Inductive Kickback

[synchro1]

The battery's the source; The inductor the destination. Power moves away from the battery toward the inductor. The inductor stores the power from the battery in a magnetic field that expands Outward from the center of the inductor. When the current is interrupted, the magnetic field collapses Inward toward the center of the inductor and the inductor becomes the source. The flyback current then moves away from the inductor. Current moving away is in the opposite direction as current moving toward.

[AlienGrey]

Struth thats more confusing for my brain this time of night.

lets suppose we have a relay in the collector of an NPN transistor when we engage the relay
by turning the NPN trasistor on, energy will build up in a race to saturate the coil.

All is fine till we turn the device off thus disconnecting the supply we now have an inertia problem
where the electrons build up in the same direction, as far as i know if we have way to dissipate the energy
the voltage will reverse  and unless you have a protection diode between the + power rail and the transistors collector
(across the coil in the revers direction the fly back will destroy your transistor in its attempt to escape.

[synchro1]

@Aliengray,

This inductor discharge curve is the only thing you need to concern yourself with: Flyback takes the path of least resistance. The notion that there's some kind of inertia in the inductor is complete hogwash.

[synchro1]

The flyback is at a higher voltage potential then the source voltage; so if the resistance between the switch contacts is less then the resistance to ground, the flyback current will spark jump the gap to return to source across the open switch.

Everyone's seen the way current flows from higher to lower positive poles in our split positive tests. 

Igor's reed switch spinner 2 sends flyback power back to the positive pole of the source battery through his reverse biased LED:

https://www.youtube.com/watch?v=vWvI7T7h3tk

[sm0ky2]

@Aliengray,

The notion that there's some kind of inertia in the inductor is complete hogwash.

Maxwell says otherwise


The inertia is defined as:


9.10938356x(10^-31)Kg * 0.0002m/s * [6.25x(10^18)*# of coulombs]
and the vector is along the wire, in the direction of the current.
This is the state of motion that has to be overcome when you switch the current off