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Old 03-01-2009, 08:24 PM
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Aaron Aaron is offline
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not back emf

Originally Posted by darkwizard View Post
Flyback diode - Wikipedia, the free encyclopedia

Induction at the Opening of a Contact

According to Lenz's law, if the current through an inductance changes, this inductance induces a voltage so the current will go on flowing as long there is energy in the magnetic field. If the current can only flow through the air, the voltage is therefore so high that the air conducts. That is why in mechanically-switched circuits, the near-instantaneous dissipation which occurs without a flyback diode is often observed as an arc across the opening mechanical contacts. Energy is dissipated in this arc primarily as intense heat which causes undesireable premature erosion of the contacts. Some energy is also lost from the system as a whole and from the arc as a broad spectrum of electromagnetic radiation, in the form of radiowaves and light. These radiowaves can cause undesirable clicks and pops on nearby radio receivers.
Yes and none of that is what Back EMF is. AND Back EMF is always LOWER than what is applied. Lower, therefore, it is NOT the spike, which can be many times higher. Back EMF is also defined as being the opposing current DURING the application of power and NOT when disconnecting the power.
Aaron Murakami

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