Iwatsu SY-956 User manual

Instruction Manual
Mini Single Sheet Tester
SY-956

Ⓒ2014_2015 IWATSU TEST INSTRUMENTS CORPORATION．All rights reserved．

I
Introduction
◇Thank you for purchasing this IWATSU instrument and please regularly use Iwatsu instruments
lastingly in future.
◇Please read this manual before using this product, then keep the manual handy for future reference.
◇This instruction manual describes operating precautions, operating procedure, operation examples,
and specifications. For the main unit of the B-H Analyzer, please refer to its instruction manual.
Safety Precautions
To ensure safe operation of this product and to prevent injury to the user or damage to property, read and
carefully observe the warnings and cautions in the following sections
Definition of warnings and cautions used in this manual
Warnings
Incorrect operation or failure to observe the warning may result in
death or serious injury.
Cautions
Incorrect operation or failure to observe the caution may result in
injury or damage to instrument.
Notes
◇Parts of the contents of this manual may be modified without notice for improvements in specifications
and functions.
◇Reproduction or reprinting of the contents of this manual without prior permission from IWATSU is
prohibited.
◇All the product and brand names in this document are registered trademarks of their respective
companies and individuals, and are used here for identification purpose.
◇FINEMET®is a registered trademark of Hitachi Metals, Ltd. It shows as follows in this manual.
◇If any question about this product arises, contact Iwatsu at the address listed at the end of this manual
or our sales distributors.
History
◇June 2014: 1st edition
◇July 2015: 2nd edition
KML089721 A4-714020(N)

II
Read the following safety information. Read the next page.
Warnings
●Please be careful with the pole faces of the measuring
yoke.
The edges of the measuring yoke are not chamfered, in order to suppress leakage flux. Touching it
may result in injury (such as a cut on your hand).
●Do not use in an environment with explosive gases.
It may cause an explosion.
●If you notice smoke, foul odor or abnormal noise,
immediately power off this product and remove the
power plug from the receptacle.
Continued use under these circumstances may result in an electric shock or fire. Turn off the main
power switch on the front (〇side), and remove the power plug from the receptacle. Then contact
Iwatsu office or our sales distributors for repair. Do not attempt to repair this product yourself.
●Make sure no water gets on or inside this product.
Do not use this product if wet, otherwise an electric shock or fire could occur. If water gets on or
inside this product, turn off the main power switch on the front (〇side), and remove the power plug
from the receptacle. Then contact Iwatsu office or our sales distributors for repair.
●Do not place this product on an unstable support such
as shaky base or inclined plane.
Dropping or falling-down of this product could result in an electric shock, injury, or fire. If this product
is dropped or its cover is broken, turn off the main power switch on the front (〇side), and remove
the power plug from the receptacle. Then contact Iwatsu office or our sales distributors for repair.
●Do not expose this product to excessive vibration or
shock.
Dropping of falling-down of this product could result in injury.
●Dropping of this product could result in injury to your
body or damage to your property.
Before carrying this product, remove the measurement sample and cables, close the cover, and
then firmly hold it with both hands while carrying so that it does not fall.

III
Read the following safety information. Read the next page.
Warnings (Continued)
●Use 3-core power cord.
If not, an electric shock or failure may occur.
If power is supplied from the 2-wire receptacle using the 3-core/2-core conversion adapter,
connect the ground terminal of the 3-core/2-core conversion adapter to the ground.
If power is supplied from the 3-wire receptacle using the provided 3-core power cord, grounding is
made by the ground line of the power cord.
●Always use this product with a specified power supply
voltage.
If not, an electric shock, fire, or failure may occur. The range of operating voltage to be used is
stated on the rear panel.
This product runs on AC power supply of single-phase, 50/60Hz and AC100-240V.
No voltage selection is required, since this product automatically adapts to the power supply
voltage.
●Strictly observe items below when handling the power
cord.
If not, an electric shock or fire may occur. If the power cord is damaged, contact Iwatsu office or our
sales distributors for repair.
Do not modify the power cord.
Do not pull the power cord.
Do not forcibly bend the power cord.
Do not heat the power cord.
Do not twist the power cord.
Do not let the power cord get wet.
Do not bundle the power cord.
Do not put heavy objects on the power cord.
●Do not touch the plug of the power cord with wet
hands.
If not, an electric shock may occur.
●Do not make metal touch the blade of the power plug.
If not, an electric shock or fire may occur.
●Do not plug too many leads into a single receptacle.
If not, a fire or overheating may occur.
●If thunder sounds, remove the power plug of this
product from the receptacle and do not use it.
It causes an electric shock, fire or failure according to the thunder.

