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Патент USA US2134539

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Oct. 25, 1938. "
2,134,539
W. THAL
ALTERNATING CURRENT APPARATUS FOR TESTING MAGNETIZABLE MATERIALS
Filed April 4, 1955
IVVE
‘14/11. l-(EL
ATTOR/VE K5, ‘
Patented ‘Oct. 25,‘ 1938
" UNITED STATESIPATENT OFFICE
ALTERNATING CURRENT APPARATUS FOR
TESTING MAGNETIZABLE MATERIALS
Wilhelm Thal, Berlin- Siemensstadt, Germany, as
signor to Siemens & Halske, Aktiengesellsclhaft,
Siemensstadt, near-Berlin, Germany, a corpo
ration of Germany
'
Application April‘ 4, 1935, ‘Serial No. 14,633
Germany April "I, 1934
-
va Claims. (01. 175-183)’
Mvinvention relates to alternating current apparatus for testing magnetizable materials.
of iron test, that is to say the current-Voltage
measurement. An alternating-current source
The majority of methods for testing iron are (not shown) is connected to the terminals K1
based on a direct-current measurement. Since, and K2, the test piece P being energized by the
5 however, ‘such a measurement does not take into source through the Winding Wl- The measuring
5
consideration the eddy current losses extremely instrument (ammeter) J is inserted in the cir
important for all alternating-current instruments with The Secondary Winding W2 is connected
and since, furthermore, the results obtained by to the voltmeter E- Recti?ers R and R’ are in
the direct-current ‘measurement do not hold good dicated in series with the ammeter J and the volt
for the alternating-current magnetization the meter E respectively- A condenser C is con
Epstein apparatus has been contrived which nected across the connections K1 and K2 of the
permits of measuring, ‘in the case of altemsh, primary windings and in parallel withthe alter
ing-current, the losses and the alternating-cur-
nating current source. If i designates the mag
rent magnetization ‘within the zone of high sat15 urations, but has the disadvantage that test pieces
of great weight must be employed. Besides, various bridge methods have been at ‘the same time
contrived for which test pieces of small weight
inay be employed. However, these methods re-
netizing current, 1111 the number of the turns of
the primary Winding, wz that Of the Secondary
winding, 6 the induced Secondary E- M- F" qr the
cross-section of the test piece in m2 and 1m the
mean path of the lines of force in cm the fol
lowing results are then Obtained!
20 quire a. very complicated ‘test equipment without
“
meeting the exacting conditions of an alternate
ing-current apparatus for testing iron. The
20
£Z=LiQ
'8"
greatest disadvantage of the bridge methods‘lies
above all in the fact that with. bridge methods
Bmx=
25 hitherto known the measurement is not effected
e ' 10
Gauss
222 - qr - WI
_B,,,,,
with sinusoidal voltage but with sinusoidal cur-
25
‘In
rent, so that a squeezed or‘ pointed ?ux curve
.
unavoidably
results. The wrong
test readings
owing to are,
the eddy
consequently,
current
30 component of- the higher harmonics in the ?ux.
-
i
.
A
The ex ressmn
Hw=0-4' - T' p
._
30
J5
cm
corresponds in meaning to the otherwise usual
expression"‘ampere windings per centimeter of
The invention has for its object to provide an
apparatus which eliminates the above-mentioned
drawbacks of the alternating-current apparatus
heretofore known for testing iron, 'i. e., such an
35 apparatus which ful?lls all conditions of a cyclic
core lengt .” The expression Binax indicates the
maximum induction. The expression a desig
magnetization without presenting the drawbacks
or restrictions of the aforesaid apparatus.
An apparatus of the above-indicated character
may be manufactured without considerable ex
nates the permeability, Heft the. magnetization
actually present.
In the last formula the index i.
“e?” is suitably added,' not to cm, but to ‘A, as
only the value A is variable.
40
40 penditure, if means are provided to ensure in-
v dependently of the size of, the test pieces the
natural magnetization up to the saturation, i. e.,
The manner in which the measurement is ef
fected must, consequently, ful?ll the condition
of a natural magnetization, i. e., the magnetiz
tain in‘ the test piece the sinusoidal voltage ing
current must be table toassume that curve
45 throughout the entire measuring range.
which produces a sinusoidal ?ux in con 45
In the accompanying drawing, Fig. 1 is a dia ‘shape
gram illustrating the principle of my invention; nection with the hysteresis character of the
Fig. 2 is a diagram showing the relation between
In order to meet the above requirement it is.
current, magnetic ?ux, and induced voltage, and
Fig. 3 is a diagram of an apparatus embodying essential that apart from the test piece, there
if conditions are made to cause the flux to main- -
material.
to
my invention.
