Self-commissioning of a bearingless-motor drive

A method for self-commissioning a bearingless-motor drive, which includes a bearingless motor and a control unit of the bearingless motor, wherein the bearingless motor includes a stationary part and a movable part adapted to move relative to the stationary part, the motor including at least one winding, the method comprising:

• generating a magnetic model, which represents in a d, q coordinate system of the movable part a relationship between d-axis and q-axis current components, air gap length and d-axis and q-axis flux linkage components of the bearingless motor, the magnetic model comprising a plurality of constant parameters,
• supplying, while the movable part remains standstill, to the at least one winding at least two unequal d-axis current components and/or at least two unequal q-axis current components;
• measuring, with a magnetic sensor, d-axis and q-axis flux linkage components caused by said d-axis and q-axis current components, respectively;
• calculating, with the magnetic model d-axis and q-axis flux linkage components by inputting to the magnetic model d-axis and q-axis current component values equal to the d-axis and q-axis current components supplied to the at least one winding;
• and
• fitting, with a least-squares fitting algorithm, at least one constant parameter in the magnetic model such that the difference between the measured and calculated d-axis and q-axis flux linkage components will be minimized.

A method for condition monitoring of a bearingless-motor drive, the method comprising:

• generating a magnetic model, which represents a relationship between current, air gap length and flux linkage of the bearingless motor, the magnetic model comprising plurality of constant parameters,
• memorizing said plurality of constant parameters, parameters;
• supplying, to the at least one winding at least two unequal currents,
• measuring, by means of with a magnetic sensor, flux linkages caused by said at least two unequal currents respectively;
• calculating, with the magnetic model, flux linkages by inputting to the magnetic model current values equal to the currents supplied to the at least one winding;
• fitting, with a least-squares fitting algorithm, at least one constant parameter in the magnetic model such that the difference between the measured and calculated flux linkages will be minimized,
• comparing the fitted at least one constant parameter with the corresponding memorized parameter;
• and
• establishing a service request of the bearingless-motor drive on the basis of the comparison.