Common-mode suppression chokes

Within a common mode suppression choke unwanted signals, which are present on both conductors, are being coupled in opposite direction cancelling each other out. The frequency range in which this happens is limited though. In order to include the optimal common mode suppression choke into your design we recommend to get in contact with us.

Common-mode suppression chokes < 10 [MHz]

The toroid cores are being produced from ferrite allowing for a high inductance. The compact size minimizes stray fields. The higher the inductance the earlier the choke is being driven into saturation. A choke with multilayer windings is affected by parasitic capacitance, reducing the chokes effectiveness at higher frequencies. In practice a common mode suppression choke with 2 x 1 [mH] inductors is more effective than a common mode suppression choke with 2 x 10 [mH] inductors.

Application areas:

  • EMI suppression of switching power supplies and frequency converters, line-side and load-side.
  • EMI suppression of clock frequencies and harmonics on power lines, signal lines and transmission lines.
  • Increase the immunity against asymmetrical disturbances, such as EFT, injected and radio wave injected disturbances.
  • Suitable as 1:1 transformer for signals under 10 [MHz].

Common-mode suppression chokes > 10 [MHz]

These chokes are made from a special ferrite with high impedance providing good attenuation against frequencies above 10 [MHz]. The ferrite has lower permeability due to which the inductance value is reduced in comparison to a same sized choke which was built against frequencies below 10 [MHz]. This is perfectly acceptable since for higher frequencies sufficient suppression is achieved using lower inductances.

The chokes are wound with a single layer, minimizing capacitive coupling, making them efficiently reactive in a wideband frequency range. These chokes are available in open versions only. Potting would act as dielectric, increasing the capacitive coupling.

Application areas:

  • EMI suppression of common mode signals on power lines, data lines, signal lines and transmission lines.
  • Suppression of bursts and unintended received radio signals on symmetrical data lines, such as RD-485, RS-422, 4-20 [mA], current loops, CAN-bus, etc.
  • Possible to combine with chokes for lower frequencies.
  • Galvanically separated transmission of pulses and high frequency signals above 10 [MHz].