Effect of Rotor Structure on Performance of Permanent Magnet Synchronous Drive Motor
The permanent magnet synchronous drive motor can be divided into surface type and built-in rotor structure by the installation method of permanent magnet steel on the rotor. The surface rotor structure can be divided into surface mount type and embedded type. The built-in permanent magnet steel excitation direction can be divided into a radial rotor structure, a tangential rotor structure and a permanent magnet rotor structure integrating a radial and tangential hybrid magnetic circuit.
The surface-mounted rotor structure has the same d-axis and q-axis inductance, and the rotor does not have a salient pole effect, so no reluctance torque is generated. Since the permanent magnet steel is directly exposed to the air gap magnetic field, the permanent magnet steel is easily demagnetized, The weak magnetic capability is limited. In the embedded rotor structure, the q-axis inductance is greater than the d-axis inductance, and the rotor has a salient pole effect, so there is a reluctance torque.
The reluctance torque can effectively increase the power density of the motor. The dynamic performance of the embedded structure is improved compared with the surface mount type, but the magnetic flux leakage coefficient and manufacturing cost are both larger than the surface mount type. The permanent magnet steel with built-in rotor structure is located inside the rotor, and there is a pole piece made of ferromagnetic material between the outer surface of the permanent magnet steel and the inner circle of the stator core. Used to protect the permanent magnet steel in the built-in rotor core. Reluctance torque is generated due to the asymmetry of the rotor magnetic circuit structure. It helps to improve the overload capacity and power density of the permanent magnet synchronous drive motor. And easy to "weak magnetic" speed expansion.
The selection of a suitable rotor structure has an extremely important influence on the performance of the permanent magnet synchronous drive motor. Honda's Hybrid Prius (2003, 2004, 2010), 2007Ca唧 and 2008LS600h, Honda produces 2005Accord. The main drive motor uses a permanent magnet synchronous drive motor, but the rotor structure is not the same. Among them, 2005 Accord is a surface embedded structure, Prius, 2007 Camry and 2008 Ls600h are built-in structures, the 2003 Prius rotor structure is "one" type, 2004Prius, 2010Prius and 2007 Camry are "V" type. 2008Ls600h is a "triangular" structure, as shown in Figure 2, the main parameters are shown in Table 1.
Can be seen from Table 1. The 2004Prius, 2007CaII, 2010Prius and 2008Ls600h drive motors with built-in rotor structure have significantly improved maximum power, maximum speed and power density compared to the 2005Accord drive motor with surface rotor construction. And the different permanent magnet built-in structure also has a great influence on the parameters of the drive motor.
Based on the above discussion, the built-in rotor structure has good dynamic and steady-state performance, can provide high torque and high power, and has high power density. In addition, different structural types in the built-in rotor also have a greater impact on the permanent magnet synchronous drive motor. Therefore, research on the design of the built-in rotor structure is strengthened. Exploring the rotor structure with good economy and excellent performance is of great significance to improve the performance of permanent magnet synchronous drive motor.
