Precautions for Wiring of Electrical Control Cabinet of Machine Tool

The layout and wiring inside the electrical control cabinet is very important. A good layout and wiring is not only convenient for production and maintenance, but also can improve the reliability of the CNC system.
1. Precautions for handling the 220V power supply line outside the electrical cabinet
High-power equipment will cause serious pollution to the power grid, causing large fluctuations and surges in the power grid voltage. Since my country adopts high voltage
(220V) and high internal resistance power grid, the power grid is seriously polluted. Although the system has adopted voltage stabilization measures, grid noise will still enter the system. According to statistics, CPU malfunction and data loss caused by instantaneous short circuit, undervoltage, overvoltage of the power supply and noise from the power grid account for more than 90% of all kinds of interference. Therefore, in the anti-interference design, power supply interference should be considered. Mainly pay attention to the following points:
1) The power line should be far away from any other cables in the system, and a filter should be installed near the entrance to ensure that the interference on the external power supply
network enters the cabinet;

External 220V power line handling method

Picture 1 Treatment method of external 220V power line The difference is 180°, and the power line of the filter output should be far away from the power line of the filter input. Don’t let them have a chance to get closer together, otherwise the interference will have a chance to re-couple to the power line;

Figure 2 The input and output of the filter should not be too close
3) The AC power supply of important components such as the CNC system should use a low-pass filter to reduce the high frequency on the industrial frequency power supply. frequency interference signal. If conditions permit, three filters can be used for the power supply of the servo motor driver, frequency converter, computer and control circuit inside the CNC system, which can not only suppress the interference of the external power supply, but also suppress the mutual interference between the various parts. But be sure to pay attention to the second point above, the filter output and input lines must be clearly distinguished, otherwise the filter may be useless.
Figure 3 important equipment All power supplies are filtered by filters
4) Pay attention to the wiring in the control cabinet, strong current signal lines and weak current signal lines should not be routed in the same wire slot, and should not be too close together.

<IMG style="WIDTH: 600px; HEIGHT: 245px" alt=Strong and weak signal lines should be separated src=" 4 Strong and weak signal lines should be separated
2. Grounding and shielding precautions
Good grounding can effectively change the conduction path of interference and release it to the control cabinet or large out of the metal plane of the block, thus protecting sensitive equipment from being affected. However, the wrong grounding position and method will not only fail to protect the circuit well, but may introduce interference into sensitive equipment, resulting in worse than before treatment. Shielding is to protect the internal circuit, so that the interference is transmitted to the earth through the shielding layer, so the grounding of the shielding layer is very important, and the shielding layer and the grounding layer are requiredCarry out face-to-face bonding to reduce impedance. The following are the precautions for grounding and shielding:
1) The electrical control cabinet should be made of conductive metal plates. In order to ensure the electromagnetic consistency of the control cabinet, it should adopt an integral structure or welding.
2) The installation board of the control cabinet adopts a conductive metal plate to improve the grounding performance of the system.
Figure 5 Bakelite board for installing the baffle, grounded through a Thin and long wires cannot guarantee reliable connection
3) The casings of strong electric equipment such as filters, frequency converters, switching power supplies, and motor drivers are installed on a metal plate and are closely attached to
, as shown in Figure 4 shown.
4) At the entrance of each shielded cable into the control cabinet, the shielding layer must be grounded, and the grounding method of the shielding layer is shown in Figure 6 below.
Chart 6 The shielding metal layer is not grounded
Chart 7 How the cable shielding layer is grounded

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