Generally, the motor is planned according to constant frequency and constant voltage. It is impossible to be completely accustomed to the requirements of inverter speed regulation, so it cannot be used as a variable frequency motor. 1. The impact of the inverter on the motor is mainly due to the power and temperature rise of the motor. The inverter can generate different levels of harmonic voltages and currents during operation, so that the motor runs at non-sinusoidal voltage and current. The higher harmonics inside will Causes motor stator copper loss, rotor copper loss, iron loss, and additional loss addition. The most significant is rotor copper loss. These losses will cause the motor to generate additional heat, reduce power, and reduce output power. Generally, the temperature rise of the motor is generally increased by 10%. -20%. 2. Insulation strength of the motor The carrier frequency of the inverter ranges from several thousand to more than ten kilohertz, so that the stator winding of the motor must accept a very high rate of voltage rise, which is equivalent to applying a steep shock voltage to the motor, causing the motor to turn Insulation is more severely tested. 3. Harmonic electromagnetic noise and sensation Generally, when the inverter is powered by an electric motor, the sensation and noise caused by electromagnetic, mechanical, ventilation and other factors will become more chaotic. The various harmonics contained in the variable frequency power supply and the inherent space harmonics of the electromagnetic part of the motor interact with each other to form various electromagnetic excitation forces, fan system and then increase the noise. Because the operating frequency scale of the motor is wide and the rotation speed is large, the frequency of various electromagnetic force waves is difficult to avoid the natural oscillation frequency of each structural part of the motor. 4.

Cooling problem at low speed When the frequency of the power supply is low, the losses caused by higher harmonics in the power supply are large; secondly, when the speed of the motor is reduced, the cooling air volume decreases in proportion to the third power of the speed, causing the motor If the heat is not emitted, the temperature rise increases sharply, and it is difficult to achieve constant torque output. Differences between general motors and variable frequency motors 1. The insulation level is higher. Generally, the insulation level of variable frequency motors is F level or higher. It is necessary to strengthen the insulation strength to the ground and the turns, especially considering the ability of the insulation to withstand voltage. 2. Frequency converter motors have higher requirements for oscillation and noise. Frequency converter motors must fully consider the stiffness of the motor components and the whole, and strive to improve its natural frequency to avoid resonance with various force waves. 3. Different cooling methods for variable frequency motors Generally, forced ventilation cooling is used for variable frequency motors, that is, the main motor cooling fan is driven by an independent motor. 4. Different protection methods require https://www.chinakxdq.com/product/fan-system/fan-system.html

bearing insulation methods for variable frequency motors with a capacity exceeding 160KW. The main reason is that the asymmetry of the magnetic circuit is prone to occur, and the shaft current will also occur. When the currents generated by other high-frequency weights are combined together, the shaft current will be greatly added, and then the bearing will be damaged, so the insulation method is generally adopted. For constant power variable frequency motor, when the speed exceeds 3000 / min, special high temperature resistant grease should be selected to compensate for the temperature rise of the bearing. 5. Different heat dissipation system The cooling fan of the variable frequency motor is powered by an independent power supply to ensure continued heat dissipation.