Motor wire eddy current problem

Ahah, regarding the eddy current issue for this sea user, it mainly depends on your cable model! Eddy current is defined as follows: when alternating current is passed through a coil with an iron core, alternating magnetic flux passes through the core, which in turn generates induced currents within the core. These currents form closed loops within the core, and their shape resembles vortices in water; hence they are called eddy currents. As for whether there are eddy currents inside your motor, it is mainly a issue related to motor manufacturing; generally, measures are taken to suppress them, so there’s no need to worry about it! For cables and junction boxes, the main issue is cable eddy currents. The eddy currents in cables arise mainly from three aspects of the cable structure: first, the copper shielding layer of three-core cables ； The second is the metal sheath layer of single-core cables ； Third is the cable armor layer. The original poster should check whether their cable falls into one of the three types mentioned above; if it doesn’t belong to any of these three categories, then there certainly won’t be any eddy currents!

The motor’s power inlet has a circular section that resembles a steel pipe, and single-core wires cannot be passed through such pipes (using a single-core wire in a steel pipe is equivalent to using an instrument transformer with one turn on both the primary and secondary sides, which generates eddy currents). If you divide the 4 wires into 2 pairs and pass one wire through each pair, it’s as if single-core wires are being used, which is theoretically not allowed. However, in practice, there might be some compensation effect when the two openings are close to each other, and since the length of the power inlet is short, the heat generation isn’t as significant as one would expect. If there is really no other option, the temperature rise can be measured experimentally; it is recommended to use a cable conversion box to switch to smaller cables or to use two smaller cables instead.

The cable is armored, with a 4*150 configuration; the motor is an explosion-proof three-phase asynchronous motor, featuring two power inlet ports, with two cables running through each port

Do eddy currents occur when the three live wires of the motor pass through one hole, while the ground wire passes through a separate hole?

Ahaha, hello there, sea friend! First of all, whether there are eddies or not, the wiring in your facility violates design specifications as well as the installation rules for explosion-proof electrical equipment; the motor wiring box simply cannot be made explosion-proof, which represents a serious safety hazard. You need to make corrections right away! Otherwise, why would you need explosion-proof motors on site? Since you have chosen explosion-proof motors and armored cables on-site, my suggestion is to use explosion-proof glands for the motor’s power inlet connections. There are two cable inlet ports for the motor; their purpose is to allow wiring when the motor cable is split into two strands, so that the wiring can be done through these two ports, rather than to divide a single cable into two parts for insertion into the wiring box

If the 3 live wires pass through one hole and the ground wire passes through another, no eddy currents will be generated. But as mentioned above, this approach is not allowed in explosion-proof areas. You can send me the outer diameter of the armored cable, the outer diameter after the armor is removed, and the thread size at the motor’s power inlet; I’ll check whether there are any suitable explosion-proof cable clamps or sealing fittings available. I’ve dealt with this issue of overly small gland sizes on imported motors on many occasions.