Speed regulation strategy of permanent magnet synchronous motor for electric vehicles
Permanent magnet synchronous motor, in 2016, the largest electric motor category in the country. Its growing success is mainly due to the cheapness of electronically controlled speed regulation and the significantly superior power density brought about by the simple structure.
1 working principle
Permanent magnet synchronous motor, the most basic composition of the stator and rotor. The stator is similar to an asynchronous motor rotor and is wound from insulated copper wire. The rotor contains permanent magnets and has a defined number of poles to establish the main magnetic field of the motor.
1.1 stator
The stator of the permanent magnet synchronous motor is the same as the asynchronous motor, and the three-phase windings are evenly arranged at an angle of 120°.
The characteristic parameters of the stator include the number of winding phases (generally single-phase, three-phase and multi-phase), and the number of winding slots.
The definition of the number of winding slots, half of the number of stator slots, divided by the product of the number of stator phases and the number of rotor poles. The permanent magnet motor can be divided into an integer slot winding and a fractional slot winding according to the number of winding coils accommodated in each stator slot.
Fractional slot windings mean that windings belonging to different phases may be placed in the same stator slot. Compared to the integer slot winding, the fractional slot winding has advantages in addition to the high insulation requirements.
The number of slots required to be excavated on the stator core is reduced, which saves space for the windings and simplifies the machining process; each slot accommodates a plurality of pole numbers, reducing the impact of excessive portions between the slots and the slots during operation. Vibration to improve the excitation waveform.
1.2 rotor
The rotor is the source of its own characteristics of permanent magnet synchronous motors. The permanent magnet rotor consists of two parts: the intimate and the permanent magnet.
Surface type
Depending on the position of the permanent magnets placed on the rotor, it can be divided into surface type, built-in type, hybrid type and claw pole type.
As the name suggests, the surface rotor is to attach the permanent magnet piece to the surface of the rotor; while the built-in type is to fix the permanent magnet inside the core. Hybrid is the combination of the previous two.
The surface and built-in types differ greatly in their arrangement, and the magnetic fields they generate are also very different. In the built-in rotor output power process, the torque includes a reluctance torque component in addition to the electromagnetic torque component. The permanent magnet synchronous motor with built-in rotor has obvious advantages in power density.
