1. Insulation of the electrical breakdown of the inv […]
1. Insulation of the electrical breakdown of the inverter after a large number of applications
Most of the general selection of general power cables, such as PVC insulated, jacketed cable or XLPE insulated PVC sheathed cable, the cable itself, the level of pressure Higher, very little cable breakdown of the cable. This is obviously different from the above-mentioned deep well pump cable breakdown, deep well pump cable with polyimide / polyfluoroethylene propylene composite film wrapped around the package and ethylene-propylene rubber double insulation, from the thickness and insulation is not ideal, Oil pump cable length of more than 3 km, the working environment of the oil wells harsh, the cable in the high temperature, high pressure, oil and water conditions in the work, the insulation performance is more fragile, when the operation process by a variety of bad factors after the erosion of electricity, Thermal factor staggered lead to insulation breakdown. Why the cable in the frequency can be long-term operation and frequency breakdown within a few hours? This is by no means aging, basically due to the impact of high frequency pulse voltage. General use of the case, the use of PVC insulation is not ideal, because of its dielectric loss is too large. XLPE insulation is more satisfactory, it is organic, electrical, heat and other excellent performance. Cable insulation thickness can be used 1kV voltage level of the provisions, if appropriate thickening, of course, more reliable, which is more favorable for variable frequency cable.
2. High-frequency electromagnetic waves on the issue of environmental pollution
Although there is no national norms of cable emissions of electromagnetic waves caused by environmental pollution assessment indicators, but the suppression of external high-frequency interference is necessary to do. For the four-core low-voltage cable, the first is to improve the arrangement of insulated wire core, if the cable four core directly into the cable, is asymmetric structure, if the fourth core is divided into three smaller cross-section insulation core, the three three Small core symmetrical cable, two cases compared to symmetrical type more favorable. The second should be considered more important is to strengthen the total shielding structure. Manufacturers are accustomed to using copper wire braid shielding, in fact this is not a good way, material consumption, processing speed is slow, shielding effect is not the best. The use of copper belt cover and embossed is a more advanced structure and technology, forming a fully enclosed metal layer, as long as the thickness of appropriate, can achieve effective shielding function. And this process and its use of materials in the field of fiber optic cable has been very common, copper strip thickness can not be too thin, to ensure that the suppression of electromagnetic waves external launch.
3. Shield Grounding Measures
Shield Grounding is a necessary condition to suppress the external launch of electromagnetic waves. The grounding method of copper braid shield is easier to be solved, and the vertical copper tape embossing is required to use special fixture grounding, fixture and embossed brass Of the contact surface should be anastomosis, the ground wire leads from the end of the fixture.
4. Additional test of cable
The general low voltage cable does not need to carry out pulse voltage test, such as IEC 60502 standard only 3.6 / 6 kV and above the cable is required for pulse voltage test. The connection cable of the variable frequency motor is slightly different and needs to withstand the high frequency pulse voltage. High frequency wave amplitude of up to 1200 ~ 1900 V, ringing frequency of about 100 ~ 2000 kHz, the pulse voltage test on the cable (type test) is to reflect the cable insulation level. Test can refer to the IEC 60502 standard, that is, the application of plus or minus ten pulse voltage test, the test voltage can be considered 40 kV, but need further verification, it is necessary to determine the factory.