Why current flows in nutral? As per theory there should be
no current in 3 ph explain.
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Answer Posted / ujjwal karki
1. As per the theory, No current should be flowing in the neutral. But this is theoretically possible when the load in each phase are perfectly balanced. As the switching patterns of each loads in 3 phases are not exactly the same, some amount of neutral current is likely to flow through the neutral.
2.Another likely cause as to why there is current flowing in the neutral is due to the effect of harmonics. Lets take an example of transformer. The Hysteresis loss in transformer causes a non-sinusoidal exciting current to flow which mainly comprises of third and fifth harmonics. Since the line-line third harmonic voltage is zero, these current can only flow through the neutral wire or around the mesh winding.(If these harmonic current donot get a path to flow, the flux in transformer is not sinusoidal and the output voltage is non sinusoidal as well!!). Hence, high current might be flowing in neutral and there is even the provision of doubling the size of neutral wire to prevent its overheating.
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