Solution to inverter interference problem

1.As soon as the inverter power supply of the heat exchange station is turned on,the pressure inverter power supply jumps randomly;
2.When using an inverter power supply to control water supply, the pressurechange is collected as a signal, and the pressure change is interfered by theinverter power supply; When the inverter power supply starts the motor, the voltage change signal isunstable and jumps violently;
4.After the inverter power supply is started, the voltage transformer (4-20mA)randomly jumps, but the nearby integrated thermal resistance (4-20mA) is notaffected, and the signal line is not shielded;
These phenomena are all caused by interference from the inverter power supply.

Why does inverter power generate interference?

Firstly, you need to know that an 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 through a rectification circuit and a smoothing circuit, and then converted into pulse voltage of different widths (called pulse width modulation voltage, PWM) through an inverter.. By using this PWM voltage to drive the motor, the torque and speed of the motor can be adjusted.
This working principle can cause three types of electromagnetic interference:
1.Harmonic interference
The rectifier circuit will generate harmonic current, which will cause voltage dropon the impedance of the power supply system, causing voltage waveformdistortion. This distorted voltage can interfere with many meters. The commonvoltage distortion is the top of the sine wave. Flatten. When the harmonic currentremains constant, the voltage distortion changes severely under weak powersupply conditions. The characteristic of this interference is that no matter how farthe device is from the inverter, it will cause interference to devices using the same power grid. 

2.RF conducted emission interference
Because the load voltage is pulse shaped, the current drawn by the inverter from thepower grid is also pulse shaped. This pulse current contains a large amount ofhigh-frequency components, causing radio frequency interference. Interference isindependent of the distance between the instrument and the inverter.
3.Radio frequency radiation interference
RF radiation interference comes from the input and output cables of the inverter powersupply. When there is RF interference current on the input and output cables of theinverter power supply, as the cables act as antennas, electromagnetic wave radiation willinevitably be generated, resulting in radiation interference. The PWM voltage transmittedon the inverter output cable also contains rich high-frequency components, which cangenerate electromagnetic wave radiation and cause radiation interference. Thecharacteristic of radiation interference is that when other electronic devices are close tothe inverter power supply, the interference phenomenon becomes severe.

How to solve the interference problem?

Methods for handling interference in inverter power sources
1.The inverter power supply should be grounded at a single point, preferably with a shortand thick wire;
2.The signal wire of the sensor is shielded with two feet, and the shielding layer isgrounded with a cable clamp.
3.Install a power filter, filter magnetic ring, or isolator on the power supply of the sensorfor isolation.
4.Suppress harmonics generated by inverters. Optional filtering products include: inverter input filter, inverter output filter, inverter input reactor, inverter output reactor, etc. Serializing reactors in the input circuit is an effective method to suppress low harmonic currents.
In addition, in order to prevent interference from the inverter power supply on the signal and control circuit, it is necessary to use separate isolated power supplies for controllers, instruments, and industrial computers.
In fact, the simplest method on site is:
Keep the instrument away from the inverter! But it's not always possible to eliminate interference, and methods still need to be tried one by one.