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1. Cable symmetry design
For 1.8/3KW and below special-purpose inverter motor cables, and symmetrical 3+1 and 4-core cables can only be used for main power input cables, but it is better to use symmetrical structure cables. Inverter and inverter motor cables must use symmetrical cable structure. The symmetrical cable structure has three cores and three cores and three cores. The core of 3+3 cores is the fourth core of the cores of the three major and minor cores (the neutral core). ) Decomposed into three insulated wires with small cross-sections. The three large three-wire cores are symmetrically cabled. For a 6/10kV special-purpose cable for frequency-converter motor, the cable structure is different from that of a 6/10kV ordinary power cable. Ordinary power cable The three insulated cores are shielded with copper tape, and the special-purpose inverter motor cable is shielded by copper wire and copper tape to encapsulate the phase-separated sheath and then symmetrically cabled. The symmetrical cable structure is due to the interchangeability of the wires. Better electromagnetic compatibility plays a role in suppressing electromagnetic interference. It can cancel the odd-order frequency in high-order harmonics, improve the anti-interference of special-purpose cables for frequency conversion motors, and reduce the electromagnetic radiation in the entire system.
2. Shield design
1.8/3kV and below special frequency motor shielded cable generally use the total shield, 6/10kv special motor cable shield shield by the phase shield and the total composition of the shield, split shield can generally be copper shield or copper wire and copper strip combination shield. The total shielding structure can be copper wire copper belt combination shield, copper wire braided shield, copper tape shield, copper wire braided copper tape shield, etc. The cross-section of the shield layer and the main core cross-section are in certain proportion. The shielded cable of this structure can resist electromagnetic induction, poor grounding, and conduction interference of the power line, reducing inductance and preventing excessive induced electromotive force. The shield layer not only plays a role in suppressing the electromagnetic wave from being emitted to the outside, but also serves as a path of the short-circuit current, which can play a role in protecting the neutral core. 6/10kV special-purpose cable for frequency conversion motor, taking into account that the cable is often subjected to radial external force during use, increase the galvanized steel tape armor layer outside the cable shielding layer (insulation cover between the shielding layer and the steel tape armor layer ). Steel tape armor is mainly used as a radial mechanical protective layer of the cable. At the same time, it also serves as an additional total shielding function. In particular, steel tape armor and copper wire and copper tape shielding are used in two different shielding materials. The electromagnetic shielding plays a complementary role and the shielding effect will be better.
3. Cable electrical performance design
1.8/3kV and below special electrical cables for frequency conversion motor are designed according to GB/Tl2706, 2002 standards. The 6/10kV special-purpose inverter motor cable meets the requirements of the GBT/l2706.2002 standard, and increases the electrical and capacitive properties such as capacitance and inductance. According to the actual use of the special cable for variable frequency motor and reference GB/T12706.2002 and ABB Company's technical conditions for the electric drive cable, determine the electrical performance parameters of the cable.
4. The main manufacturing technology of the cable
In the production process of inverter-dedicated cables, the insulated wire core extrusion process and cabling process are the most critical processes.
Insulated core extrusion process The quality of the insulated core directly affects the electrical performance of the cable. In order to improve the quality of cables, we choose high-performance insulating material production, such as 1.8/3kv special-purpose cables for frequency conversion motor, 10kV cross-linked insulating material, 6kVv inverter-dedicated cable, 35kv cross-linked insulating material, conductor shielding, and insulation shielding Both insulating materials and imported materials are used.
The energy-saving effect of the frequency conversion device is very obvious. In the high-power motor, the frequency conversion motor is used, and the entire generator set can save 30% power. And after the use of variable frequency speed regulation, the soft start of the motor is realized, the motor is operated stably, the wear of the motor bearing is reduced, and the service life and the maintenance period of the motor are prolonged. Therefore, frequency conversion speed regulation technology has been widely used in petroleum, metallurgy, power generation, railway, mining and other industries.