IV
Read the following safety information. Read the next page.
Warnings (Continued)
●Do not attempt to modify this product.
This may result in an electric shock, fire or failure. The user cannot repair this product. Do not repair
this product opening it. Also, requests to repair the unit may be refused if unauthorized modifications
have been made. Contact our sales distributors for repair. Please note not responding to the repair
when the open security seal is removed, the cover is opened or the product is modified.
●Do not use this product when being failed.
If not, an electric shock or fire may occur. For a failure, contact Iwatsu office or our sales distributors
for repair.
Do not place any small metal objects or containers
containing water or chemical on or near this product.
If liquid spills or a small metal object gets in, it may cause an electric shock, fire or failure. If
water/chemical/metal object gets in, turn off the main power switch on the front (〇side), and
remove the power plug from the receptacle. Then contact Iwatsu office or our sales distributors for
repair.
●Do not put any metallic material or inflammable object
through the ventilation port.
If any foreign object is put through the ventilation port, an electric shock, fire, or failure may occur. If
any foreign object enters this product, turn off the main switch on the front (〇side), and remove
the power plug from the receptacle. Then contact Iwatsu office or our sales distributors for repair.
●Do not put any object near to the ventilation port of
this product.
If not, heat accumulates inside this product, causing an electric shock, fire, or failure.
●Before inserting the power plug into the receptacle,
confirm no dust attached to it. In addition, remove the
power plug and adapter from the receptacle and
inspect/clean them once a half year or a year.
Dust may cause an electric shock, fire, or failure.

V
Read the following safety information. Read the next page.
Cautions
●Turn off the main power switch on the front before connecting or disconnecting the power
cord.
Connecting or disconnecting the power cord while the power switch is ON (I side) may result in an
electric shock or failure.
●Insert the power supply plug into the receptacle firmly.
If not, an electric shock, fire, or failure may occur.
●When disconnecting the power cord from the receptacle, pull it out by grasping the plug.
Do not pull on the cord itself, as doing so may damage the cord and could result in an electric
shock or fire.
●Before moving this product, confirm that external connection lines such as the power cord
and cables are removed.
The power cord and cable may be damaged causing a fire or electric shock.
●Never replace the fuse inside the main unit. Contact Iwatsu office or our sales distributors for
replacement.
●Use 3-core power cord in accordance with the power supply voltage.
If not, a fire may occur. In addition, if a 2-core power cord is used, a fire may occur.
Unless specified when purchasing this product, the power cord suitable for 100V system (center
voltage: 100V to 120V) is attached. If the power supply voltage is 200V system (center voltage:
200V to 240V), use 3-core power cord suitable for 200V system (optional) specified by Iwatsu
(rating voltage: 250V).
●Do not apply an excessive voltage or current to the input connector.
If not, a fire, electric shock, damage to this product or a sample, or failure may occur.
The maximum allowable input voltage and current are as follows:
Input connector
Maximum allowable input voltage or current
Between S2-S1
200V
POWER INPUT
200V / 6A
●Never touch the measuring yoke of this product with your bare hands.
The measuring yoke is made of FINEMET ®. Touching the measuring yoke may cause it to rust,
resulting in incorrect measurements.
●Do not measure a wet or dirty sample with this product.
The measuring yoke may rust or deteriorate, causing incorrect measurements.
●Do not measure a sample with an uneven surface or with foreign objects on its surface.
Pole faces of the measuring yoke or the press block may get damaged.

