For a system to experience electromagnetic compatibility (EMC) issues, three factors must be present: electromagnetic disturbance sources, coupling paths, and sensitive equipment. When encountering EMC problems, it is necessary to start with these three factors and prescribe the right remedy. By eliminating one of these factors, the EMC issue can be resolved. The electromagnetic disturbance source of the CNC power supply manufacturer in China is the high-frequency power switching circuit, which cannot be eliminated; the sensitive equipment is external and not controlled by the CNC power supply manufacturer in China; therefore, the most critical step is to cut off the coupling path. There are two ways for electromagnetic interference to be transmitted: conduction and radiation, and three methods to be used: shielding, filtering, and grounding.

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Various conductive materials are primarily utilized to manufacture various casings and connect them to the ground, in order to cut off the transmission pathways of electromagnetic noise formed by electrostatic coupling, inductive coupling, or alternating electromagnetic field coupling through space. Shielding can effectively suppress electromagnetic interference transmitted through space. The purpose of using shielding is twofold: one is to restrict the leakage of internal radiated electromagnetic energy out of the control area, and the other is to prevent external radiated electromagnetic energy from entering the internal control area. CNC power supply manufacturers in China use conductors such as aluminum or iron for full metal encapsulation to achieve the effect of shielding.

To reduce radiation interference on wires, magnetic rings are usually added to high-current wires and input/output wires, such as the connecting wires of filter inductors, to prevent the transmission of interference signals to the outside.

Isolation primarily employs devices such as relays, isolation transformers, or optoelectronic isolators to cut off the transmission path of electromagnetic noise in the form of conduction. Its characteristic is to separate the grounding systems of the two circuit parts, thereby eliminating the possibility of coupling through impedance.

filtering

The input and output interfaces of the CNC power supply manufacturer in China are designed with EMI filters, which aim to control EMI conducted interference and only allow ideal low-pass currents of DC and mains frequency to pass through. It also serves as a bidirectional filter, which can both prevent the CNC power supply manufacturer in China from emitting noise interference to the outside and suppress the introduction of external interference into the system. The filter includes X capacitors, Y capacitors, and common mode inductors. The common mode inductor consists of two windings with opposite directions and the same number of turns on the same magnetic ring, so that the magnetic fields generated when current flows through the windings superimpose in phase, presenting a large inductive reactance to the interference current, thereby suppressing common mode interference. The common mode capacitor directly introduces the common mode current to the ground without passing through the power grid.

grounding

Regardless of the method used to suppress EMI interference, static electricity must ultimately be discharged through grounding. Therefore, grounding is of utmost importance for CNC power supply manufacturers in China. Grounding includes earthing, signal grounding, etc. The design of the grounding body, the layout of ground wires, and the impedance of grounding wires at various frequencies not only involve the electrical safety of the product or system but also relate to electromagnetic compatibility and its measurement technology.

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