The IM motor is an induction motor, also known as an "asynchronous motor". It is a device that places the rotor in a rotating magnetic field and obtains a rotating torque under the action of the rotating magnetic field, so that the rotor rotates.
PM motor is a permanent magnet synchronous motor, which is a synchronous motor that generates a synchronous rotating magnetic field by permanent magnet excitation.
1. The average efficiency is different
The excitation magnetic field of the permanent magnet synchronous motor is provided by the permanent magnet, the rotor does not need excitation current, and the efficiency of the motor is improved;
The induction motor cannot reach any speed point to save electric energy, so the efficiency is low.
2. The working principle is different
The permanent magnet in the permanent magnet synchronous motor is used as the rotor to generate a rotating magnetic field. The three-phase stator winding reacts through the armature under the action of the rotating magnetic field to induce a three-phase symmetrical current. At this time, the kinetic energy of the rotor is converted into electrical energy, and the permanent magnet synchronous motor is used as a generator. . When three-phase symmetrical current is applied to the stator side, since the three-phase stator has a difference of 120 in space, the three-phase stator current generates a rotating magnetic field in space, and the rotor is moved by electromagnetic force in the rotating magnetic field. At this time, electrical energy is converted into kinetic energy. Permanent magnet synchronous motors are used as motors.
The induction motor uses the relative movement between the rotating magnetic field generated by the stator (its speed is the synchronous speed n1) and the rotor winding, and the rotor winding cuts the magnetic line of induction to generate an induced electromotive force, thereby causing an induced current in the rotor winding. The induced current in the rotor winding interacts with the magnetic field to generate electromagnetic torque, which makes the rotor rotate. As the rotor speed gradually approaches the synchronous speed, the induced current gradually decreases, and the generated electromagnetic torque is also reduced accordingly. When the asynchronous motor is working in the motor state, the rotor speed is less than the synchronous speed.
3. Different volume and weight
The permanent magnet synchronous motor uses high-performance permanent magnet materials to provide the magnetic field, so that the air gap magnetic field of the permanent magnet motor is larger than that of the induction motor. The volume and weight of the permanent magnet motor can be greatly reduced compared with the induction motor.
The induction motor is composed of a stator, a rotor, and a bearing. The stator is mainly composed of an iron core, a three-phase winding, a base, and an end cover. Therefore, the volume and weight are relatively large.