Variable frequency speed regulation has become the mainstream speed regulation scheme and can be widely used in continuously variable transmission in all walks of life. Especially with the increasing application of frequency converters in the field of industrial control, the use of vfd rated motor is also becoming more and more extensive. It can be said that due to the advantages of frequency conversion motors over ordinary motors in frequency conversion control It is not difficult to see the figure of the inverter motor. A variable frequency motor refers to a motor whose temperature rise will not exceed the rated allowable value of the motor under standard environmental conditions, with 100% of the rated load running continuously within the range of 10% to 100% of the rated speed.
Three-phase asynchronous motor is a type of motor powered by 380V three-phase AC power supply (phase difference of 120 degrees) at the same time. difference rate, so it is called a three-phase asynchronous motor. Three-phase asynchronous motors have high power and are mainly made into large motors. It is generally used in large industrial equipment with three-phase power. The first thing to note is that three-phase asynchronous motors are only used for motors, and rarely used as generators, and synchronous motors are used to generate electricity.
The variety of types of motors leads us to be confused when choosing a suitable motor, and analyze the difference between variable frequency motors and three-phase asynchronous motors. The biggest difference between the variable frequency motor and the three-phase asynchronous motor is that the cooling fan of the variable frequency motor such as the vfd synchronous motor is not fixed on the shaft of the motor and rotates synchronously with the motor, but is powered by the power frequency power supply alone. Even if the motor runs at a frequency of 5hz, the cooling fan still runs at 50Hz. RPM operation.
The three-phase asynchronous motor cooling fan is fixed on the shaft of the motor, and the speed is the same as that of the motor. When running at low frequency, the fan also runs at a low speed, the cooling capacity is greatly reduced, the heat generated by the motor cannot be dissipated, and the motor will be burned in severe cases. Also, the structure and withstand voltage of the frequency conversion motor have been specially designed and strengthened to adapt to the situation of high-speed and high-order harmonics. Some variable frequency motors do not use additional cooling fans, but increase the heat dissipation area on the surface of the motor to solve these problems.
Three-phase permanent magnet ac synchronous motor and variable frequency motor have their own characteristics. In order to select a motor more reasonably, a series of conditions should be based on the working mode, the actual working environment, and so on. Due to the mechanical structure of variable frequency motors, the design of electrical parameters is different from that of asynchronous motors. Therefore, it is necessary to reasonably select the required motor type.