Why does the coil of the contactor not be short-circuited after it is energized?

Yes, if you pull out the iron core and energize the air-core coil, the coil will heat up and burn out in a short time. If you pull the coil into a straight wire and energize it, the wire will burn out immediately! This proves that the current of the AC contactor coil originally installed on the iron core is very small. The principle is that when a straight wire is energized, an annular magnetic field will be formed around the wire. If the wire is wound into a coil, the annular magnetic field between adjacent coils will "unify" in the direction to form a strong cylindrical electromagnet, which will not only When nearby conductors are magnetically induced to generate mutual induction voltage, it will also cause self-induction voltage between the copper wires of the coil itself. Moreover, this self-induction voltage is in the opposite direction to the original applied voltage, so it will offset part of the original voltage and reduce the voltage. original current. Note that the magnetic ring of an energized straight wire will also produce a self-induction voltage. However, the annular magnetic field of a straight wire is very weak and the self-induction voltage is very small. The wires of the coil are close to each other, and the magnetic field of the adjacent coil is strengthened to make the turns The magnetic field will be felt stronger, the self-inductance voltage will be larger, and the resistance will be smaller than that of a single straight wire (its iron core can better gather the magnetic field).

(The DC relay coil will not burn if it is opened into a straight wire. This is the function of the copper wire resistance of the coil)