1. Electrical cabinet connected to the external 220V power supply line handling precautions
High-power equipment will cause serious pollution of the power grid, so that the grid voltage is a substantial rise and fall, surge. Due to the use of high-voltage
(220V), high internal resistance grid in our country, the grid is seriously polluted. Although the system uses voltage stabilization measures, but the grid noise will still run into the system. According to statistics, the power supply of the instantaneous short circuit, undervoltage, overvoltage, and the grid into the noise caused by CPU malfunction and data loss accounted for more than 90% of the interference, so in the anti-jamming design, the power supply should focus on the consideration of interference. Mainly pay attention to the following points:
1) The power line should be far away from any other cables in the system, and should be installed near the entrance of the filter, to ensure that the interference of the external power supply network into the cabinet;
2) Filter should be installed as close as possible to the power input socket, the incoming and outgoing wires close to the ground wiring, the two must be separated from the wires, can not be parallel to the wires, it is best to be 180 °, and the filter output of the output line is close to the ground, and the filter should be installed at the same time. 180 °, and the filter output power line to be far from the filter input power line, do not let them have the opportunity to close together, otherwise the interference has the opportunity to re-coupled to the power line;
3) Important components such as the AC power supply of the CNC system should be used to reduce the industrial frequency power supply of the low-pass filter, the high-frequency interference signals. If possible, CNC system within the servo motor drive, frequency converter, computer and control circuit power supply can be used separately 3 filters, so that not only can inhibit the external power interference, but also inhibit the mutual interference between the various parts. But be sure to pay attention to the above point 2, the filter output and input lines must be clearly divided, otherwise the filter may not be useful.
4) Pay attention to the alignment of the control cabinet, strong signal lines and weak signal lines should not be in a trunk line, and do not get too close.
2. Grounding and shielding considerations
Good grounding can effectively change the interference conduction path, lagoon into the control cabinet or a large piece of metal plane to go, so as to protect sensitive equipment from being affected. However, incorrect grounding locations and methods not only fail to protect circuits, but may introduce interference into sensitive equipment, resulting in a worse situation than before. Shielding, on the other hand, is to protect the internal circuitry so that interference is conducted through the shield to the earth, so the shield grounding is very important, requiring the shielding layer and the ground for the face lap to reduce impedance. The following are considerations for grounding and shielding:
1) The electrical control cabinet should be made of conductive sheet metal, and in order to ensure the electromagnetic consistency of the control cabinet, it should be one-piece construction or welding.
2) The mounting plate of the control cabinet is made of conductive metal plate to improve the grounding performance of the system.
3) The housings of strong electrical equipment such as filters, inverters, switching power supplies, motor drives, etc., are mounted on a metal plate that fits snugly.
4) At the entrance of each shielded cable into the control cabinet, the shield should be grounded.