The energy-saving effect of the frequency conversion device is very obvious. The variable-frequency speed-regulating motor is used in the high-power motor, and the entire generator set can save 30%. And after using the frequency conversion speed regulation, the soft start of the motor is realized, the motor works smoothly, the motor bearing wear is reduced, and the service life and maintenance period of the motor are prolonged. Therefore, the frequency conversion speed control technology has been widely used in petroleum, metallurgy, power generation, railway, mining and other industries.
1. Cable symmetry design
For 1.8/3KW and below variable frequency motor special cables, and symmetrical 3+1 core and 4-core cable can only be used for the input cable of the main power supply, but the symmetrical structure cable is used. Both the inverter and the inverter motor cable must adopt a symmetrical cable structure. The symmetrical cable structure has three cores and three +3 cores. The 3+3 core cable structure is the fourth core of the three large one small four core insulated cores ( The neutral core is decomposed into three insulated cores with smaller cross-sections, and the three big three small cores are symmetrically cabled. For the 6/10kV variable frequency motor special cable, the cable structure is different from the 6/10kV ordinary power cable. The ordinary power cable is to shield the three insulated cores with copper strips, and the special cables for variable frequency motors are shielded by copper wire and copper strips, and then packed into phase-separated jackets, then symmetrically cabled, and the symmetrical cable structure is due to the mutual Transmutability, better electromagnetic compatibility, play a certain role in suppressing electromagnetic interference, can cancel the odd frequency of high-order harmonics, improve the anti-interference of special cables for variable frequency motors, and reduce the whole system Electromagnetic radiation.
2. Design of shielding structure
The shielding of special cables for 1.8/3kV and below is generally used for general shielding. The special cable shielding for 6/10kv variable frequency motor is composed of split phase shielding and total shielding. The phase separation shielding can generally be shielded by copper tape or copper wire copper tape. The total shielding structure can be copper wire copper tape combined shielding, copper wire braiding shielding, copper tape shielding, copper wire braided copper tape shielding, etc., and the shielding layer section and the main wire core section are proportional. The shielded cable of this structure can resist electromagnetic induction, poor grounding and power line conduction interference, reduce inductance and prevent excessive induced electromotive force. The shielding layer not only acts to suppress the external emission of electromagnetic waves, but also serves as a channel for short-circuit current, and can play a protective role for the neutral core. 6/10kV variable frequency motor special cable, taking into account that the cable is often subjected to radial external force during use, adding galvanized steel strip pinning layer outside the cable shielding layer (adding a spacer between the shielding layer and the steel strip pinning layer) ). The steel strip is mainly used as the radial mechanical protective layer of the cable, and it also plays an additional general shielding function, especially the steel belt armor and the copper wire and copper belt shielding. It adopts two different shielding materials. The electromagnetic wave shielding plays a certain complementary role, and the shielding effect will be better.
3. Cable electrical performance design
The electrical performance of 1.8/3kV and below special frequency conversion motor cables is designed according to GB/Tl2706, 2002 standard. The 6/10kV inverter motor special cable meets the GBT/l2706.2002 standard and increases the electrical performance requirements of capacitors and inductors. According to the actual use of the special motor cable for variable frequency motor and with reference to GB/T12706.2002 and ABB Japan's technical conditions for the electric drive cable, the electrical performance parameters of the cable are determined.
4. The main manufacturing process of the cable
In the production process of special-purpose cables for inverter motors, the process of extruding the core of the insulated core and the process of cabling are the key processes of Zui.
The quality of the insulated core of the insulated core extrusion process will directly affect the electrical performance of the cable. In order to improve the quality of the cable, we choose high-performance insulation materials, such as 1.8/3kv inverter motor special cable, 10kV cross-linked insulation material, 6/10kv inverter motor special cable with 35kv cross-linked insulation material, conductor shielding, insulation shielding Imported materials are used for insulation materials. In the production process, we pay special attention to the purification of raw materials, shielding and insulation materials tightly packed, controlling the insulation eccentricity and the uniform outer diameter of the insulation, which can reduce the interface effect and improve the electrical performance of the cable.
The cable-forming process variable frequency cable requires structural symmetry. When the cable is cabled, 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, structural changes will occur, resulting in non-uniformity of capacitance and inductance, affecting the cable. Electrical performance.
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