EGR pump system and control method of EGR pump

A method of operating an exhaust gas recirculation (EGR) pump for an internal combustion engine comprising:

• providing an EGR pump assembly including an electric motor coupled to a roots device having rotors, the EGR pump assembly operably connected to the internal combustion engine;
• providing a system controller;
• providing an EGR control unit linked to the EGR pump assembly;
• sending a speed command from the system controller to the EGR control unit defining a speed set point;
• determining if the electric motor is in a regeneration state;
• determining if the electric motor is outputting maximum torque;
• determining if an actual speed is greater than an over speed limit;
• outputting an over speed warning if the motor is outputting maximum torque in the regeneration state or if the actual speed is greater than the over speed limit;
• and
• outputting a current to the electric motor maintaining the speed set point and regulating an EGR mass flow rate.