The relationship between the physical and electrical properties of a conductor are very important in evaluating the current transmitted in the conductor. The ampacity is relating of the conductor size and the amount of current it transmits. This technique is used to limit the amount of current to be carried in a conductor. When a conductor is small it exhibits high resistance to the current flowing through it. With high resistance, there is high heat energy dissipation and an excessive heat can damage the conductor, the insulation system and even the appliances on the line. If the insulation is a plastic which is highly inflammable then a great flame may be caused.
The study of conductor ampacity is therefore very crucial because it exposes you to the knowledge of how to ensure you don’t transmit current with cables of wrong sizes. Certain codes and standards for wiring are enshrined in the NEC codes, in USA, may guide you. These code stipulate the maximum allowable currents for every category of cable sizes and their applications.
These are factors that will guide you when choosing the appropriate ampacity for your cables:
a) Voltage drop
Calculating the voltage drop across the conductor helps to approximate the correct ampacity. It helps you determine whether the size of conductor used is appropriate. A small voltage drop leads to an efficiently working system.
b) Conductor Length
When you want to transmit or distribute current over a long distance then you ought to consider the size of the conductor. Remember the greater the length of a conductor the high the resistance and the higher the voltage drop. When the conductor system has to cover a longer distance then consider increasing the size of the conductor so that you compensate for current lost due to resistance.
c) Conductor melting point
There are conductors whose melting points are very low. They can easily burn when they are heated with even a slight increase in temperature. What causes heating in the conductors is high resistance. Therefore for conductors with low melting point, their sizes should be increased so that resistance is decrease and chances of heating lowered. Conductors like copper whose melting point is high can be used in small sizes without major problems.
d) The quality of the Insulation
A good insulator is that one which cannot easily melt. When you know your insulator is prone to melting, it guides you on appropriate sizing of the conductor so that you don’t destroy the insulation.
e) Load size
The size of load to be driven by power also determines the size of cables you will use. You cannot drive industrial locomotives and opt for small sized cables. Bigger machines draw high voltage and that implies that the cables used must be able to transmit such high voltages.
The study of conductor ampacity is very vital when you want to work with electric wiring. With the help of NEC codes you can get the right cable size for your system. This boost the safety of your installation. I hope you found this insightful. For more information on conductor ampacity please get in touch with us at Nassau Electrical today.