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.
For 1.8/3KW and below special-purpose wire and cable for variable-frequency motor, and symmetrical 3+1 and 4-core cables can only be used for the input cable of the main power supply, but it is better to use symmetrical structure cables. The symmetric cable structure is required for the inverter and the inverter motor cables. The symmetric cable structure has three cores and three cores and three cores. The core of the 3+3 core cable is the fourth core of the cores of the three major and minor cores ( The neutral core is decomposed into three insulated cores with smaller cross-sections, and the three large three-wire cores are symmetrically cabled. 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.
1.8/3kV and below frequency and special motor cables shielded general shield, 6/10kv special motor cable shield shield by the phase and total shield composition, phase shield can generally be used copper shield or copper wire combination shield . 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 of suppressing the electromagnetic wave from emitting to the outside, but also serves as a path of the short-circuit current, which can play a protective role of the neutral core.
For 6/10kV inverter motor special cable, the cable structure is different from 6/10kV ordinary power cable. Ordinary power cable uses three copper cores to shield the cable, and the special cable for frequency conversion motor is made of copper wire copper. After being shielded and jacketed with a phase-separated sheath, the symmetrical cable structure has better electromagnetic compatibility due to the interchangeability of the wires and plays a certain role in suppressing electromagnetic interference, and can cancel high-order harmonics. The odd frequency in the inverter improves the anti-interference of the cable for the inverter motor and reduces the electromagnetic radiation in the entire system.
6/10kV special-purpose cable for frequency conversion motor, taking into account that the cable is often subjected to radial external force during use, the galvanized steel tape armor layer is added outside the cable shielding layer (insulation sleeve is added 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 armored and copper wire and copper tape shielding adopt two different shielding materials. The electromagnetic shielding plays a complementary role and the shielding effect will be better.