The control method of synchronous motor and synchronous motor

The present invention provides a synchronous motor, the synchronous motor in the interior (5) has a three-phase inverter (3) and position sensors (9), in accordance with the input current detection circuit (12) for calculating the digital output of the analog input current value the unit (47), the input current detection circuit (12) detects the current flowing through the three-phase inverter input current DC input terminals, and also includes a digital feedback speed control unit (44) which regulates three-phase inverter output the size and frequency of the AC voltage, so that according to the position sensor (9) is output by the motor speed calculation unit (41) calculating a motor speed approaches the speed command value, the speed command value from said synchronous motor outside by the communication receiving unit (42 )receive. Further, in the synchronous motor having an internal communication transmission unit of the input current value and the speed of transmission to an external synchronous motor (43).