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Frequency conversion and pole-changing speed regulation are two completely different speed regulation methods for motor products. Pole-changing speed regulation can only realize multiple speed gears of the same motor, and the corresponding gears correspond to constant speed; while variable-frequency speed regulation can realize smooth transition or the soft start of motor speed with a certain number of poles, which can make the motor run stably at any speed.
The permanent magnet synchronous motor also uses frequency conversion technology to realize the soft speed regulation of the motor, and can automatically adjust the motor speed according to the actual demand of the load to achieve the purpose of energy-saving.
Permanent magnet synchronous motor and asynchronous variable frequency motor have one thing in common, that is, inverter power supply. Due to the power supply of the inverter, the permanent magnet synchronous motor can realize the functions of soft start and variable frequency operation, but the software control method of the inverter is different. Some inverter manufacturers have also introduced inverters for permanent magnet motors with better performance.
Permanent magnet synchronous motors are divided into self-starting permanent magnet synchronous motors and variable frequency speed-regulating permanent magnet synchronous motors according to the starting method. Self-starting permanent magnet synchronous motors generally use high-performance rare earth permanent magnet materials and have asynchronous starting squirrel cages in the rotor structure. It can be used directly by power frequency power, running at a fixed speed, or can be powered by a frequency converter for speed regulation. The rotor of the variable frequency speed-regulated permanent magnet synchronous motor has no windings or starts the squirrel cage, and cannot start automatically. It must be driven by a special frequency converter. In theory, the rotor does not heat up and has no loss, and the energy-saving effect is extremely good.
In view of the above, how to choose a permanent magnet synchronous motor? It is recommended to carry out according to the actual supporting equipment and working conditions: to directly replace ordinary motors, self-starting permanent magnet synchronous motors should be used; for fans and pumps that do not require high starting torque and mainly achieve energy saving through speed regulation, self-starting can be used. The permanent magnet synchronous motor replaces the variable frequency asynchronous motor and also improves the motor performance by changing the frequency conversion parameter modulation ratio or carrier ratio, which can achieve a better energy-saving effect; equipment that requires a wide range of speed regulation (that is, broadband work requirements) and high power density, Only use variable frequency speed regulation permanent magnet synchronous motor.
The self-starting permanent magnet synchronous motor was applied earlier. In the era when the frequency conversion technology was not very mature, the self-starting permanent magnet synchronous motor was used on the low-power industrial equipment, and the power supply was directly supplied by the power frequency grid, which achieved a significant effect of energy-saving compared with the general asynchronous motor.
From the analysis of the overall demand for energy-saving and speed regulation, the permanent magnet synchronous motor with variable frequency speed regulation will become the new favorite of the era. As the frequency conversion technology becomes more and more popular, the frequency conversion speed regulation permanent magnet synchronous motor will gradually replace the most widely used asynchronous motor and enter all walks of life.
