What's the use of switching frequency of converter?
The chopper device also has switching life, the higher the switching frequency, the shorter the life of the inverter, and will reduce the inverter output current and power. The smaller the chopping frequency, the higher harmonic content and the more serious harmonic pollution.
Switching frequency is generally the default value of the system is better, do not recommend any adjustments, generally only when problems are encountered, will be adjusted, because:The higher the switching frequency of the converter, the smoother the output waveform; the lower the switching frequency of the converter, the worse the output waveform. Switching frequency, to put it bluntly, is chopping, assuming we cut the sine wave for 100 and 1000, and that must be the combination of 1000 segments, the waveform is more like a sine wave, this should be understandable.
Very important！The higher the switching frequency is, the smaller the harmonic is when the output waveform passes through the motor winding. The reason is that the higher the switching frequency is, the higher the harmonic frequency is, the higher the harmonic impedance is, and the smaller the harmonic current is. The smaller the harmonic current is, the smaller the harmonic loss is and the smaller the torque ripple is, the better the motor performance is.However, the higher the switching frequency, the greater the frequency converter loss, the lower the efficiency of the inverter, and more importantly, the greater the heat, the inverter may not be able to bear.In addition, according to the fundamental frequency of operation, the switching frequency is preferably an integer multiple of the fundamental frequency, and this multiple is an integer multiple of 3, which can effectively reduce the low harmonics which affect the motor greatly!
Meanwhile, the switching frequency of the converter is adjusted, and the power loss can be adjusted. Because the switching frequency of power loss and inverter power module IGBT is related with the increase in switching frequency inverter and increasing the power loss, this makes the efficiency drop, two is the power module heating increases, is detrimental to the operation, of course work electric converter pressure is high, the power loss also increase effect.
By adjusting the switching frequency, system noise can be minimized, waveform smoothing is the best, and interference is minimal. Because the frequency converter mostly adopts the form of PWM modulation to carry out the frequency converter. That is, the output voltage of the inverter is actually a series of pulses, and the pulse widths and intervals are not equal. The size depends on the intersection point of modulation wave and carrier, that is, the switching frequency. The higher the switching frequency, the more the number of pulses in a cycle, the better the smoothness of the current waveform, but the interference to other devices is also greater. The lower the carrier frequency or the bad set, the motor will make unpleasant noise.
