Controller for permanent magnet synchronous motor and motor control system

The invention provides a controller for permanent magnet synchronous motor and a motor control system. Two motor constants in the two zones such as a low-speed zone and a high-speed zone are defined. A motor control system includes: a permanent magnet synchronous motor; a power converter connected to the motor, a current detector configured to detect a current flowing through the permanent magnet synchronous motor, a controller generating a control signal for controlling the power converter; the controller comprising: a vector controller configured to generate the control signal on the basis of the detected current; an axial error estimating computing unit configured to estimate an axial error information which is a difference between a phase value of the motor and the phase estimation value obtained by integrating a rotational speed estimation value of the motor; a speed estimating computing unit, which is characterized in that: a motor constant identification computing unit configured to identify a motor constant of the permanent magnet synchronous motor with the q-axis voltage component and the rotational estimation value or a rotational speed command and reflects the identified motor constant in generating the control signal by the vector controller.