VI
Read the following safety information.
Cautions (Continued)
●Do not place any object on this product.
Otherwise, the cover may break and come in contact with the internal circuits, causing an electric
shock, fire, or failure.
●Always use this product only within the rated operating range.
If used over the rated range, failure may occur. The allowable range is as follows:
Only indoor use
Operating temperature: 5C to 35C
Operating humidity: no dew allowed below the moisture amount of 85 RH
(35C, non-condensation)
●Do not expose this product to direct sunlight or high humidity.
If not, heat may accumulate inside this product, resulting in a fire.
●Do not place this product in a location with excessive moisture or dust.
If not, an electric shock or fire may occur.
●Do not expose this product to oil smoke or steam; e.g. besides cooking table or humidifier.
A fire or electric shock may occur.
●Do not use any damaged cable or power cord.
Otherwise, an electric shock or fire may occur.
●If this product will not be used for a long time, remove the power plug from the receptacle for
safety.
●Before transporting, remove the measurement sample from this product, close the cover, and
then pack with the packing material provided at the time of purchase or the equivalent or
better.
Excessive vibration or shock applied to this product during transportation may cause it to
malfunction, resulting in a fire. The warranty will be voided when a failure or damage is caused by
transporting the product while the sample is attached or the cover is open.
If there is not a proper packing material/ shock absorber, contact Iwatsu office or our sales
distributors. When having this product transported by a shipping company, write "Precision
Instrument - Handle With Care" on each side of the packing box.
●When cleaning this product, remove the power plug from the receptacle for safety. Use dry
cloth to wipe water drops away.
If not, an electric shock or fire may occur.

VII
Checking packed materials
When receiving this product, check the packed materials referring to components below (for the open bale
chart, see the next page). If there is a lacked item or an item damaged during transportation, immediately
contact Iwatsu office or our sales distributors.
Components
Mini Single Sheet Tester SY-956 main unit............................1
Accessories
Mini Single Sheet Tester cable (SY-957)..........................1
B Coil 01 (SY-958) ............................................................1
B Coil 02 (SY-959) ............................................................1
Thumbscrews for the terminal block .................................2
Tweezers...........................................................................1
Blower brush .....................................................................1
Accessories storage box...................................................1
Power cord........................................................................1
Cord strap..........................................................................1
Instruction manual.............................................................1

VIII
Open bale chart (main unit and accessories)
Management of product
When disposing of this product, it is necessary to recycle or dispose of it properly in accordance with a
local law or regulation. When disposing of it, request a recycle company to dispose of it in accordance with
a local law or regulation
Repair and shipment of the product to be repaired
If a failure occurs, mail this product to our service center. Any failure which occurs within the term of
warranty and for which Iwatsu is responsible should be repaired without any cost.
When shipping a product to be repaired, clearly write the product name, serial number (in the label on the
rear of this product), description of the failure, and name, division, and telephone number of the
responsible person.
About the open security seal
A security seal is affixed on the main unit. (Refer to ■3.3 Rear panel.) We do not accept any repairs
orders for the product if the security seal is broken.
Accessories sleeve
SY-956 main unit
Outer packing box
(cardboard box)

1
Table of Contents
Chapter 1 Introduction ...............................................................................................................................................2
■1.1 Summary........................................................................................................................................................2
■1.2 Features.........................................................................................................................................................2
■1.3 Cautions for handling and installation............................................................................................................3
Chapter 2 Before Measurement.................................................................................................................................4
■2.1 For proper measurement...............................................................................................................................4
■2.2 Differences in measured values among Epstein frame, conventional SST, and this instrument...................5
■2.3 How to find the detection limit........................................................................................................................6
■2.4 Regarding air-gap compensation coils ..........................................................................................................6
■2.5 Measurement principles.................................................................................................................................7
Chapter 3 Names and Functions of Each Part.......................................................................................................11
■3.1 Front panel...................................................................................................................................................11
■3.2 Fixture..........................................................................................................................................................12
■3.3 Rear panel....................................................................................................................................................13
Chapter 4 Measurement...........................................................................................................................................14
■4.1 Flow before measurement...........................................................................................................................14
■4.2 Connecting equipment.................................................................................................................................15
■4.3 Connecting Mini Single Sheet Tester Cable SY-957....................................................................................16
■4.4 Powering on.................................................................................................................................................18
■4.5 Powering off.................................................................................................................................................18
■4.6 Attaching and detaching a B Coil.................................................................................................................19
■4.7 Measurable samples....................................................................................................................................20
■4.8 Setting a sample ..........................................................................................................................................21
■4.9 Confirmation of functions .............................................................................................................................22
■4.10 Selecting single sheet testing mode ..........................................................................................................22
■4.11 Confirming POD.........................................................................................................................................22
■4.12 Measurement screen.................................................................................................................................23
■4.13 Input/selection of sample constant ............................................................................................................24
■4.14 Setting measurement conditions................................................................................................................25
■4.15 Measurement.............................................................................................................................................26
■4.16 Switching graphs........................................................................................................................................28
■4.17 Cursor measurement.................................................................................................................................28
■4.18 Scaling up/down of graph ..........................................................................................................................28
■4.19 Reference function.....................................................................................................................................28
■4.20 USB memory output of screen hardcopy...................................................................................................28
■4.21 Save/Read data .........................................................................................................................................28
Chapter 5 Maintenance ............................................................................................................................................29
■5.1 Daily maintenance .......................................................................................................................................29
■5.2 Calibration....................................................................................................................................................29
Chapter 6 Specifications..........................................................................................................................................30
■6.1 Specifications...............................................................................................................................................30
■6.2 Outside appearance diagram.......................................................................................................................31
■6.3 Outside appearance of the fixture................................................................................................................32

2
Chapter 1 Introduction
This instruction manual explains only about those functions of the B-H Analyzer that are added by operation
and use of a Mini Single Sheet Tester SY-956. Descriptions of the functions that overlap with the standard
functions equipped with the B-H Analyzer are omitted. Please refer to the B-H Analyzer’s instruction manual.
■1.1 Summary
●In combination with the B-H Analyzer, this instrument allows users to measure core loss of a single sheet
sample.
* Not compatible with B-H Analyzers SY-8232, SY-8217, and SY-8258.
■1.2 Features
●The following are the features of this instrument.
(1) This instrument employs vertical single-yoke type, magnetizing current (MC) method-based single sheet
testing (similar to IEC 60404-3).
(2) FINEMET®with a small core loss and magnetostriction is used for the measuring yoke.
(3) Highly accurate measurement of single sheet core loss has been achieved by providing the Yoke
Compensation.*1 function, which cancels the measurement yoke’s magnetic properties, such as core
loss.
*1: A joint patent application with Professor Toshihisa Shimizu of Tokyo Metropolitan University has
been submitted for this function. This function may not work under the measuring conditions in which
a core loss of a yoke is small.
(4) Measurement frequency is a sine wave between 10 [Hz] to 20 [kHz], which is one of the widest
frequency ranges in the world for a Single Sheet Tester (SST).
(5) Capable of measuring a single sheet sample that is far smaller than what was possible before. Measurable
size is width 35 mm or less, length 36 mm or more, and thickness 3 mm or less (1 mm or less when a
provided B coil is in use).
(6) A semi-automatic slider, which presses the sample at a constant pressure, is provided, in order to improve
measurement reproducibility.

3
■1.3 Cautions for handling and installation
●Do not touch the measuring yoke of this instrument with your bare hands.
The measuring yoke is made of FINEMET®. Touching the measuring yoke with your bare hands may cause
it to rust, resulting in incorrect measurements.
●Please be careful with the edges of the measuring yoke’s pole faces.
The edges of the measuring yoke are not chamfered, in order to suppress generation of leakage flux.
Touching it may result in a cut on your hand.
●Do not measure a wet or dirty sample with this instrument.
The measuring yoke may rust or deteriorate, resulting in incorrect measurements.
●Do not measure a sample with an uneven surface or with foreign objects on its surface with this
instrument.
Pole faces of the measuring yoke or the press block may get damaged.
●Use this instrument within a specified range of temperature and humidity.
If exposed to direct sunlight or used outside an operating range, e.g., high humidity, it may fail.
Ranges of temperature and humidity for usage are as follows:
■ Indoor use only
■ Operating temperature: +5C to +35C
■Operating humidity: no dew allowed below the moisture amount of 85 RH (+35C, non-condensation)
●Do not place this instrument in a location with excessive moisture or dust.
Placing it in a location with excessive moisture or dust may cause an electric shock or fire.
●Do not place an object on this instrument.
If an object is placed on top of this instrument, parts such as the cover may get damaged.
●Do not place an object near the ventilation port of this instrument.
Placing an object near the ventilation port may cause accumulation of internal heat, resulting in an electric
shock, fire, or failure.
●If this instrument falls, the impact may inflict bodily harm or cause damage to property. Before carrying,
remove all the cables, and then firmly hold with both hands while carrying so that it does not fall.

