Problem

Steps

• Before starting the configuration of the shunt resistor in the MotionLab software, it is assumed that the resistor has already been properly dimensioned in terms of its resistance and rated/peak power. If that is not the case, proceed to use the guidelines in the following article to size up the appropriate shunt resistor for your application: Dimensioning a shunt resistor for regenerative braking.
  
• Once sized up, we need to proceed to configure the shunt configuration parameters. The first one, its availability, is easily configured in the Actuator window by selecting "Yes" in the Shunt available field:
  

• The other 2 parameters can be easily configured as well in the Shunt window that appears once you set "Yes" to its availability. In order to understand better how these 2 parameters work, it is good to explain how the algorithm of the shunt works:
  

• As it can be seen from the picture, the external shunt is activated when the actual bus voltage is higher than Max user voltage plus hysteresis and is deactivated when the bus voltage is lower than Max user voltage hysteresis. The hysteresis is expressed as a percentage of max bus voltage.
  
• The duty used parameter has a range of 0 to 2048 with 0 meaning 0% of the duty cycle of the resistor is being used and 2048 meaning 100% of the duty cycle is used. For hysteresis a value of 1-2% is usually the best:
  

• Finally, you need to set the voltage level above which the shunt will start to operate. This can be done by setting the appropriate max user voltage in the Protections window, stated as "Over voltage warning level" in this window: