DC chokes - smoothing chokes with iron core

Smoothing chokes are used in converter / rectifier circuits in the DC circuit. A direct current with an alternating current component is flowing through their windings.

Due to their inductance, the chokes limit the amplitudes of the proportional AC currents to a desired value and “smooth” the total DC current. Furthermore, current gaps (they depend on the converter output) can be reduced or avoided.

The inductance value of the choke, the arithmetic mean value of the direct current and the r.m.s. value and frequency of the alternating current are important design parameters. A parameter that can also provide information about the mechanical size of a DC choke with an iron core is the energy content L*I2 in [Ws].

The inductance value of a choke with an iron core is not linear, it decreases with increasing direct current. After saturation of the core, the inductance drops steeply, typically when the rated DC current or an agreed multiple is reached. The larger the inserted air gaps, the more similar the characteristic curve is to that of an air core coil.

On DC iron chokes designed with 2 identical windings on a so-called UI iron core, these windings can be connected either in parallel or in line, if they are not hard-wired (soldered) from the factory. (It should be remembered that the ratio of the inductance value to the number of turns is quadratic).

DC chokes air core coils

Smoothing chokes without an iron core are called air core inductors, air coils or ironless smoothing chokes. Cylindrical coils, also called solenoids, are more common than toroidal coils. The decisive advantage of air core inductors is the independence of the inductance value from the current and frequency over a wide range. The disadvantage is significantly smaller inductance values compared to an iron core choke.

Relatively large components are easily formed. The current rating of the winding conductor must be taken into attention. The coreless design results in advantages when insulating the windings against earth.
BREMER Transformatoren does not manufacture liquid-cooled components.

Your technical contact for inductors

If you have any product-specific questions, please contact Thomas Bremer. Together we will answer the last open questions regarding your enquiry.

Dipl.-Ing. Thomas Bremer: 03378 2006-0
E-Mail: thomas.bremer@bremer-trafo.de