00000065.htm

LECTURE V,

SINGLE-ENERGY TRANSIENT OF IRONCLAD
CIRCUIT.

22. Usually in electric circuits, current, voltage*, the magnetic
field and the dielectric field are proportional to each other, and the
transient thus in a simple exponential, if resulting from one fonn of
stored energy, as discussed in the preceding lecturer. This, how-
ever, is no longer the cane if the magnetic field contains iron or
other magnetic materials, or if the dielectric? field reaches densities
beyond the dielectric strength of the carrier of the field, etc,; and
the proportionality between current or voltage and their respective
fields, the magnetic and the dielectric, thus cejises, or, an it may be
expressed, the inductance L in not constant, but varies with the
current, or the capacity is not constant, but varies with the voltage.

The most important cane in that of the ironclad magnetic* cir-
cuit, as it exists in one of the most important electrical apparatus!
the alternating-current transformer, if the iron magnetic circuit
contains an air gap of ^sufficient length, the magnetising force con-
sumed in the iron, below magnetic saturation, is small compared
with that consumed in the air gap, and the magnetic (lux, therefore,
is proportional to the current up to the values where magnetic
saturation begins. Below saturation values of current, the tran-
sient thus is the simple exponential discussed before.

If the magnetic circuit is closed entirely by iron, the magnetic
flux is not proportional to the current, and the inductance thus not
constant, but varies over the entire range of currents, following
the permeability curve of the iron, Furthermore¹!, the transient
due to a decrease of the stored magnetic energy differs in shape
and in value from that due to an increase of magnetic energy, since
the rising and decreasing magnetisation curves differ, as shown by
the hysteresis cycle.

Since no satisfactory mathematical expression has yet been
found for the cyclic curve of hysteresis, a mathematical calcula-
tion is not feasible, but the transient has to be calculated by an



	LECTURE V, SINGLE-ENERGY TRANSIENT OF IRONCLAD CIRCUIT. 22. Usually in electric circuits, current, voltage, the magnetic field and the dielectric field are proportional to each other, and the transient thus in a simple exponential, if resulting from one fonn of stored energy, as discussed in the preceding lecturer. This, how- ever, is no longer the cane if the magnetic field contains iron or other magnetic materials, or if the dielectric? field reaches densities beyond the dielectric strength of the carrier of the field, etc,; and the proportionality between current or voltage and their respective fields, the magnetic and the dielectric, thus cejises, or, an it may be expressed, the inductance L in not constant, but varies with the current, or the capacity is not constant, but varies with the voltage. The most important cane in that of the ironclad magnetic cir- cuit, as it exists in one of the most important electrical apparatus! the alternating-current transformer, if the iron magnetic circuit contains an air gap of ^sufficient length, the magnetising force con- sumed in the iron, below magnetic saturation, is small compared with that consumed in the air gap, and the magnetic (lux, therefore, is proportional to the current up to the values where magnetic saturation begins. Below saturation values of current, the tran- sient thus is the simple exponential discussed before. If the magnetic circuit is closed entirely by iron, the magnetic flux is not proportional to the current, and the inductance thus not constant, but varies over the entire range of currents, following the permeability curve of the iron, Furthermore¹!, the transient due to a decrease of the stored magnetic energy differs in shape and in value from that due to an increase of magnetic energy, since the rising and decreasing magnetisation curves differ, as shown by the hysteresis cycle. Since no satisfactory mathematical expression has yet been found for the cyclic curve of hysteresis, a mathematical calcula- tion is not feasible, but the transient has to be calculated by an 52