-
.
For a better understanding of the individual
measures required for carrying out the inventive
idea Fig. 1 of the accompanying drawing shows
diagrammatically in principle the simplest form
,
'
_
be practically no other linear or non-linear re 50
sistances in the primary circuit. The internal
. losses of the 'ammeter must be, therefore, very
small as compared to the'magnetization e?’ect of
the. test piece. ‘This condition may be ful?lled
if a highly sensitive direct-current measuring 65
2,184,589
2
instrument with series recti?er is employed for “succession is, consequently, re?ected by the same
in two planes perpendicular to each other and
measuring the current. Furthermore, the gen
erator supplying the magnetizing current and may indicate on a surface scale the relationship
insulating at the same time the instrument from between both values which in?uence the position
of the mirrors. The measuring loops of such an
the supply circuit must have a small total im
indicating or recording apparatus are connected
nitude may be connected in parallel relation to according to the invention to the primary cir
the generator. Furthermore, the internal losses cuit or to the secondary circuit of a piece of the
of the voltmeter connected to the secondary side magnetizable material under test in such a man 10
10 must also be small, in order that the secondary ner that ‘the one mirror deflects in accordance
winding may not react on the primary circuit, and with the instantaneous intensity of the exciting
in order that the secondary voltage measurement current and the other mirror de?ects in accord
may approach. as far as possible the pure E. M. F. - ance with the instantaneous density of the ?ux.
measurement. This may be accomplished also Since the ?ux cannot-be directly measured the
induced voltage is instead thereof measured ac 15
15 by the use ‘of a highly sensitive direct-current cording to the invention. Since, however, the
measuring instrument with series-connected rec
ti?er. Finally, it is essential that the greatest ?ux and the secondary voltage are 90° out of
possible cross-section of the conductors be chosen phase, the values of the induced secondary volt
pedance. , To this end, a capacity of suitable mag
so as to maintain the ohmic resistances of both
20 circuits at a very low value.
.
Brie?y stated the following result is obtained:
The impedance may be practically fully com
pensated for by a parallel condenser. A highly
sensitive direct-current measuring instrument
25 has internal losses of about 0.1 . 10“8 watt. If
an e?fect of 10 . 10-‘6 watt, 1. e. hundred times
age leading 90° are measured as such values
which correspond to the instantaneous values of 20
current. This substitution of the instantaneous
values of the induced voltage for‘those of the
flux may be easily effected in the case of a sinu
soidal behavior of the voltage, since in this case
25
also the?ux varies sinusoidally.
To measure the instantaneous values of the
the amount of an instrument, is substituted for current or of the induced voltage any of the ar
both instruments inclusive of the series and shunt rangements hitherto known such as, for instance, '
resistances thereof and if the condition is made Joubert discs or instead thereof vibrating contact
' synchronous switches with separate excitation, 30
30 to cause this effect to amount only to 1% of the for instance as described in Patent No. 1,931,267
magnetization effect of the test piece in order .to
attain a natural magnetization, a magnetization to H. Pfannenmuller, may be employed. For in
stance, also independently controlled dry recti
effect in iron of l mva. results.
‘
A simple calculation shows that this amount ?ers may be employed.
In order to plot predetermined points of the 35
85 may be attained for a magnetic flux density hysteresis loop the measurement must be based
B=vl0 in the case of normal sheet irons having
within a full period on a series of instantaneous
as test pieces only a weight of 10 g. It is, con
values of the current curve. To this end, an
sequently, possible to carry out accurate alter
nating current measurements with test pieces ordinary phase shifter having a range of 360° is
40 having a very small weight, if the above-men
tioned rule is adhered to. In practice, however,
the conditions are still far more favorable, since
the above-indicated ?gures refer to the complete
de?ection of the instrument and since the mag
netization is besides effected within the zone of
the initial permeability with sinusoidal current
and voltage curves so that the extreme ratio of
the instrument effect to the magnetization effect
need not be maintained. In those zones of the
magnetizing curve in which this ratio is impor
'50 tant, i. e. from about 15 to 20% of the induction
in the zone of saturation, the magnetization
effect is higher by 102 to 103 so that the natural
magnetization is at all events ensured. In prac
tice the measurement of a test piece of 10 g. in-.
employed by means of which a synchronous mo
tor is fed when using Joubert discs.
