The NI 9502 provides support for either Trapezoidal commutation mode or Field Oriented Control commutation mode. The I/O nodes available for the module change depending on the Commutation Mode selected in the C Series Module Properties dialog box.

Trapezoidal Commutation

Trapezoidal commutation involves sending current through two of the three motor phases at any time. The phase transitions are controlled by the Hall effect sensor state changes. With trapezoidal commutation, one electrical revolution is divided into six steps of 60 degrees each.

The NI 9502 performs trapezoidal commutation based on the Hall effect sensor inputs. For proper phase switching to occur, the Hall sensors from the motor must be connected to the correct Hall inputs on the NI 9502 module. The Hall sensor phase sequence is motor-dependent, so selecting the correct inputs requires manual testing. Refer to Connecting Hall Effect Sensors for Trapezoidal Commutation for a detailed walkthrough using an example VI for assistance in determining the proper Hall input connections to the NI 9502 module.

The following figure shows the NI 9502 module block diagram when it is used in Trapezoidal commutation mode.

Figure 136. NI 9502 Block Diagram showing Trapezoidal Commutation Mode

If your application requires position feedback you can also use a different I/O module for encoder feedback as shown in the following figure.

Figure 137. NI 9502 Block Diagram showing Encoder Feedback

While trapezoidal commutation is simple to use, it does produce a torque ripple of up to 15% at slow speeds, which is not the case with Field Oriented Control commutation.

Field Oriented Control

Field Oriented Control (FOC) commutation mode uses a more advanced algorithm that allows smooth motion at slow speeds and better efficiency at high speeds. The LabVIEW NI SoftMotion Module Premium provides VIs and example programs that make it easier to use the NI 9502 with FOC commutation mode. LabVIEW Platform includes a free 30-day evaluation of the NI SoftMotion Module Premium that you can install to evaluate using the NI 9502 in FOC mode. The following figure shows an example motor phasing diagram during FOC mode.

Figure 138. Motor Phasing Diagram during FOC Mode

The following figure shows the NI 9502 module block diagram when it is used in FOC commutation mode.

Figure 139. NI 9502 Block Diagram showing FOC Commutation Mode