The most fundamental difference between a variable frequency motor and a commercial frequency motor is the difference in the power supply of the two. The input voltage and frequency of the commercial frequency motor are relatively constant, while the input voltage and frequency of the variable frequency motor are variable, which is because This factor is destined to be relatively harsh in the operating conditions of the variable frequency motor. Therefore, necessary measures must be taken for the relevant links of the motor body to prevent quality problems during the operation of the motor.
The frequency conversion motor is powered by the frequency converter, and the output of the frequency converter is a rectangular wave with a non-sinusoidal waveform. The high-order harmonics generated by the frequency converter have a great influence on the performance of the motor. The high-order harmonics will cause copper loss in the motor stator and rotor copper. The most significant increase in power consumption, iron loss and additional loss is rotor copper loss. Due to the increase in losses, the most direct consequence is the increase in the temperature of the motor.
In view of the above reasons, there are some differences between the winding insulation structure of the inverter motor and the industrial frequency motor: the insulation level of the inverter motor is at least one level higher than that of the ordinary motor. Class F insulation design, in addition to the difference in insulation materials, the corresponding magnet wires will also be different:
(1) The heat-resistance grade of the magnet wire for variable frequency motor should match the insulation structure of the winding, and it should be selected according to the grade no less than 155.
(2) Electromagnetic wires for frequency conversion motors should be dedicated electromagnetic wires. The difference between this type of electromagnetic wires and ordinary electromagnetic wires is the particularity of the insulating paint, which can avoid the phenomenon of discharge and heating of the insulating medium, and can effectively ensure the safe operation of the frequency conversion motor. Extend the service life of the motor.
In practical applications, some motor manufacturers use thick varnished electromagnetic wires on the variable-frequency motor windings, which can effectively alleviate the causes of winding failures, but they cannot fundamentally solve the problem. Therefore, from the analysis of the essential characteristics of the variable frequency motor, the use of a special variable frequency electromagnetic wire can effectively solve the heat resistance and prevent the occurrence of corona problems.