3 Practical Tips for Setting SmartTune Parameters

In many cases, the system level voltage and expected speed are usually different from those specified by the motor data sheet (or in some cases, users even do not have a data sheet). And therefore, the current value when motor is driven at this voltage and speed is unknown. If users randomly set the current value, fault can be triggered and motor cannot achieve the expected speed. This section introduces some tips for users about what to do when fault happens and how to set the proper current value.

First, the rated current parameter must be set less than motor drivers’ peak output current capability. This value can be found in the data sheet of motor driver. Also, the current limit of the external power supply needs to be higher than the current needed from the motor to avoid current clamping of the power supply.

Then, supposing your current setting is already less than motor driver’s peak output current, if one of the following situations occurs, this indicates that your current setting is still too high and you can reduce the current value a little bit and try again:

• SmartTune configuration failed and the fault monitor shows MPET_IPD_FAULT.

This indicates that the setting current value is so high that SmartTune fails to calculate motor parameters. To make sure this fault not happens, the current needs to also be less than V/R, where R is motor phase resistance.

• SmartTune configuration failed and the fault monitor shows CURRENT_LOOP_SATURATION.

This indicates that even if PWM duty is set to nearly 100%, the rated current still cannot be reached. Check the Voltage Magnitude in the Motor Status panel (if not shown, click on the Status Select and tick on this parameter), and you can see that Voltage Magnitude is nearly 100%.

If one of the following situations occurs, this indicates that your current setting is too low and you can increase the current value a little bit and try again:

• SmartTune configuration failed and the fault monitor shows MPET _BEMF_FAULT.

This indicates that before the speed level is not enough for SmartTune to detect BEMF and calculate BEMF constant.

• SmartTune configuration successful, but when you set the speed to 100% (maximum), the fault monitor keeps showing SPEED_LOOP_SATURATION.

This indicates that current is clamped before motor reaches rated speed. Check the Speed Feedback in the Motor Status panel (if not shown, click on the Status Select and tick on this parameter), and you can see that the Speed Feedback is less than Reference for Speed Loop. At this time, Voltage Magnitude is far less than 100%, so there is still margin for PWM duty but the current threshold has been reached.

If the following situation occurs, this indicates that the system voltage is not high enough to achieve the expected speed with SmartTune configuration, and you need to either increase the rated voltage or reduce the rated speed.

• SmartTune configuration successful, but when you set the speed to 100%, the fault monitor keeps showing both SPEED_LOOP_SATURATION and CURRENT_LOOP_SATURATION.

This indicates that PWM duty is set to nearly 100%, but both the rated current and the rated speed cannot be reached. Check the Voltage Magnitude and Speed Feedback in the Motor Status panel (if not shown, click on the Status Select and tick on this parameter), and you can see that Voltage Magnitude is nearly 100%, but the Speed Feedback speed is less than Reference for Speed Loop.

Figure 3-6 summarizes all the fault situations above and the tuning tips: