Cable selection for 250KW variable-frequency screw air compressors
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This post was last edited by ynjh on 2017-7-4 at 18:34. The company has recently purchased a 250KW variable-frequency screw air compressor. When asking the manufacturer’s technical staff about the specifications of the compressor cables, it was clarified that our role is to supply power to the inverter, as their inverter and compressor are integrated together. The voltage is 380V. The manufacturer’s response is as follows: For the power cable, a single 185-square-millimeter wire is used; two such wires are combined to connect to the main power supply. For each air compressor, six 185-square-millimeter wires are used, with two of them combined to connect to the R, S, and T terminals. As for the ground wire, a single 185-square-millimeter wire is used as well. Could experts help calculate whether using 185-square-millimeter wires is an excessive choice? Also, why 6 wires? Is 185 a too large size for the ground wire? I’m not an electrical engineer, so I hope experts can help answer this. Thank you very much; I’m in a hurry!
It should be a YJV22 cable (copper core) with a cross-section of 3*185+1*95. The rated current for a 250kW motor is 360A, and the current-carrying capacity of the YJV22 cable with 3*185+1*95 configuration is 420A (when the copper core is buried). So it’s fine to use double-pair cables
This post was last edited by Electric Apprentice on 2017-7-5 09:31. You’re wrong; according to what the original poster said, the cable chosen by the manufacturer should be a single-core 185 gauge cable, not a 3*185+1*95 cable. Moreover, based on the latest specifications, the current-carrying capacity of a directly buried 3-core 185 gauge cable is not 420, but rather 280. The current-carrying capacity of a single-core 185 gauge cable is 301. Since the rated current for a 250kW air compressor is 360A, it’s necessary to use two cables together. There are two advantages to using two cables: first, the overall current-carrying capacity increases; second, it makes wiring easier. So, the incoming wires are 6 strands of 185 square millimeters each, with two strands combined together to be connected to the power terminals R, S, and T
There are too many issues with Version 4; better wait for the revised version. But as you said, it should be a single-core 185 cable.
There is no problem with this. I would also choose two 185 cables to use in parallel. The manufacturer recommends using single-core cables, with two of them used together as one cable; thus, there are 6 cables in total for the three phases. The ground wire also **has specified requirements; it must not be less than half of the length of the phase wire.
There is no problem with this. I would also choose two 185 cables to use in parallel.
The current-carrying capacity of the cable paired with it, as you can see, is for high voltage of 6–35 KV, right?
Everyone, for a motor with 250KW capacity and 380V voltage, how is the calculation done? The current is only 260A, right? ? Is it my question that’s wrong? ? Or did everyone make a calculation mistake? ? ?
I misread it; the current-carrying capacity for 0.6/1 KV is even lower
How did you calculate that it’s only 260A? ? ?
A motor with a power of 250KW and a voltage of 380V can have a current of up to 475A. With two 185 cables, the current can be around 740A (2x370A); this is feasible. However, using 185 cables is not economical