Selection of motor control signal cables
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This post was last edited by The project’s progress on 2024-8-16 07:45. We have a project, and due to schedule constraints, the general contractor asked the electrical control manufacturer to prepare a list of cables to be purchased in advance. The motor control cables are to use RVV type. The specifications require that cables connected to the computer control system be shielded. The electrical control manufacturer said they have always used this approach, and there have been no problems. I would like to ask if anyone has used this method before – have there been any issues? I’m currently laying the cable trays separately, but they still need to be combined in the control room
If it’s not a 0-10 signal, there are basically no problems
The control of the motor involves controlling its start and stop, as well as providing feedback. The signals for starting and stopping the motor are in the form of alternating current; these signals are connected to the DCS’s DO output relays by wiring the motor’s contactor control circuit in parallel or in series. When starting the motor, the circuit is connected in parallel with the contactor coil, while when stopping it, it is connected in series with the control circuit. Of course, logically, the AC circuits that enter the control room should be shielded, so as to reduce the impact of alternating current on the control system. But the impact is minimal. The best approach is to place the DO relay amplification board in the power distribution room; the signals generated by the DO cards are connected to that room via multi-core wires. These wires do not need to be shielded, as they carry DC current signals in the range of 10–30 MA, which are used to drive the relay coils. Such signals have strong resistance to interference, and since they are DC, they will not cause any interference with the control system. Then, the relay amplification board in the power distribution room uses cables to connect to the control circuit of the contactor. In this case, the wire is short and no shielding is needed, as it is an AC signal of about 50 mA with strong resistance to interference.