There are many machines in your plants. All the machines are using electricity as their energy source. Now this electric energy is carried by the cables and cable carries current.
Every conductor has some resistance and that resistance produces heat which are the energy losses. The heating losses are directly proportional to resistance of the cable and directly proportional to square of the current flowing through it. If there is mismatch in the current and resistance of the cable, the heating losses would increase and energy will be wasted. Moreover if there is mismatch in the current and the cable rating, there will less heat dissipation and the cable temperature would also increase which will in turn burn out the cable.
Now consider a cable whose rating is 20A max and it is actually carrying current of 15A through it. In this case, the heat generation will be little and the cable temperature would also be maintained. Now suppose if the machine connected to that cable starts drawing 30A current through that cable, then what would happen? The heat losses would be more and there will be less heat dissipation than heat generation. This will start increasing the temperature of cable and the cable may burn after some time.
So to save this extra heat generation in the cables, we must match the rating of the cable with the current flowing through it.
Good Luck !!
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