4
Chapter 2 Before Measurement
There are several points users need to know before taking measurements with this instrument.
■2.1 For proper measurement
●In order to correctly measure and evaluate samples made of a variety of materials, there are things to be
aware of other than excitation conditions.
(1) Conduct a comparative measurement with samples of the same shape (size).
Distribution of magnetic flux density in an excited sample is known to change not only with changes in the
manufacturing process of the samples but also with changes in the sample shape (size). Warpage of a sample
also needs attention, as it affects the air gaps against the yoke.
The following is an example of the geometry dependence of samples, as researched in our company.
[Measurement Examples of Geometry Dependence]
Figure 2-1 shows a B-H carve of a 0.1t×5.0w×107L
permalloy band (See Fig. 2-2).
The blue curve shows results when the band was an
oval. The yellow curve shows results when the band was
a circle.
This shows how the saturation magnetic flux density
changes drastically when the shape changes.
This measurement result also possesses reversibility.
Fig. 2-1 Geometry dependence of a B-H curve
Fig. 2-2 Permalloy band
(2) Conduct a comparative measurement, using the same B (magnetic flux density) coil.
Although 2 types of B coils are provided with this instrument, it is the best practice for users to wind a B coil by
themselves with consideration to the following (a) to (c):
(a) Always use the same wire for winding.
Eddy current loss generated in the windings by the yoke’s leakage flux may change when the size of the wire
changes.
(b) Always wind the same number of turns at the same location on the sample.
B to be measured is equivalent to the average magnetic flux density at the location of turns. Therefore, when
the location of turns on a B coil is changed, B may change even with the same sample, as magnetic properties
differ depending on the location of the sample. Similarly, when the number of turns is changed, B may change
even with the same sample, as changing the number of turns is equivalent to changing the testing location.
(c) Always wind tightly around the sample without overlapping.
If air-gaps are formed between the sample and the winding, correct measurement may become impossible, as
leakage flux is interlinked with the gaps of turns. The influence of the gaps is more prominent when the
permeability of a sample is low.
These considerations apply to the 2 provided B coils with different numbers of turns and hole sizes. Use the
same B coil when conducting a comparative measurement.
The example below shows the influence of air gaps, using our B Coil.

