Flyback peak

[1843]

Hi all,
How it is possible that one PI detector sends several hundred volts into the coil with only a 12v battery?
Explane for me, please.

Regards

[PhilippeM]

SOLUTION

You can find all information here: http://www.ee.surrey.ac.uk/Workshop/...s/faraday.html

That depend from the LENZ law: it's a electromagnetic law.
Bests regards
PhilippeM

[Carl-NC]

The relationship between the voltage and current for an inductor is:

v(t) = L * di(t)/dt

Plus an initial condition that we'll ignore. So for a sinusoidal current, the voltage is just a phase-shifted sinusoid. For a DC current, the voltage is zero. But if that DC current is suddenly turned off, then the di/dt can get very large, resulting in a voltage that can exceed the power supply.

Ferinstance, say a 1mH inductor has 1 amp of current (easy to do). We open a switch and the current drops to zero in 1us (easy to do). The peak voltage will be:

v(t) = 1mH * 1A/1us = 1000 V

- Carl