Posted on 12 April 2019

Equivalent Series Resistance (ESR) for Capacitors








Normally, the resistive losses of capacitors are denoted as the dissipation factor tan δ. In the case of bigger capacitance values, especially of class-II-capacitors, which are predominantly deployed for current supply, the data sheets of producers specify the Equivalent Series Resistance (ESR) in place of tan δ. ESR combines the resistive losses and the dielectric losses. This implies that:


where C is  capacitance and ω is angular frequency.

Aluminum and electrolytic capacitors have higher ESR values tending to increase with frequency. On the other hand, ceramic capacitors have much less ESR values compared to electrolytic capacitors, and non-electrolytic capacitors or ceramic capacitors can be treated as ideal components.

A very serious problem, particularly with aluminum electrolytic capacitors, is that ESR increases over time with use. ESR can even increase enough to cause circuit malfunction and component damage. High temperatures and ripple current exacerbate the problem. In a circuit with significant ripple current, an increase in ESR will increase heat dissipation, thus accelerating aging. The ESR of capacitors of relatively high capacitance (from about 1 μF),  is easily measured in-circuit with an ESR meter.


For further information on aluminum electrolytic capacitors, please read the following articles:

Capacitor Bank Design

Calculating the Useful Life of Capacitors

Film Capacitors for DC-Link

Mounting Positions of Aluminum Electrolytic Capacitors with Screw Terminals


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