Audio frequency blocking filters

Audio frequency blocking filters prevent control signals that are transmitted, across power lines, by audio frequency transmission systems from dissipating in reactive power compensation equipment where they would cause unintended charging of capacitors.

MANGOLDT audio frequency blocking filters are precisely designed for the power of the downstream system and accurately coordinated with the audio frequency of the control system. They produce a very high impedance to this defined frequency. To effectively block the control signals while allowing all fundamental frequency currents pass with minimal loss.

Customized audio frequency filters are available for low or medium voltage.

Single blocking filters

Single blocking filters for use with power capacitors to prevent absorption of audio frequency signals by the capacitor.

Blocking filter blocks

Such filter blocks are used for blocking central, controlled compensation systems - i.e. with multiple capacitors.

Combined blocking filters

Audio frequency blocking filters can be expanded into combined blocking filters by using an upstream filter circuit reactor. As a compact system, they will then also protect controlled and uncontrolled compensation systems from overload that is caused by interference levels in the supply grid. For optimum performance and to prevent harmonic resonance in power systems having capacitors, they should always be sized series resonant frequencies due to capacitors on the system are not near characteristic harmonic frequencies.

Passage blocks

In addition to compensation systems, blocking filters protect the downstream consumers and distribution systems from audio frequency transmission signals. Additionally, they may be used to protect electrical systems from interference levels that may result when feeding in regeneratively produced energy from wind or solar parks. Separation of electrical systems of individual energy suppliers is possible as well.

Blocking filters

When audio frequency transmission signals cause interferences, improper switching or undesired resonances in electrical machines, facilities or lighting systems may occur. Audio frequency blocking devices – used as blocking filters – provide effective protection against the negative effects of these disturbances.


For questions about this product, please contact us.


B. Eng. (FH) René Thom
Phone: +49 241 166 07 - 42