Why does the inverter power supply interfere?

First of all, we must know that the inverter power supply is used to change the frequency. The inverter includes a rectifier circuit and an inverter circuit. The input AC power is converted into DC voltage by the smoothing circuit of the rectifier circuit.

Then, the DC voltage is converted into pulse voltages of different widths (called pulse width modulation voltage, PWM) through the inverter. The essence is to use this PWM voltage to drive the motor to adjust the torque and speed of the motor.
This working principle causes the following three types of electromagnetic interference:

1. Harmony Interference
The rectifier circuit will generate harmonic currents. This harmonic current creates a voltage drop across the impedance of the power system, resulting in a distorted voltage waveform. Many instruments can be disturbed by this distortion voltage. A common voltage distortion is the top of a sine wave. flatten. When the harmonic current is constant, the voltage distortion is more serious when the weak current is supplied. This disturbance manifests itself as disturbance to equipment using the same power grid, regardless of the distance between the equipment and the inverter.

2. Radio frequency transmission emission interference
Because the load voltage is pulsed, the conversion from the grid is also pulsed from the grid. This pulsed current contains a lot of high-frequency components, resulting in radio frequency interference. The interference has nothing to do with the distance between the instrument and the inverter power supply.

3. Radio frequency radiation interference
Radio frequency radiation interference comes from the input and output cables of the inverter power supply. When there is radio frequency interference current on the input and output cables of the inverter power supply, since the cable is equivalent to an antenna, electromagnetic wave radiation will inevitably be generated and radiation interference will occur.

The PWM voltage transmitted on the output cable of the inverter is also rich in high-frequency components, which will generate electromagnetic wave radiation and cause radiation interference. The characteristic of radiated interference is that when other electronic devices are close to the inverter, the interference phenomenon becomes serious.