By the use of independently controlled oscil
lating or static recti?ers the exciting voltage of '
these recti?ers is supplied by the phase shifter,
i. e., two voltages which are 90° out of phase are 45
tapped off in such a connection that for any ro
tation of the phase shifter the relative phase
position of ' both exciting voltages supplied by
the phase shifter remains una1tered._
The measurement of the induced secondary 50
voltage is only permissible, if the magnetization
is sinusoidal.
However, in the case of the above
A particularly convenient realization of the
described arrangement oscillating recti?ers are
employed at the secondary side which cause the
measuring instrument connected behind the same 55
to indicate a de?ection depending upon the arith
metical mean. Since according to the known
relation the arithmetical mean of the voltage cor
55 dependently of the quality of the material is,
therefore, possible.
~
above-described inventive idea results from the ' responds to the maximum value of the ?ux, the
60
consideration that all magnetical values of a
arrangement may be also employed, if the mag 60
material are based ‘on the hysteresis loop, and
that, therefore, the utilization of the inventive
idea for the design of an apparatus which enables
the recording of any points whatever of the hys
teresis loop represents a considerable advance
as to the testing of magnetizable materials, pro
vided that the apparatus is simple to manipulate.
netization is not sinusoidal.
To this end, a coordinate indicator or recording
rent and the dot-and-dash wave train illustrates
apparatus is employed according to the inven
70 tion, 1. e., an apparatus which indicates the re
lationship between two values on a surface scale.
Such an apparatus consists, for instance, of two
mirror galvanometers, whose axes of rotation of
the mirrors are perpendicular to one another.
A ray of light falling on the two mirrors in
‘
To explain the above, Fig. 2 shows the rela
tionship between the altemating-current mag
netic. flux and the ‘induced voltage._ The solid
curve represents the exciting current. The 65
dotted wave train represents the ?ux in the test
piece which is in phase with the energizing cur
the induced secondary voltage lagging the flux
by 90". Since the wave trains of the flux and 70
voltage are similar to each other in the case of
the sine shape, the ?ux may be replaced by the
voltage which'is capable of being measured di
rectly. The peak value of the current,‘ conse
quently, corresponds to the peak value of the 75
I
I
induced voltage.
2,184,589
the current is determined at the point designated
by A‘ at which the voltage and, therefore, valso
the flux pass the zero value, the instantaneous
value of the current corresponds to the coercive
force, where as at point B where the current has
decreased to zero, the voltage value measured cor
responds to the remanence.
_
~
10 in intersection of the hysteresis curve with the
axes'of ordinates and abscissae. Consequently,
if, for instance, only these values areto be de
termined the phase shifter may only be so ad-'
justed that in the case of the remanence meas- '
15 ureme'nt the instantaneous value of the induced
voltage andin the case of the coercive force
measurement the instantaneous value of the cur
rent become zero. The other ordinates indicate
thén the corresponding value of the coercive force
and of the remanence respectively.
Fig, 3 illustrates the diagram of connections of
an arrangement according to the invention. The
condenser C is connected across the leadswhich
connect the system to the alternating current
source. I denotes the recording surface. 2 and
3 are the loops and mirrors of both galvanom
eters. 4 is the luminous source from which a
sharply limited ray of light falls on the recording
35
surface i by the way of both-_mirrors 2 and 3.
5 is the iron test piece‘. 6 is the primary and ‘i
the secondary winding of this test piece. The
primary winding 6 is connected to the secondary
winding of a transformer 8 whose secondary
‘voltage may be adjusted at will. 9 denotes the
primary and ID the secondary winding system
of an induction regulator or phase-shifter.
mirror, a second revolvable mirror ‘ and means
connected in the secondary circuit for de?ecting
said second mirror, the axes of revolution of said
mirrors being perpendicular to each other, a light
source and a surface scale being arranged with
- respect to said mirrors so that a light beam com
The same values may be obtained by the points
'30
3
If the instantaneous value of _ nected in the primary circuit for de?ecting said
Two
phases 90° out of phase are tapped from the sec
ondary winding and serve to energize two sepa
rately controlled switching arrangements H and
40 I2. The synchronous switching arrangement ll
controls the connection’ between the primary
circuit 6 and the measuring loop 3 in such‘ a
manner that the same instantaneous values are
ing from said light source is re?ected successive
ly by said two mirrors onto said surface scale,
a separately excited synchronous switch arranged 10
in said primary circuit for periodically interrupt
‘ing said circuit, a second separately excited syn
chronous switch arranged in said secondary cir
cuit for periodically interrupting said secondary
circuit, and means for exciting said two‘switching 15
devices, said means being electrically coupled with
said current source and designed for exciting said
two switches with 90° phase displacement against
each other and with a certain phase position with
respect to the current of said current source, 20
whereby the instantaneous value of the primary
current acts on said means for de?ecting said
?rst-mentioned mirror and the instantaneous
value of the voltage induced in said secondary
windings acts on said means for de?ecting said 25
second mirror.
