I have read that a VFD operaing in an open loop V/Hz, or Sensorless vector control mode has trouble detecting atctual speed at low speeds due to slip errors. I belive I have seen that somewhere below 5Hz or so the motor cannot acurately manage speed or torque due to errors in calculating motor slip speed. I believe this has something to do with the fact that in open loop control because there is about a 2% of base speed error in calculating the actual slip speed.
Can someone explain to me why with decreasing speed the slip error increases? Why below 5Hz can the motor not manage torque and speed as mentioned above?
I know that torque in an induction motor is produced by the interaction between the rotor induced voltage and its field Bnet and the rotor field resulting from the rotor current Br. As the motor becomes more loaded the angle between Bnet and Br increases and thus the torque increases. Does this interaction between Bnet and Br have something to do with how the VFD detects slip error?
Can someone explain to me why with decreasing speed the slip error increases? Why below 5Hz can the motor not manage torque and speed as mentioned above?
I know that torque in an induction motor is produced by the interaction between the rotor induced voltage and its field Bnet and the rotor field resulting from the rotor current Br. As the motor becomes more loaded the angle between Bnet and Br increases and thus the torque increases. Does this interaction between Bnet and Br have something to do with how the VFD detects slip error?
