Third, permanent magnet synchronous motor and synchronous motor
The working principle of permanent magnet synchronous motor and synchronous motor is the same. The difference is that permanent magnet synchronous motor is excited by permanent magnet, no excitation winding, no excitation loss; synchronous motor is electric excitation, excitation winding loss and heating are often ventilation and heat dissipation system. weakness.
Compared with synchronous motors and asynchronous motors, permanent magnet synchronous motors do not have electrical excitation and corresponding losses. The permanent magnet rotor does not generate heat, and the electrical load can be selected very high, so the volume is small and the power density is high. With the new motor control theory and the rapid development of rare earth permanent magnet materials, the performance of permanent magnet synchronous motors can be further improved, and there are many unique advantages compared with ordinary motors. Such as:
Energy efficient. Since the excitation magnetic field is provided by the permanent magnet, the permanent magnet rotor does not need to be excited, and the efficiency can be as high as 90% or more. Compared with asynchronous motors, the high-efficiency operating speed range is wide and energy saving is remarkable. Especially at low speeds, the advantages are even more pronounced.
The temperature rise is low. No electric excitation means no loss of heat, so the permanent magnet motor generally has a low temperature rise.
Good starting performance. The self-starting permanent magnet synchronous motor generally adopts an asynchronous starting mode. The permanent magnet synchronous motor rotor winding does not work during normal operation, and the permanent magnet motor rotor winding can be designed to fully meet the requirements of high starting torque, such as the starting torque multiple is increased from 1.8 times to 2.5 times or more.
Impact on grid operation. Asynchronous motors need to absorb a large amount of reactive current from the power grid, causing a large amount of reactive current in the power transmission and transformation system of the power grid, which in turn reduces the quality factor of the power grid and increases the load on power transmission and transformation equipment and power generation equipment. At the same time, the reactive current consumes part of the electric energy in the power grid, that is, the power transmission and transformation system, resulting in low efficiency of the power grid operation, and then the efficiency of the asynchronous motor is low, and the energy absorption from the power grid is superimposed. The electric energy loss is intensified, and the power grid load is increased. The hair is aggravated.
The unique advantage of the permanent magnet motor rotor without electric excitation and high power factor helps to improve the quality factor of the power grid or eliminate the need to install a compensator in the power grid.
Permanent magnet motors have a wide range of high-efficiency operation and are widely used in new energy vehicles.
Small size and light weight. The application of high-performance super-strong permanent magnet materials has greatly reduced the volume and weight of permanent magnet motors, and the power density is at least 1.5 times that of ordinary three-phase asynchronous motors.
