why inductor is getting warm & burn in voltage regulator-lm2576
More details are needed but the inductor heats up due to two loss mechanisms:

1) Resistive losses.  Make sure you did not select an inductor with too low current rating.  I'd guess that this is the cause for the inductor to heat up.

2) Core losses.  An inductor is typically formed by a coil wound around a magnetic core.  As the current through the inductor looks like a triangle due to switching, the magnetic core flux fluctuates as well.  Since the magnetic material B-H curve is not perfect, some energy is lost each switching cycle.  The higher the switching frequency, the higher the loss.  Make sure your inductor can operate at the frequency of the LM-2576 regulator (52 kHz).

Mainly, make sure your inductor meets the rated current requirements.

From the LM-2576 datasheet, page 17:

An inductor should not be operated beyond its maximum rated current because it may saturate. When an inductor begins to saturate, the inductance decreases rapidly and the inductor begins to look mainly resistive (the DC resistance of the winding). This will cause the switch current to rise very rapidly. Different inductor types have different saturation characteristics, and this should be kept in mind when selecting an inductor. The inductor manufacturer's data sheets include current and energy limits to avoid inductor saturation.