(1) Ensure that any machine equipment grounding device in the motor control cabinet is excellent, and use short and thick grounding connections to the public address or grounding device copper bar. All control systems (such as a plc) connected to the variable frequency governor need to apply short and thick transmission line grounding devices rather than common ground. Flat electrical conductors (such as wire mesh) are generally selected because of their low characteristic impedance at high frequencies.
(2) The low voltage module of the motor control cabinet, the solenoid valve, and the AC contactor should be maintained by circuit breakers; When the connection between the frequency converter and the motor exceeds 100m, when the switching power supply volume of the frequency converter exceeds 600kw/a or the switching power supply volume of the power supply system exceeds 10 times the volume of the frequency converter, it is proposed to increase the input output reactor.
(3) Ensure that the AC contactor in the motor control cabinet has a magnetic blowing effect, the DC contactor uses r-c suppressor, and the DC contactor uses a "gear" diode and is installed in the winding. The choice of zinc oxide varistor suppressor is also very reasonable.
(4) If the machine equipment operates in a condition that is more sensitive to noise, filters can be used to reduce the impact of radiation sources. At the same time, in order to better achieve the actual effect, ensure that the filter and the assembly plate should have a good touch.
(5) The motor cable should be separated from other frequency conversion cables, and its smaller spacing is 500mm. At the same time, the parallel wiring of the motor cable and the frequency conversion cable should be prevented at a distance. If the frequency conversion cable and the host power cable are crossed, they should be crossed at a 90° Angle as far as possible. At the same time, the screen layer of the motor cable and frequency conversion cable must be fixed to the assembly board with a suitable clip.
(6) In order to better and reasonably suppress the coverage and transmission of radio waves, the motor cable of the frequency conversion governor must be shielded twisted pair, and the conductivity of the shielded layer must be at least 1/10 of the conductivity of each phase of the transmission wire core.
(7) The motor control cabinet shall be provided with a neutral line group and a protected line group (pe). The grounding device bank and pe conductivity bar must be connected to the bearing beam (copper to copper bar connection). They need to be around the place where the cable cap is directly opposite. The grounding device bank addition also needs to be connected to the maintenance power circuit (grounding device electrical bar) according to another cable. The shielded system bus is used to ensure that the shielded connection of each cable is reliable, and it completes the large-scale metal-to-metal connection according to a load-bearing beam.
(8) It is not possible to install the actual operating panel with a display screen near the cable line and the edge of the machine equipment containing inductors, such as switching power cable, AC contactor, solenoid valve, magnetic induction line valve, transformer, because they can form a strong electromagnetic field, endangering the measurement accuracy of the instrument equipment.
(9) The output power component (transformer, driving component, load output power switching power supply, etc.) and the control system (solenoid valve operation part, program controller) must be assembled separately. However, it is not suitable for output power components and control system design as one of the goods, frequency conversion governor and filter plastic housing should be connected with low resistors and electric control cabinets to reduce the impact of high frequency instantaneous current flow. The ideal scenario is to assemble the control module onto a good conductive, gray-black metal sheet and assemble the metal onto a large metal table surface.
(10) When designing the motor control cabinet, pay attention to the regional standards of emc, and plan different machines and equipment in different areas as a whole. Each region has different regulations on the transmission and anti-interference degree of environmental noise. It is more practical to isolate the area with a metal shell or a grounding device protection plate in the cabinet body. Moreover, taking into account the caloric value, the air duct of the motor control cabinet should be developed effectively, the exhaust system should be smooth, and the vortex in the cabinet should be prevented from producing dust deposits at certain places. The fan is generally installed near the air vent, the supply fan is installed at the lower end, and the air intake fan is installed at the upper end of the container.
(11) According to the waterproof level of the control box facilities, it is necessary to take into account the anti-fouling and waterproof effect of the control box, and the general application facilities are mainly: central air conditioning, fans, heat exchangers, and anti-cold electric heaters. At the same time, according to the number of boxes, the appropriate selection of different efficiency of the machine equipment. Regarding the selection of fans, the key is to consider the normal operating temperature in the cabinet, the higher operating temperature outside the cabinet, to find a temperature difference, the ventilation speed of the fan, and to estimate the volume of gas in the cabinet. Three data information have been known: temperature difference, ventilation speed, and gas volume, and then the duration of removing the gas in the cabinet is calculated, and the specific ventilation speed is calculated according to the temperature difference. Then select the specific fan. Since the ambient temperature is generally reduced at night, it will cause condensate to attach to the circuit board in the cabinet, so the corresponding anti-cold electric heater should be selected to ensure the ambient temperature in the cabinet.
(12) The main provisions of the frequency conversion governor connection the frequency conversion governor is well assembled in the middle of the control box, the frequency conversion governor should be vertically assembled, and the above and below should prevent the large components that are likely to block the exhaust system and supply air; The spacing between the upper and lower edges of the frequency conversion governor, the spacing between the top and bottom of the motor control cabinet, or the smaller spacing between the baffle and the large components that must be installed and used, should exceed 150mm; If the unique customer must remove the computer keyboard in use, the computer keyboard hole of the frequency conversion governor control panel must be strictly sealed with tape or replaced with a fake control panel to avoid a large amount of smoke into the internal structure of the frequency conversion governor.