RE: Re: (ET) charging circuit

[Paul and Sue Abendroth <pabendro gemair com>]

At 07:06 AM 2/5/04 , Jeff wrote:

Does anyone have a link to a site the explains how this thing works? (in 
simple terms.)
I am at loss in understanding why the transformer will not work when the 
capacitor dies.

Thanks





Here is an excerpt from the following site

http://www.allaboutcircuits.com/vol_2/chpt_9/6.html



 "Ferroresonance" is a phenomenon associated with the behavior of iron 
cores while operating near a point of magnetic saturation (where the core 
is so strongly magnetized that further increases in winding current results 
in little or no increase in magnetic flux).

While being somewhat difficult to describe without going deep into 
electromagnetic theory, the ferroresonant transformer is a power 
transformer engineered to operate in a condition of persistent core 
saturation. That is, its iron core is "stuffed full" of magnetic lines of 
flux for a large portion of the AC cycle so that variations in supply 
voltage (primary winding current) have little effect on the core's magnetic 
flux density, which means the secondary winding outputs a nearly constant 
voltage despite significant variations in supply (primary winding) voltage. 
Normally, core saturation in a transformer results in distortion of the 
sinewave shape, and the ferroresonant transformer is no exception. To 
combat this side effect, ferroresonant transformers have an auxiliary 
secondary winding paralleled with one or more capacitors, forming a 
resonant circuit tuned to the power supply frequency. This "tank circuit" 
serves as a filter to reject harmonics created by the core saturation, and 
provides the added benefit of storing energy in the form of AC 
oscillations, which is available for sustaining output winding voltage for 
brief periods of input voltage loss (milliseconds' worth of time, but 
certainly better than nothing).
Unfortunately, these devices have equally noteworthy disadvantages: they 
waste a lot of energy (due to hysteresis losses in the saturated core), 
generating significant heat in the process, and are intolerant of frequency 
variations, which means they don't work very well when powered by small 
engine-driven generators having poor speed regulation. Voltages produced in 
the resonant winding/capacitor circuit tend to be very high, necessitating 
expensive capacitors and presenting the service technician with very 
dangerous working voltages.



Paul Abendroth        pabendroth dma org

"I think that wind is a species of air."
    Adelard of Bath, A.D. 1120