1.3 working process of permanent magnet synchronous motor
Permanent magnet synchronous motor, the stator is energized, and the stator winding becomes a group of electromagnets. The N pole and S pole of the electromagnet are evenly distributed along the inner side of the stator. The permanent magnet rotor itself has a stable N pole and S pole. There is an electromagnetic force between the stator and the rotor.
When the stator magnetic field rotates at a certain speed, the electromagnetic force pulls the rotor, follows the movement of the magnetic field, and tries to maintain the tendency to synchronize with the magnetic field.
1.3.1 Motor working mode
When there is a system load at the rotor shaft end, the system needs the motor to pull the rotor to rotate by the force of the stator magnetic field, so that the electric energy in the system works and is converted into mechanical energy. The rotor and stator are in the opposite positions as shown in the figure below.
At the instant shown in the figure, a pair of magnetic poles on the stator magnetic field rotate toward the left hand side of the reader. The rotor is pulled by the electromagnetic force of the stator and also moves to the left. The stator is in front and the rotor is in the back.
Thus, the direction of motion of the rotor forms an angle with the line of action of the electromagnetic force between the stator and the rotor, which is called the moment angle.
The moment angle is between 0 and 90° and the motor is in motor operating mode.
1.3.2 Generator working mode
When the rotor is pulled by the external mechanical force, it is in a rotating state, and the stator circuit is unobstructed, but the power is not connected.
The rotor rotates to form a rotating magnetic field, causing the stationary stator coil to passively cut the magnetic lines of force to generate an induced current. At this time, the stator and the rotor are in the relative positions shown in the following figure.
At the instant shown in the figure, a pair of magnetic poles on the permanent magnet rotor move toward the left hand side of the reader. The induced current generated by the stator acts as an electromagnetic force between the rotor. The direction of the line of action of the electromagnetic force is at an angle to the direction of motion of the rotor, ie the moment angle.
The value of the moment angle is between 90 and 180 degrees, and the motor is in the generator working mode.
1.3.3 reactive power working mode
The stator continues to pass a fixed frequency sinusoidal current. The rotor rotates synchronously with the magnetic field under the action of a rotating magnetic field. The rotor does not have any load torque. The rotor and stator are in opposite positions in the figure below.
