Closed manu-aesim closed 5 months ago
Root cause This is a bug.
In motor blocks, the initial speed (speed at t<0) is defined at 0 rpm internally. In the meantime, when connecting the constant speed load to a motor block, the motor speed does NOT ramp up gradually but rather starts at the specified speed from the first simulation step. As a result, the motor shaft torque at the first step was always showing physically unreasonable high value. E.g.: T_ag = Jdw/dt + Bw + T_shaft = J (w_now - w_prev)/(t_now - t_prev) + Bw +T_shaft
T_ag: Air gap torque (torque generated by the motor, scope value from a motor block) T_shaft: Shaft torque ("torque generated by the motor" - "torque used by motor inertia", torque probe value) J:Inertia, B: friction w: speed, t: time
In this bug, the component of (w_now - w_prev)/(t_now - t_prev) was causing physically unreasonable answer at the first step.
Solution Add an input field for the initial speed to motor blocks. (The same sense that the capacitance in SIMBA has a input filed for the initial voltage).
In some rare cases, when a PMSM shaft is connected to a constant speed load, the measured torque is not equal to the torque from the machine scope.