ω

1/ωC

• Above this frequency, inductive reactance of the winding and its terminals (XL = Z = ωL) becomes effective and leads to an increase

in impedance

Generally speaking, it can be estimated that C