5
[Measurement Example of the Influence of Air-Gaps]
Figure 2-3 shows a B-H curve of a 0.35t×3.0wferrite slab.
The blue curve shows the measurement of a B Coil with
the hole size of 32.5 [mm2]. The yellow curve shows the
measurement of a B Coil with the hole size of 82.5 [mm2].
This shows how the saturation magnetic flux density and
amplitude permeability change due to the influence of the
air-gaps between the sample and the winding of the B
coils.
The influence of the air-gaps is particularly more
prominent when the permeability gets lower.
Fig. 2-3 Influence of the air-gap on B-H curves
(3) Pay attention to the front and the back of the sample when conducting a comparative measurement.
Some samples may have different magnetic properties in the thickness direction. Just to be sure, test both the
front and back under the same condition and make sure there is no significant differences in the measurement
results. Exercise extra caution when using thick samples.
(4) Conduct a comparative measurement by placing samples at the same spot on the yoke.
The location on the yoke where the sample is placed may change the internal distribution of magnetic flux
density when the sample is excited, depending on the permeability of the sample. It is the best to align the
centers of the width direction of a sample and the yoke.
Place the sample straight between the pole faces of the yoke; do not place it diagonally. Placing the sample
diagonally may change the magnetic path length and distribution of magnetic flux density within the sample.
(5) Conduct a comparative measurement with the same pressure.
Firmly press on the yoke the samples that cause magnetostrictive vibration. Otherwise correct measurements
may not be possible, as the vibration moves the sample or air-gaps between the yoke and the sample while
measuring.
(6) Conduct a comparative measurement under the same temperature.
It is a basic practice to conduct a comparative measurement under the same temperature, as magnetic
properties of some materials, such as permeability, may change with temperature.
Exercise extra caution when using ferritic materials, as their permeability changes, particularly around room
temperature.
■2.2 Differences in measured values among Epstein frame, conventional SST, and this
instrument
In short, the values measured by each device are never the same, although there are correlations between
the values. The same applies with the differences between measured values of an Epstein frame and a
conventional SST. This is because the magnetic field strength and distribution of the magnetic flux density
within a sample are thought to be different for each testing device even when measurements are collected from
the same sample under the same excitation conditions.
Cross sectional areas of the four corners of a sample, which overlap and form a closed magnetic circuit, differ
from the cross sectional area of the other parts in an Epstein frame. Air-gaps are formed also in these four
corners. Furthermore, the magnetic field strength and the distribution of the magnetic flux density within a
sample are thought to be non-uniform, because magnetic flux tends to pass through the inside of a sample
forming the closed magnetic circuit, where magnetic resistance is low.
Unlike the case of an Epstein frame, a sample does not overlap in a SST, but the air-gaps are still formed on the
yoke’s end face where it comes into contact with the sample.
Four of these areas exist in a double-yoke type tester and two in a single-yoke type tester.
Therefore, the magnetic field strength and the distribution of the magnetic flux density differ between the center
and the areas closer to the yoke.
This applies to both double- and single-yoke type testers.
Of course, although the values may differ, the measured values of each device are thought to correlate with

6
each other, if each measurement device is ideally tuned. For example, it is implausible that a sample that
shows the highest core loss with one type of measurement device shows the lowest core loss with another type
of device.
In order to conduct accurate measurement, it is important to use a testing device with high measurement
accuracy. In addition, as described in (1) to (6) of 2.1, it is also important to keep the measurement conditions
constant.
■2.3 How to find the detection limit
It was noted in the previous chapter that even when ideally tuned measurement devices, with different methods,
test the same sample under the same excitation conditions, the resulting values are never the same.
Thus, finding the detection limit of a device, as in the precision of the measurements derived from a specific
device, is of the utmost interest. There is an easy trick to find out; this trick may also work with an Epstein frame
and a SST. The trick is to take a measurement with no sample. In other words, use an air core coil that has only
air inside the winding. The coil needs to be the actual coil used for the measurement.
What to measure with an air core coil?
The easiest is the core loss Pcv. With an ideal core coil, there should not be any core loss.
Therefore, without any samples, ideal core loss is Pcv=0 and the area enclosed by the B-H curve is 0.
In reality, even without any samples, Pcv is not 0, because of the eddy current loss generated on the winding of
a B coil, due to a leakage flux, or the core loss generated at the measuring yoke in the case of SSTs. As such,
Pcv measured without any sample is the detection limit of core loss Pcv of the particular device with the same
frequency under the same excitation conditions. That means the samples with core loss smaller than this value
of Pcv cannot be measured.
■2.4 Regarding air-gap compensation coils
Some Epstein frames and the ordinal SSTs are equipped with an air-gap compensation coil. This coil is meant
to cancel out the added air-gap flux between a B coil and a sample. However, this method does not cancel out
the air-gap flux correctly.
This kind of air-gap compensation coil is not attached to the location of the B coil is. As mentioned in 2.1, the
value of B changes with the position of the B coil with respect to the sample. This is because the magnetic flux
density within the sample is non-uniform throughout the sample in both an Epstein frame and a SST. Therefore,
the air-gap flux generated between the B coil and the sample is thought to differ from the air-gap flux generated
in an air-gap compensation coil that is attached away from the B coil.
In addition, an air-gap compensation coil does not take the cross-sectional area of the sample into
consideration. Because the hole size of an air-gap compensation coil is the same as that of a B coil, an air-gap
compensation coil may cancel out the leakage flux crossing an air-gap larger than the air-gap between a B coil
and the sample.
This instrument is not equipped with an air-gap compensation coil. One reason is the extreme difficulty of
equipping an air-gap compensation coil that works well with different shapes of single sheet that this instrument
can test. The main reason is the inherent problems with the ordinary air-gap compensation coils.

