1. Introduction The use of frequency converters for speed control of AC induction asynchronous motors represents a revolutionary technological advancement in the field of electrical drives in the 20th century. With the widespread application of frequency converters, they have increasingly become the largest source of electromagnetic pollution in factory automation. It is common to see dozens or even hundreds of frequency converters installed in a single equipment-intensive factory. The nonlinear equivalent load of the DC-AC inverter in frequency converters causes them to not only pollute the factory power supply system in many system integration projects but also directly interfere with automation projects, leading to inaccuracies and malfunctions in the measurement and control system, severely damaging the stability of the large system, and even causing "bootstrapping" speed control failures due to interference with the frequency converter itself. Although international standards have strict specifications for EMC (IEC 61000 series electromagnetic compatibility design) of electrical equipment, and the China National Quality and Technical Supervision Bureau has decided to adopt them "equivalently" in China, and the Chinese national standard for power quality and harmonics in public power grids GB/T 14549-93 has been in effect for 14 years, the rapid development of China's economy and technology makes the pollution control of power electronic switching devices an urgent matter. The author of this article comes from the front line of automation integration engineering. In recent years, we have frequently encountered inverter interference problems in customer service, causing equipment malfunctions and halting factory production lines. Furthermore, locating the cause of these problems is quite difficult. After consulting relevant materials and combining this with my experience in handling such issues, I will discuss the sources and propagation methods of inverter interference, as well as some solutions for different interference situations encountered in practical applications. This aims to avoid the dogmatic approach of textbooks. 2. Inverter Interference Analysis Inverter interference problems generally fall into three categories: interference from the inverter itself; interference from electromagnetic waves generated by external equipment; and interference from the inverter to other low-voltage equipment. The inverter itself is a source of interference. As is well known, an inverter consists of two main parts: the main circuit and the control circuit. The main circuit of the inverter mainly consists of a rectifier circuit, an inverter circuit, and a control circuit. The rectifier circuit and the inverter circuit are composed of power electronic devices. Power and electronic devices have nonlinear characteristics. When the inverter is running, it performs rapid switching actions, thus generating high-order harmonics. Therefore, the inverter output waveform contains a large number of high-order harmonics in addition to the fundamental frequency. Regardless of the type of interference, high-order harmonics are the main cause of interference in frequency converters. The frequency converter itself is a source of harmonic interference, thus affecting equipment on both the power supply and output sides. Compared to the main circuit, the control circuit of the frequency converter is a low-energy, weak-signal circuit, making it highly susceptible to interference from other devices. Therefore, anti-interference measures must be taken for the control circuit during the installation and use of the frequency converter. 3. Analysis and Handling of Frequency Converter Interference Cases 3.1 How to Determine if a Frequency Converter is Experiencing Interference Problems Interference problems in frequency converters are mainly reflected in the operation of the motor. For example, the motor may suddenly stop during operation, run at varying speeds, or have unstable operating speeds. Other issues include the motor failing to stop, buttons not functioning, etc. These are all manifestations of interference affecting the frequency converter. 3.2 The general approach to handling grounding interference issues using the third method is to ensure good grounding. The general requirements for grounding terminals are: grounding terminals should be grounded using the "third method" (separate grounding); the grounding wire should be as short as possible and must be well grounded; shielded wires should be used for control return lines, with the far end of the shield suspended and the near end grounded; wiring should be done reasonably according to product requirements, separating high-voltage and low-voltage wires and maintaining a certain distance; avoid parallel wiring of inverter power lines and signal lines, and instead use distributed wiring; add anti-wireless interference filters, inverter input and output anti-interference filters or reactors; take shielding measures to prevent electromagnetic induction, even shielding the inverter with a metal box; appropriately reduce the carrier frequency; if communication functions are used, use twisted-pair cable for RS485 communication lines. Below, I will provide specific analyses of different interference situations in actual use. 3.3 In a three-phase five-wire power supply, a situation was encountered where the frequency converter kept running, and pressing the stop button had no effect. Inspection revealed that the frequency converter's ground wire was only connected to the transformer's neutral wire, while the transformer's neutral wire was not connected to the earth. Grounding the transformer's neutral wire restored the frequency converter to normal operation. Many small factories today generally neglect ground wire connections. When machine tools leave the factory, according to national electrical engineering standards, the ground wire and neutral wire are strictly separated. The neutral wire in the distribution cabinet has a dedicated terminal, and the ground wire has a dedicated grounding screw. Because this user had three phase wires and one neutral wire coming from the transformer, and only connected the neutral wire to the "N" terminal, while the ground wire was not connected, even though the control line used shielded wire and the shielding layer was connected to the grounding screw, it was not connected to the earth and therefore did not provide shielding. This caused the frequency converter to malfunction due to interference, and the motor could not stop. Connecting the neutral wire and ground wire in the distribution cabinet restored normal operation. Alternatively, the ground wire in the distribution cabinet can be directly connected to the earth. Many users connect the ground wire to the neutral wire, but this method has drawbacks. If the neutral wire is disconnected, starting a certain action of the machine tool may cause the machine tool to become electrified, posing a safety threat to personnel. This interference belongs to the type of interference of the frequency converter itself. 3.4 Case of interference of external equipment to frequency converter (1) Phenomenon. The motor occasionally fails to stop. After inspection, the shielding layer is grounded correctly and well. Lowering the carrier frequency has no effect. Adding magnetic ring filters to the input and output sides of the frequency converter has no effect. (2) Analysis. The distribution cabinet where the frequency converter is installed is too close to the power distribution room. A large current flows through the distribution cabinet in the distribution room. There is a strong magnetic field around the current, which interferes with the normal operation of the frequency converter. After moving the distribution cabinet away from the power distribution room, it returns to normal. This belongs to the interference of external equipment to frequency converter. 3.5 Case of interference of frequency converter to external equipment (1) Phenomenon. After starting the frequency converter, the motor does not move. (2) Analysis. The inverter's operating frequency is given by an external 4-20mA DC signal, which is input through a transmitter. The display shows a frequency of 0.00. Measuring the transmitter's output with an ammeter reveals no output. After connecting a 102 capacitor in parallel to the transmitter's output terminal and restarting, the equipment returned to normal, indicating that the signal source was interfered with. In engineering practice, a simple parallel capacitor connection to a signal line is a frequently effective and practical method for solving major problems. This is an example of inverter interference with external equipment. 4. Conclusion With the rapid development of industrial automation, the use of inverters is becoming increasingly widespread, and inverter interference problems are becoming more frequent. Many end-users often don't know how to solve this problem. This article aims to provide some assistance.