Per Unit defination

Hello,

I am not sure what per unit means. In 2XDCMotor-setting.h file it defines Base_Voltage =66.32 and Base_Current=7.2Amp. I am driving DC Brushed motor rated @24VDC and 0.35Amp.

If I set Vref1=0.5 – what does it mean? I understand that positive and negative value change direction.

FYI-I am using 2XDC motor example using DRV 8412.