Glossary · Motion control and drives
Field-oriented control (FOC)
Also known as: Vector control, FOC
German: Feldorientierte Regelung
In drive control, field-oriented control (FOC) is a control method for AC motors that transforms the stator currents into a rotating coordinate system aligned with the rotor flux and controls the flux-producing and torque-producing current components separately.
- Motion control
In one sentence
Field-oriented control splits AC motor current into flux- and torque-producing parts and controls them separately, like a DC motor.
Example
A servo drive uses field-oriented control with encoder feedback to hold full torque at standstill on a PMSM.
How it applies
- Engineering: FOC is the standard control method in servo drives and many frequency inverters. It needs the rotor flux angle from an encoder or from a motor model (sensorless vector control).
- Commissioning: Motor data identification, encoder alignment and current loop tuning are prerequisites; wrong values cause poor torque or instability.
- Operation: FOC allows high torque at low speed and fast torque changes.
- Documentation: Drive parameter lists often offer control modes such as V/f, sensorless vector and closed-loop vector. Explain the practical difference and when each is appropriate, and keep the manufacturer's names consistent in UI texts and manuals.
Field-oriented control vs. V/f control
V/f (volts per hertz) control keeps the ratio of voltage to frequency constant and has no torque control; it suits fans and pumps. FOC controls torque directly and suits dynamic or positioning tasks.