Common-mode chokes address current shared by conductors relative to earth. They do not correct every differential-mode harmonic or replace bonding, shield termination and a low-inductance return path.
Map common-mode current before adding impedance
First verify 360-degree motor-cable shield termination, enclosure bonding and PE continuity. Then use measurements to distinguish bearing current, encoder disturbance and conducted emissions. A choke chosen without this diagnosis may shift the resonance.
Current-path review
| Item | Engineering purpose | Review action |
|---|---|---|
| Source | Drive switching edges | Identify voltage and carrier settings |
| Path | Cable, frame and bearings | Measure where current closes |
| Choke | Common-mode impedance | Check saturation and heating |
| Bonding | Shield and PE connections | Reduce uncontrolled return paths |
Evidence required before approval
Document core material, turns, conductor arrangement, current rating and temperature rise. Repeat measurements after installation and retain before-and-after spectra under comparable load.
Retain the equipment revision and test record. Name the reviewer. Keep open assumptions visible.
Commissioning decision
Never approve a copied setting. Confirm interface compatibility and operating limits. Exercise the intended response during a functional test.