Problems with electrical control cables
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I have a question for everyone. The electrical transmitter sends motor operating signals and start/stop signals for the instruments. Can these two signals share the same cable? Thank you all.
It’s better to keep them separate; the start/stop signals can interfere with the operation signals!
For action 220, voltage level circuits should return to level 24; for different voltage levels, it is best not to use the same cable. In extreme cases, the interference voltage generated by action 220 activates all operating states directly.
Both the incoming and outgoing connections should be isolated by relays; it’s unlikely that 220V is applied directly.
I don’t understand: the status signal is a DI for the system, while the start/stop signal is a DO – so why is one wire used?
The DCS supplies power to the electrical DO contacts; where does the power for this circuit come from? If it comes from the electrical supply, it should be 220 volts ； If it comes from the instrument, then it should be 24. The voltage level of the circuit is determined by the power supply, not by the contacts. Circuits with different voltages should not share the same cable.
I’ve been looking up information these past few days; I’ll give the final answer now, and then we can close the replies to this post. Whether for cost reasons or not, the same cable cannot be used. The start/stop signals for the electrical cabinet carry a 220V voltage in the electrical circuit. The operating signal from the auxiliary contacts on the electrical contactor can be a dry contact. The two will cause interference, severely affecting the quality of the operational signals.
Dry contacts can also be used for the connection from the control cabinet to the electrical cabinet
Generally speaking, the start and stop signals for motors are separate; after starting, it’s not guaranteed that the motor will remain energized. Even if the instrument detects a loss of signal, this won’t affect the normal operation of the motor. Typically, a single set of signals is used to indicate the motor’s status. I hope my answer can be helpful to you.
Well, if I were the designer, I definitely wouldn’t design it in such a way as to create trouble for myself; no cost savings at all； If I were the owner, I would ask for a redesign ； If I were the supervisor, I would have the work redone ； If I were the construction contractor, it wouldn’t matter if I followed the drawings.