Glossary · Motion control and drives

Commutation

Also known as: Electronic commutation

German: Kommutierung

In electric motors, commutation is the switching of current between the windings in step with the rotor position so that the motor produces continuous torque. It is done mechanically by brushes in DC motors and electronically by the drive in brushless motors.

Motion control

In one sentence

Commutation switches motor winding currents in step with the rotor position so the motor keeps producing torque.

Example

After replacing the encoder on a servo motor, the technician runs the drive's commutation offset routine before enabling the axis.

How it applies

Engineering: Electronic commutation needs the rotor's electrical angle. It comes from Hall sensors, an absolute encoder with a known offset, or a phasing routine at startup.
Commissioning: Wrong commutation offset leads to reduced torque, overheating or uncontrolled motion. Some phasing routines move the motor a small distance, which must be permitted at that moment.
Maintenance: Replacing a motor or encoder can invalidate the stored offset.
Documentation: In the Maintenance manual, write the offset or phasing procedure as a DITA task with a safety note: the axis may move unexpectedly during phasing, so the hazard zone must be clear and vertical axes secured.

Commutation vs. field-oriented control

Commutation is the basic task of feeding the right winding at the right time. Field-oriented control (FOC) is a control method that performs this with sinusoidal currents and controls torque and flux separately; it includes commutation.