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Originally Posted by lighty
I think the main problem is the lack of proper terminology practice. I use the term to label the induced EMF of the higher value and reverse polarity than the voltage of the source inducing the original current flow (and thus magnetic field) that manifests itself when the conductance of the coil circuit goes suddenly to zero and the magnetic field collapses very fast. Now look at this very vague definition that is somewhat contradictory in itself Counter-electromotive force - Wikipedia, the free encyclopedia
When I think of it I cannot remember a proper term used in electronics. The phenomena is mostly labeled as detrimental as it might burn out the semiconductor devices (and thus all the protective snubber circuitry usually engineered in the circuitry) and simply calls it "transient phenomena". While that term is appropriate because it is transient phenomena it's at the same time very vague so no luck there. Just look at here Snubber - Wikipedia, the free encyclopedia In relation to the transil diodes it's only mentioned that they protect circuit from the "voltage spikes". Transient voltage suppression diode - Wikipedia, the free encyclopedia
So what would be the proper terminology for that fast transient phenomena?  |
Lighty, Aaron, and anybody else who cares,
OK folks, here is the real answer. The Wikipedia definition for Counter Electromotive Force (CEMF) actually covers the territory pretty well. It is just a little short on detail. Technically, BACK EMF is the reverse voltage generated in an electric motor that is responsible for holding back the current when the motor speeds up. My DVD
Electric Motor Secrets shows exactly what the BACK EMF is and how it works.
CEMF is any other reverse induction in an inductor that slows down the increase or decrease in the applied current. This process is described by Lenz Law, where ANY induced current opposes the movement of the magnetic field that induced it. So, when a DC square-wave pulse is applied to a coil of wire, the voltage reaches its maximum value nearly instantaneously, whereas the current rises to its maximum value on a ramp-wave with a specific time constant. The current cannot rise instantaneously, like the voltage, because the current in one turn of the coil is causing CEMF inductions in other turns of the coil nearby. So the current fights itself to reach its maximum value. These processes only happen when the current is CHANGING, either rising or dropping in value.
In the older books, the distinction between these two processes, or the names used to describe them was not made. Many names for electrical processes changed in the 1950's and 1960's. Cycles-per-second became Hertz, CEMF became Back EMF and lots of other things. It is no wonder that there is confusion about these things.
The most important thing to understand in all of this is that all of these phenomena follow ELECTROMAGNETIC INDUCTION LAWS. Currents are induced in relationship to the strength of the magnetic field and voltages are induced based on the rate-of-change of that flux. In standard transformer operations, voltages in the output winding (secondary) cannot exceed the voltage in the input winding (primary) times the turns ratio between the primary and the secondary.
The appearance of the very short duration, very high voltage transient, when the current powering an inductor on DC is shut OFF, does not follow these Laws, especially on CLOSE OBSERVATION. John Bedini has spent 30 years studying this situation and has articulated most accurately the conditions to maximize the production of this voltage spike. I refer to this situation as the energy of "the inductive collapse", since that distinguishes it from other varieties of CEMFs. The voltage producing phenomena produces a different QUALITY of electricity, according to the "Method of Conversion" described by Tesla. In fact, charging and discharging an inductor is the FIRST STEP in Tesla's "Method of Conversion" and the first step in the process of producing PURE Radiant Energy.
According to Tesla, the "fast transient phenomena" is a Longitudinal Wave, a time compressed zone of electrostatic charge or pure voltage, traveling ahead of the electron current. It appears BEFORE the current starts moving and is separate and distinct from it.
I hope this helps.
Peter