Due to the influence of a large number of harmonics and transient pulse voltage, the electromagnetic line will be damaged by the running variable frequency motor. Therefore, the insulation performance of electromagnetic wire is particularly important for the reliability of the insulation structure of variable frequency motor. Frequency conversion enamelled wire with corona resistance shall be used for frequency conversion motor.
 
Pulse resistant aluminum magnet wire is a special enamelled wire that can withstand corona and prolong the service life of variable frequency motor. It is mainly used for various variable frequency motors, speed regulating motors, lifting motors and elevator motors.

 
When IGBT-PWM frequency control equipment is powered, the power supply cannot be pure sine wave. The residual modulation pulse is applied to the motor end to form a high peak (high voltage peak), and the wave rise time is steep. In addition, the output voltage frequency may change or the frequency is very high, and the inevitable partial discharge and dielectric heating inside some motors will seriously damage the insulating film of the enameled wire. Use variable frequency motor. This greatly shortens the service life of enameled wire, so it is necessary to develop corona resistant enameled wire.
 
Description of variable frequency control terms
 
IGBT (insulated gate bipolar transistor) is a kind of insulated gate bipolar transistor. It is a composite fully controlled voltage driven power semiconductor device composed of BJT (bipolar triode) and MOS (insulated gate FET). It has the advantages of high MOSFET input impedance and reduced GTR switching voltage.
 
Pulse width modulation (PWM) is the abbreviation of "pulse width modulation". Using the digital output of microprocessor to control analog circuit is a very effective technology. It is widely used in many fields from measurement, communication to power control and conversion.
 
Practical experience sharing
 
For variable frequency motors with power less than 300kW, the electromagnetic wire manufacturer recommends the use of circular pulse resistant aluminum magnet wire. For the quality of round enamelled wire, special attention shall be paid to the heat resistance, softening breakdown, paint film continuity, dielectric loss curve, impulse voltage resistance and flexibility of electromagnetic wire. At present, special enamelled wires have been used in variable frequency motors in China. It is reported that their pulse withstand voltage is 200 times higher than Q (ZY / XX) - 2.
 
According to the particularity of variable frequency motor, the electromagnetic wire manufacturer pays special attention to the film thickness and uniformity of enameled wire of variable frequency motor. Generally speaking, polyimide film coated sintering line is used for variable frequency motors above 300kW. There are also polyimide film coated sintered wires specially used for variable frequency motors abroad. Similar coated sintering lines have been successfully developed in China. The practice shows that the inverter motor manufactured by the inverter electromagnetic wire is in good condition after leaving the factory.
 
Frequency conversion electromagnetic wire came into being
 
In recent years, the corona resistant enameled wire for AC variable frequency motor, pulse resistant aluminum magnet wire, has become a hot topic in the electromechanical industry and electromagnetic wire industry. China's AC variable frequency motor has been developed for many years, but as the main insulation material of variable frequency motor - corona resistant enamelled wire, it has been developed in China since 1998 and has been mass produced now.
 
European and American manufacturers who developed corona resistant enameled wires and coatings in the early stage mainly used titanium, chromium, silicon, aluminum and other metal oxide powders to fill the commonly used high temperature resistant enameled wires. When fully mixed, they will become pulse resistant aluminum magnet wire. These metal oxide powders are distributed between polymer molecules. When solvents are evaporated and dried and resins are crosslinked and cured, they are fixedly "embedded" in the middle of polymer molecules and act as a reinforcing agent of organic polymers. But the disadvantages are obvious.
 
With the improvement of electromagnetic wire manufacturers' products, the performance of frequency conversion electromagnetic wire coating has been significantly improved, especially for the current development of high-efficiency, ultra-high efficiency and ultra-high efficiency motors, which not only meets the requirements of anti corona, but also effectively improves the slot fullness of motor windings by reducing paint film.