EMI suppression cores

From Granite Devices Knowledge Wiki
Revision as of 14:45, 4 March 2014 by Tero K (Talk | contribs) (Application)


Jump to: navigation, search
Snap-on ferrite cores
Toroidal ferrite core

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

Selection

For motor control applications it is recommended to get low to medium frequency ferrite cores 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
  • Most ferrite & iron powder cores look same. If unsure about material properties, its most safe to purchase new low to medium frequency cores.

As example, take a look at Laird broadband and low frequency cores.

Where to find suitable cores

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

  • Digikey
  • Mouser
  • Farnell

Some popular ferrite core brands:

  • Laird-Signal Integrity Products
  • Fair-Rite

Usage

Application

Turning cable 2-3 times through core or using multiple in series increases filtering performance.

Application tips:

  • If possible, make 2-3 turns of cable through one core to maximize it's effectiveness
  • Place core close to interference source, not in the middle of the cable

With servo drives

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

  • Motor output cable (all motor wires through core but not earth conductor). However, if earth conductor is hard to separate, then feeding all wires through core is still better than nothing.
  • High voltage power supply cable (+ and - leads through core)
  • USB adapter or other communication cables
  • Control I/O cables
  • Encoder/feedback device cable

See also


In no event the Product Information or parts hereof shall be regarded as guarantee of conditions or characteristics. The Product Information or any part thereof may also not be regarded as a warranty of any kind. No liability of any kind shall be assumed by Author with respect to Product Information or any use made by you thereof, nor shall Author indemnify you against or be liable for any third party claims with respect to such information or any use thereof.

As content of this Wiki may be edited by user community, Granite Devices Oy or it's affiliates do not take any responsibility of the contents of this Wiki. Use information at your own risk. However, Granite Devices staff attempts to review all changes made to this Wiki and keep information trustworthy.

Without written consent, Granite Devices' Products or Intellectual Property shall not be used in situations or installations where living beings, material property, or immaterial property could be harmed by the operation, features or failures of Product. Products may only be used in a way where hazards like moving parts, electric shock, laser radiation, or fire can't be realized even if the content of this Wiki would suggest otherwise.