Driving an ACIM (AC induction machine)

The induction motor is outside the primary focus of our customers. Nevertheless, our driver is well suited for this type of motor. There are two supported methods:

• U/f mode. This is the simple, widely recognized control method, commonly referred to as "variable frequency drive" for induction motors. The frequency is coupled to the output voltage. This method is easy to configure, offers a stable operation, but only the voltage mode is supported. Current control / torque control is provided indirectly, through imult command / iref parameter.

• FOC mode. Employs the full FOC with axes separation, working with the slip angle and enabling more precise control. With this type, the induction motor achieves most of the drive modes we normally introduce for a PMSM.

How to configure

tip

Automatic identification is not offered for this type of motor. We recommend consulting our technical support team for assistance.

• set /driver/psi to 0 (no flux linkage in the squirrel cage).

For U/F mode

• set /driver/dac/dxc to $\sqrt{2}/2$ (roughly $0.707$) set direct axis current limit to match the quadrature axis current limit.

• set /driver/vcf to $12$ (disable current control in direct axis, choosing VFD mode). You may experiment with values of 4 and 8 for directional preferences.

• set /driver/dac/mtk to $0$. Alternatively, use /driver/dac/mtk to achieve a degree of torque control: the d- current reference is mapped to the q- current measurement (through filter defined by mtk).

• set /driver/prest to $0$ (asynchronous mode - decouple the field angle from the rotor).

• set /driver/rest/omega to the desired ratio $r$ between the voltage and the frequency. It can be calculated with this equation:

  $r = \frac{2\pi \cdot f}{U_{stator,RMS} \cdot \sqrt{2/3}}$

  where $f$ is the rated electrical frequency and $U_{stator,RMS}$ is the rated phase-to-phase RMS voltage. The motor manufacturer should specify those ratings.

tip

A fine tuning by hand might be advisory for /driver/rest/omega, as different vendors rate motors differently. The tuning goal is to find the minimum Q-current of unloaded motor (in voltage drive command).

For FOC mode

• set /driver/dac/dxc to $\sqrt{2}/2$ (roughly $0.707$) set direct axis current limit to match the quadrature axis current limit. The d- current reference is mapped to the q- current measurement (through mtk filter).
• set /driver/prest to the value representing your motor sensor (usually, a quadrature encoder). Do not forget to set the correct ppr (for encoder) and rpole mapping. rpole can be auto-identified with the identrun procedure (as long as the encoder's resolution is more than 360 ppr). Keep the /driver/psi at zero.
• set /driver/rest/omega to the desired slip angle dependence to the stator current. Please contact siliXcon to get this value for your motor.

Limitations

• Please use only VECTOR algorithm. BLDC has no use for this type of motor.
• For the ACIM in FOC mode, sensorless mode is not supported at the moment. You need to provide a shaft sensor.