EMI suppression cores

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Snap-on ferrite beads
Toroidal ferrite bead

EMI suppression cores a.k.a. ferrite beads are an efficient way to reduce high frequency interference from wiring. Running cable through a ferrite beads is recommended solution attempt if signal reliability problems are encountered.

Selection

For motor control applications it is recommended to get low to medium frequency ferrite beads for maximum efficiency.

Preferred types
  • Core material designed for low to medium frequency bands (attenuation between 1-300 MHz)
  • Large enough to fit cable multiple rounds through it
Avoid, might make things worse
  • Core material designed for high frequency bands (above 300 MHz)
  • Inductor cores
  • Iron powder cores

Warning: most ferrite & iron powder cores look same. If unsure about material properties, its most safe to purchase new low to medium frequency beads.

Where to find suitable cores

Ferrite beads are available from most electronic part distributors such as:

  • Digikey
  • Mouser
  • Farnell

Some popular ferrite bead brands:

  • Laird-Signal Integrity Products
  • Fair-Rite

Usage with VSD-E/XE drives

To solve an EMI problem its good to have selection of beads that can be tried on different cables. Most typical placement for beads:

  • USB adapter
  • CMD cable
  • Encoder cable
  • Motor output cable (all motor wires through core, multiple turns)
  • HV DC power supply cable (+ and - leads through core, multiple turns)

Note: don't run multiple cables through one bead.

See also


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