A question about cables
Thread Content
I have a question about power cables that I’d like to ask everyone. Typical power cables are of the 3+1 type (three phases + neutral wire) or the 3+2 type (three phases + neutral wire + ground wire). Today I saw a cable designed specifically for variable-frequency motors, which is of the 3+3 type; it is represented in the picture as 3*120+3*25. I would like to ask how to make the connections? Does it not accept 3*25 and only accepts 120? Still in pairs of 120 and 25? Why is it designed this way? What are the advantages? I would appreciate your advice
For this type of cable designed specifically for 3+3 variable-frequency motors, the typical wiring method involves using three cables with a cross-sectional area of 120 square millimeters as the main power supply lines, to transmit three-phase power； The other 3 cables with a cross-sectional area of 25 square millimeters are used to transmit the ground wire, neutral wire, and control signals. The specific wiring method can be determined based on actual requirements and equipment specifications. If the equipment only requires a three-phase power supply, it is possible to use 3 cables with a cross-sectional area of 120 square millimeters, instead of 3 cables with a cross-sectional area of 25 square millimeters. If the device requires a ground wire, a neutral wire, and control signals, then these three 25 square millimeter cables need to be connected to the device along with the main power supply lines. The advantage of this design is that it allows power and control signals to be transmitted over a single cable, simplifying the wiring layout and reducing the number of cables as well as the space required. Furthermore, the use of cables of different specifications allows for meeting various current and power requirements, thereby enhancing the safety and reliability of electrical equipment. It should be noted that when making actual wiring connections, it is recommended to follow relevant electrical installation standards and the requirements of the equipment manufacturer, in order to ensure proper and reliable wiring and thus guarantee the proper operation of the equipment as well as personal safety. .
I guess this thin three-core cable is meant for the motor’s separate fan, with the equipment being grounded on-site
The motor’s separate fan is probably meant for cooling, right? But if it’s for cooling, the cables used should not be that thick; cooling fans usually have a power rating of a few hundred watts.
Yeah, true, I didn’t look closely: lol
This cable is of the 3p+3n series and is suitable for TN-C grounding systems； Or the 3p+3n/e series, suitable for TN-S grounding systems ； 3-core thick wire for connecting to the motor leads ； The thin three-core cable consists of the phase and neutral wires ； Baidu’s version, let’s learn that too!
The 3+3 core cable structure involves splitting the fourth core (the neutral core) among the four insulated core wires – three large cores and one small core – into three insulated cores with smaller cross-sections. These seven cores are then bundled in a symmetrical manner. For cables designed specifically for 6/10 kV variable-frequency motors, this cable structure differs from that of ordinary 6/10 kV power cables. Ordinary power cables have their three insulated cores shielded with copper tape before being bundled together, whereas cables for variable-frequency motors are first shielded with copper wires and tape, after which phase-specific protective sleeves are applied and the cores are bundled symmetrically. The symmetrical cable structure allows for greater interchangeability of the conductors, resulting in better electromagnetic compatibility; it helps to suppress electromagnetic interference by canceling out odd-frequency components, thereby enhancing the interference resistance of these cables and reducing electromagnetic radiation throughout the system.