Design of shielding structure
The shields of special cables for variable frequency motors of 1.8 / 3kV and below generally use general shielding, and the special cable shields for 6 / 10kv variable frequency motors are composed of split-phase shields and general shields. Generally, split-phase shields can be shielded with copper tape or copper wire copper tape. The overall shielding structure can be combined with copper wire and copper tape shield, copper wire braided shield, copper tape shield, copper wire braided copper tape shield, etc. The cross section of the shield layer and the cross section of the main wire core are in a certain proportion. The shielded cable of this structure can resist electromagnetic induction, poor grounding and conducted interference of power lines, reduce inductance, and prevent the induced electromotive force from being too large. The shielding layer not only plays a role in suppressing the external emission of electromagnetic waves, but also serves as a channel for short-circuit current and can protect the neutral core. Special cable for 6 / 10kV variable frequency motor. Considering that the cable is often subjected to radial external forces during use, add a galvanized steel tape pinned layer outside the cable shielding layer (add an insulation sleeve between the shield layer and the steel pin pinned layer) ). The steel strip pin is mainly used as the radial mechanical protection layer of the cable, and also plays an additional overall shielding role, especially the steel strip armor and copper wire, copper strip shielding, which uses two different shielding materials. The shielding plays a complementary role, and the shielding effect will be better.
Cable electrical performance design
The electrical performance of special cables for variable frequency motors of 1.8 / 3kV and below are designed according to GB / Tl2706, 2008. The 6 / 10kV frequency conversion motor special cable meets the GBT / l2706.2008 standard and adds electrical performance requirements such as capacitance and inductance.
Technical requirements for the main manufacturing processes of cables
In the production process of special-purpose cables for variable frequency motors, the process of extruding the insulated cores and forming the cables is the most critical process. Insulation core extrusion process The quality of the insulation core will directly affect the electrical performance of the cable. In order to improve the quality of the cable, we choose high-performance insulation materials for production, such as special cables for 1.8 / 3kv inverter motors, using 10kV cross-linked insulation materials, special cables for 6 / 10kv inverter motors use 35kv cross-linked insulation materials, conductor shielding, insulation shielding And insulation materials are imported materials. In the production process, we pay special attention to the purification of raw materials, tight shielding and insulation materials, control the insulation eccentricity and the uniformity of the outer diameter of the insulation, which can reduce the interface effect and improve the electrical performance of the cable. In the cable forming process, the frequency conversion cable requires symmetrical structure. During the cable forming, the tension of the insulated core must be uniform, so that the length of the core after the cable is kept as consistent as possible, otherwise it will cause structural changes, cause unevenness of capacitance and inductance, and affect the cable. Electrical performance.