Hi Day
On (25 Dec 97) Day Brown wrote to Roy J. Tellason...
 RJ> Why would you assume that one of those would have hysteresis? 
 DB> *ANY* inductor would have hysteresis,
Gee I love an argument, especially after being whipped by others!@
Surely the only inductors that have hysteresis, are the iron based eg ferrite
ones.
An air- or non- ferric based inductor should be free of hysteresis.
Conventionally the hysteresis is expressed as an energy loss, the amount of
loss is illustrated by the area of the area entrapped by the B-H curve. 
hat's
the figure that lookes like a double "S" when plotted on linear graph paper.
The one "S" being different in shape from t'other.
which in this case, is of 
 DB> some considerable use.  The buildup of magnet flux in ferrite can 
 DB> not quite keep up with the steepness of a spike from a gate, or a 
 DB> spike on the input power line, and it is the *change* in that flux 
 DB> that induces current in the secondary- which is fed to a computer 
 DB> power supply. 
Technically, it is the *rate of change* rather than the *change* that
determines the induced current.
 DB> Looked at another way, if the input were an audio signal, we would 
 DB> notice a loss in fidelity, which in this case, we want.  I have a 
 DB> 10 amp autotransformer (10 lb?) which is of course, resonant to 60 
 DB> hertz.
Surely not RESONANT at 60Hz? Wouldn't that be inconvenient in a power
trannie??
 throw a spike at it, or a series along simulated inverter
 DB> sin wave output, and the spikes, which are the result of a 150KZ 
 DB> switcher, just get soopped up with all those soft iron leaves- as 
 DB> that much mass cannot change it's magnetic flux so easily. 
Warning- tho the iron leaves will sop up the magnetically coupled spikes,
there is a second route to worry about- the capacitance distributed along the
windings. For steep spikes and high frequency AC, this capacitance "conducts"
the spike really well. That's why transformers sometimes have an earthed
shield between primary and secondary windings- to suppress the spike or
"noise" so it doesn't travel via capacitance.
Cheers......ALEC
... Alzheimer's......... New Friends Every Day
--- PPoint 1.92
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