Wiring advice | Connections and routing
Wiring industrial control panels is a complex process that requires a number of carefully planned and completed details.
Connections and routing tips for industrial control panel wiring (photo credit: powerindustrialcontrols.com)
However, there are a dozen tips and tricks on how to do this and that, but this tech article will be limited to wired connections and routing inside control panels.
Now let's discuss the tips to consider when wiring the control panel:
- General advice
- Conduit and cable
- Conductors of different circuits
1. General advice
Here are some general points to consider when wiring the control panel.
1. The connections should be secure against accidental loosening. Tighten the terminal screws properly and, when a connecting plug is installed, use the clamps or screws provided to secure it to the corresponding socket.
2. Particular attention in this regard should be taken with the protection circuit, for example using star washers and a nut if necessary.
3. Two or more conductors can only be connected to a terminal designed for this purpose. Most terminal blocks only take one or two conductors. Do not force anymore.
4. Add an additional terminal and connect it to the other by a link inserted in the trucking to gain an additional connection point.
5. Solder connections should only be made to terminals suitable for this purpose. Transformers can be fitted with appropriate turret labels for soldering, and printed circuit board assemblies can have solder pins.
6. Terminals and terminal blocks must be clearly identified and identified corresponding to the markings on the drawings. Make sure that the identification labels and cable markers are legible, marked with permanent ink, and suitable for the environment where the panel is to be used. They should also match those shown in the machine drawings and maintenance instructions or documentation.
7. A means of retaining the conductive strands must be provided when the terminals are not equipped with this installation, for example by crimping on starting tips. Do not use solder.
8. The terminations of shielded or shielded conductors should be terminated so that the screen cannot fray. If the display needs to be connected, turn it off in the same way as for the coaxial cable with a welded pigtail and sleeve. If not, cut it as much as possible and cover it with a sleeve. The terminations of screened or screened conductors must be terminated so that the screen cannot fray
9. Terminal blocks must be mounted and wired so that internal and external wiring does not cross the terminals. The terminal blocks must be mounted and wired so that the internal and external cables do not cross between the terminals.
10. Flexible conduits and cables should be installed so that liquids can drain from fittings and terminations.
2. The conductor and the cable
1. Conductors and cables must go from terminal to terminal without intervening joints. It is about making a joint in the middle of a wire or a cable. If necessary for any reason, use an appropriate connector or terminal block. Do not use a twisted and welded joint. The extra length must remain at the connectors where the cable or cable assembly is to be disconnected during maintenance or service. Conductors and cables must pass from one terminal to another without any junction.
2. Multicore cable terminations must be properly supported to avoid undue stress on the conductor terminations.
3. As much as possible, the protective conductor should be routed close to the associated live conductors to avoid excessive loop resistance.
4. Conductors of different circuits This refers to wires and cables that are in the same enclosure but are connected to different parts of the system, for example, electrical wiring that can withstand high currents at 415 volts.
Signal wires that can be connected to the sensors and input terminals of a PLC, therefore, carry only low currents of 5 to 24 volts.
When a conductor carries current, an electromagnetic field is produced. This is more pronounced when the horsepower is high as can be the case with a powerful ac motor. This field can generate a voltage in other conductors nearby. It is possible that this so-called interference voltage will cause another circuit to react, causing it to malfunction.
When the current is turned on or off, the electromagnetic field increases and decreases, in effect rapidly causing a radio signal. The effect is similar to the crackle you can sometimes hear on the radio or television when something like a refrigerator turns on and off. This radiated signal can be picked up by other wires in the system and cause interference with the normal system operating voltages. This is known as Electromagnetic Interference or EMI. The Electromagnetic Compatibility (EMC) Regulations require that these effects be minimized.
In many cases, it is the layout of the wiring that is essential to avoid interference and the designer will have been aware of this. This aspect of wiring relates to EMC regulations. The layout of this wiring must be specified by the designer and must be observed. When circuits operate at different voltages, the conductors should be separated by appropriate barriers or all wires insulated for the highest voltage to which any conductor can be subjected. Circuits that are NOT turned off by the power disconnect device must be physically separated from other cables and/or distinguished by their color. so that they can be easily identified as being live when the disconnect device is in the off or open position.
An example of such a circuit is a lamp inside an enclosure intended for use in maintenance. The control panel can be isolated, but the lamp requires power for the engineer to see while working on it.