“Ground the motor” can refer to three different tasks. Protective bonding provides a fault-current path; screen termination controls electromagnetic currents; shaft or bearing measures manage common-mode current through the rotor system.
| Path | Purpose | Evidence before energisation |
|---|---|---|
| PE conductor/frame bond | Electrical safety | Drawing, conductor size and continuity test |
| Cable screen/armour | EMC and return path | Gland and termination detail |
| Base/skid bonds | Equipotential connection | Installed bonding inspection |
| Shaft/bearing measure | Bearing-current control | Approved drive-motor design |
Remove paint only where the approved bonding detail requires metal contact, then protect the joint against corrosion. Keep power, control and instrumentation routing consistent with the project EMC plan.
For VFD systems, review drive topology, cable type and length, motor size, switching conditions and bearing arrangement together. Never add an insulated bearing or shaft brush in isolation without confirming the intended current path.
The handover pack should contain the grounding drawing, cable schedule, gland details, torque record, continuity result and any bearing-current provisions.
Related reading: VFD cable length and filters and motor bearing current.