EMI suppression cores
EMI suppression cores a.k.a. ferrite beads are an efficient way to reduce high frequency interference from wiring. Adding ferrite beads to signal & power wiring is recommended 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. So if unsure about material properties, its most safe bet to purchase 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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