The most important factor to consider when selecting the proper cable size is how well it can handle the needed current load in your installation setting without generating an excessive voltage drop from the supply voltage. Here are some of the conditions that will influence the eventual cable size you choose once you know the load that the cable will carry (Ampere). The considerations listed below may lead you to a different recommended conductor size. The key is that the minimum conductor size you choose must at the very least be the smallest cable size that can cover all the circumstances you've investigated. Following are some considerations you should look into before purchasing power cables:
1. Method of Installation: The first thing we look at is how and where the cable will be installed because how and where a cable is installed has a direct impact on whether it can be overloaded. In general, the more confined the cables are (e.g., in conduit versus open air), the larger the cable size is required to ensure that it can resist the current and allow proper heat dissipation.
2. Material of the Cable: The cable insulation material (the extruded layer that follows after the conductor) is critical for cable sizing because it directly impacts the maximum operating temperature of your cable. For your convenience, we've included common insulation materials such as PVC, XLPE, and EPR in the guide. PVC has a maximum working temperature in typical cable materials. Given the lower maximum working temperature of PVC, you might question why we would choose it over XLPE. This would be due to the material's other qualities that are more appropriate for your installation setting. PVC, for example, is far more flexible than XLPE and hence may be a better choice where the cable must bend in confined places.
Depending on the installation requirements, you can pick between single-core and multi-core cables, which will affect the cable's current carrying capability. A single core cable can disperse heat more effectively than a multi-core cable, resulting in a larger current carrying capability. However, you may still choose the multi-core cable because installing all the essential conductors at once may be easier.
3. Length of the Cable: To calculate Voltage Drop, which is the loss of electrical potential along your cable run, we need the length of your cable. The voltage drop of a cable run in Singapore must not exceed 4%, according to the SS638 (previously known as CP5) wiring regulations. The cable size and length of a cable line determine the voltage drop of a circuit. The greater the voltage loss, the smaller the cable size employed, or the longer the cable length required for your circuit. If the voltage drop of the circuit exceeds the specified 4%, you will need to upgrade your cable.
4. Temperature in the Environment: Our tables are based on a normal ambient temperature of 30 degrees Celsius in free air or a ground temperature of 15 degrees Celsius at a depth of 0.5 metres. Keep in mind that cable routing and ventilation have a direct impact on your ambient temperature, therefore, it's crucial to think about the installation condition throughout the length of the wire. If the temperature varies from the standard, a correction factor must be applied to the current load that your cable is supposed to carry. If your ambient temperature is higher than normal, you may need a larger cable to handle the required load.
5. Count of circuits: Our tables assume you're installing a single-phase or three-phase circuit. If you want to group circuits in your installation, you'll need to use a cable grouping correction factor to make sure you have the right cable size to avoid overheating problems. The greater the number of circuits you wish to group, the more difficult it will be to dissipate heat, thus you may need to increase the cable size appropriately.
We hope that this article has provided you with a general understanding of some of the major elements to consider when deciding on the minimum cable size to use. Cabcon India is a fantastic place to go if you're seeking industrial cables like binding wires, fibre cables, and other types of cables. Visit www.cabconindia.com for more information.
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