2. In an alternating current device for meas
uring magnetic properties of a test piece, in com
bination, a closed magnetic circuit, at least part
of which is the test piece, primary and secondary 30
windings on said magnetic circuit, an alternating '
current source connected in a‘ primary circuit
with said primary winding, impedance balancing
means connected in said primary circuit for com-1
pensating the impedance of said current source, a 35
revolvable mirror and means connected in the
primary circuit for'de?ecting said mirror, a sec
ond revolvable mirror and means connected in
the secondary circuit for de?ecting said second
mirror, the axes of revolution of said mirrors be
ing .perpendicular to each other,‘ a light source
and a recording surface being arranged with re
taken from each phase. ‘The synchronous switch
spect to said mirrors so that a beam coming from _
‘the secondary circuit ‘I of the test piece 5, how
ever, with the 'di?erence that the instantaneous
values obtained and the instantaneous value of
rately excited synchronous switch arranged in
said primary circuit for periodically interrupting
ing arrangement I! controls in the same manner ' said light source is re?ected successively by said
the current are 90° out of phase.
The galvanom
50 ' eters 2 and 3 constitute a. voltmeter and an em
meter respectively, and each of them is connected
in series with the recti?er forming part of the
two mirrors onto said recording surface, a sepa
said circuit, a second separately excited syn
chronous switch arranged in said secondary cir
cuit for periodically interrupting said secondary 50
circuit, and means for exciting said two switch
switching arrangement I! and II respectively.’ ing devices, said means being electrically coupled
'The zero point of the coordinate system on
the surface I’ is given byv the luminous point 4
which is projected by the deenergized galvanom
eter systems 2 and 3 ‘on'the recording surface.
‘ Insteadof this recording surface a screen may
be used which is designed preferably as an
60 opaque disc. The regulating transformer 8
serves to adjust the desired sensitiveness or the
desired induction. The range of measurement
of the arrangement may be adjusted at will by
the number of turns 6 and ‘I wound on the test
65
piece 5.
'
'
I claim as my invention:
1. In an alternating current device for meas
uring magnetic properties of a test piece, in com
bination, ‘a closed magnetic circuit, at least part
of which is’ the test piece, primary and secondary
‘is
with said current source and including a phase
shifter for producing a phase displacement of 90°
between the action of said two switches and a
phase position of this action with respect to said
current source at which the instantaneous value
of the primary current acts on said means for
de?ecting said ?rst-mentioned mirror and the
instantaneous valueof the voltage inducedin said 60
secondary windings acts on said means for de
?ecting said second mirror.
3. In an alternating current device for meas
uring magnetic properties of atest piece, in com
bination, a closed magnetic circuit, at least‘ part
of which is the test piece, primary and secondary
windings on said magnetic cincuit, an alternating
current source of negligible total impedance with
respect to the impedance of said primary winding,
said source being connected with said primary 70
windings on said magnetic circuit, an alternating
current source of negligible total impedance with
res act to the impedance of said primary winding,
sai source being connected-with said primary
said primary winding and having a rotatable mir
winding. a revolvable mirror and means con
ror as actuated member. a second highly sensitive
winding, a highly sensitive direct current meas- '
uring device connected in the electric circuit of
a
2,184,589
direct current measuring device connected in the
circuit of said secondary winding and having also
a rotatable mirror forming its actuated member,
a light source and a screen having a support com
6 mon with said two measuring devices, said devices,
said light source and said screen being arranged
on said common support so that the rotation axes
of said devices are perpendicular with respect to
each other and a beam coming from said light
source is reflected successively by said two mir
rors onto said screen, a separately‘ excited syn
chronous switch arranged in said primary cir
cuit for periodically interrupting said circuit, 2.
second separately excited synchronous switch ar
ranged in‘ said secondary circuit for periodically.
interrupting said secondary circuit, and means
for exciting said two switching devices, said
means including a phase shifter electrically cou
pled with said current source and designed for
supplying two exciting voltages of 90° phase dif
ference to said switches, whereby‘ said two
switches and said measuring devices connected
with said switches are actuated in accordance
with the current of said primary winding and the
voltage of said secondary winding respectively.
WILHEIM THAL.
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