Iwatsu SY-956, Инструкция по эксплуатации

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2.5 Measurement principles
Fundamentally, this instrument employs vertical single-yoke type, magnetizing current (MC) method-based
single sheet testing.
The biggest drawback of a conventional MC method-based SST has been the
inclusion of the measuring yoke-related core loss in the core loss of a sample. In other words, a
conventional MC method- based SST measures the properties of a soft magnetic composite material core that
is made up of 2 materials: the sample itself, and the yoke.
When the core loss of a yoke is sufficiently smaller than the core loss of a sample, the yoke-related core loss
can be ignored. However, there was no way of knowing the amount of this yoke-related core loss with a
conventional MC method-based SST. FINEMET
®
with an extremely small core loss is used for the measuring
yoke of this instrument. In addition, this instrument is equipped with the function to extract only the
sample’s
magnetic properties, such as core loss, from the soft magnetic composite material core that is made up of 2
materials, the sample and the yoke, by cancelling the yoke-related core loss. This function is called
Yoke
Compensation ( Yoke Comp. ).
A joint patent application with Professor Toshihisa Shimizu of Tokyo Metropolitan University has been submitted
for this Yoke Comp. function. A summary of the Yoke Comp. is explained below.
First of all, the composition of this instrument is as follows. As shown in Fig. 2-4, this instrument is composed of
a measuring yoke (Core area A
y
, Relative permeability μ
y
), equipped with an excitation coil (Number of turns n
1
)
and a B coil (Number of turns n
3
); similarly, a double-yoke (Core area A
y
, Relative permeability μ
y
), equipped
with an excitation coil (Number of turns n
1
) and a B coil (Number of turns n
3
); a signal generator that sends
excitation current to each excitation coil; and a shunt resistor (Resistance value R
s
) that converts the excitation
current into a voltage. The measuring yoke and the double-yoke are made of the same FINEMET
®
. The
double-yoke is hidden inside the casing.
Also provided is Relay 1, which switches the excitation coil through which an excitation current is sent, and
Relays 2 and 3, which switch the B coil, which measures an induced voltage. A sample single sheet (Core area
A
p
, Relative permeability μ
p
) is placed on top of the measuring yoke and wound with the B coil (Number of turns
n
2
).
Yoke Comp. is achieved by dividing the measurement into 3 repetitions . The 1st measurement is
explained first. The number of the current measurement repetition is shown in magenta color on the graph on
the Measurement screen of the B-H Analyzer.
Connect Relay 1 to the a-side, Relay 2 to the ii-side, and Relay 3 to the a-side. Send an excitation signal of a
frequency f (cycle T) from the signal generator and send an excitation current i
1a
to the excitation coil on the
measuring yoke. This excitation current i
1a
is converted into a voltage V
1a
with the shunt resistor. At this time,
induced voltage V
2
is generated at both ends of the B coil of the single sheet.
When the magnetic path length of a single sheet is L
p
, the magnetic field strength of the single sheet is H
p
,
magnetic path length of the measuring yoke is L
ya
, and the magnetic field strength of the measuring yoke is H
ya
,
according to Ampere's law,
(1).
When a new magnetic field strength H
v
is defined in formula (1) as follows:
(2),
formula (1) turns into
(3).
n
1
i
1a
= H
p
L
p
+ H
ya
L
ya
= {H
p
+ (
L
ya
L
p
) H
ya
} L
p
H
v
= {H
p
+ (
L
ya
L
p
) H
ya
}
n
1
i
1a
= H
v
L
p