7
■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.).
Ajoint 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 Ay, Relative permeability μy), equipped with an excitation coil (Number of turns n1)
and a B coil (Number of turns n3); similarly, a double-yoke (Core area Ay, Relative permeability μy), equipped
with an excitation coil (Number of turns n1) and a B coil (Number of turns n3); a signal generator that sends
excitation current to each excitation coil; and a shunt resistor (Resistance value Rs) 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. Asample single sheet (Core area
Ap, Relative permeability μp) is placed on top of the measuring yoke and wound with the B coil (Number of turns
n2).
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 i1a to the excitation coil on the
measuring yoke. This excitation current i1a is converted into a voltage V1a with the shunt resistor. At this time,
induced voltage V2is generated at both ends of the B coil of the single sheet.
When the magnetic path length of a single sheet is Lp, the magnetic field strength of the single sheet is Hp,
magnetic path length of the measuring yoke is Lya, and the magnetic field strength of the measuring yoke is Hya,
according to Ampere's law,
(1).
When a new magnetic field strength Hvis defined in formula (1) as follows:
(2),
formula (1) turns into (3).
 
󰇫󰇧
󰇨󰇬
󰇫󰇧
󰇨󰇬
 

8
Therefore, Hvis
(4).
Magnetic flux density Bpinside a single sheet is
(5).
A conventional MC method-based SST is equivalent to measuring the iron loss P per unit volume of a single
sheet from this Hvand Bp. (Whenever “iron loss” is indicated hereafter, it mean iron loss per unit volume.)
Because iron loss P is determined by dividing the area of the B-H curve by the cycle of the excitation signal,
(6),
when formula (2) is substituted into this, it becomes
(7).
The first term of formula (7) is the actual iron loss Pp, which only includes the magnetic field strength Hpand the
magnetic flux density Bpin a single sheet. The second term is related to the iron loss Hya in the measuring yoke,
which includes the magnetic field strength in the yoke. A conventional MC method-based SST ignores the
second term of formula (7) by assuming that the magnetic field strength in a measuring yoke Hya is small
compared to the magnetic field strength in a single sheet Hp(Hv≈Hp) in formula (2).
With this instrument, magnetic field strength in the measuring yoke Hya, which was unmeasurable with
conventional MC method-based SSTs, can be calculated from this 1st measurement and the 2nd and 3rd,
explained later. Using the value of Hya, find the magnetic field strength Hpof the single sheet and then calculate
the actual iron loss Ppof the single sheet with only the first term of formula (7).
In the 1st measurement, Hvand Bpare calculated by formulas (4) and (5).
The 2nd measurement is explained next.
Reconnect Relay 2 to iii-side. Do not change Relays 1 and 3. From the signal generator, send an excitation sine
wave signal of the same frequency f (cycle T) used in the 1st measurement so that the excitation current i1a2,
which flows through the excitation coil on the measuring yoke, is the same as the excitation current i1a from the
1st measurement. At this point, an induced voltage V3a is generated at both ends of the B coil on the measuring
yoke.
Magnetic flux density Bya in the measuring yoke is
(8).







   



 󰇫󰇧 󰇨󰇬  



   


 󰇧 󰇨   


 


9
Since the excitation current sent through the excitation coil of the measuring yoke is the same for the 1st and
2nd measurements; Bya derived in the 2nd measurement is, in fact, the magnetic flux density of the magnetic
field strength Hya in the measuring yoke from the 1st measurement.
Finally, the 3rd measurement is explained next.
Reconnect Relay 1 and 3 to b-side. From the signal generator, generate an excitation sine wave signal of the
same frequency f (cycle T) used in the 1st and 2nd measurements, and send the excitation current i1b to the
excitation coil on the double-yoke this time. This excitation current i1b is converted into a voltage V1b with the
shunt resistor. At this point, an induced voltage V3b is generated at both ends of the B coil on the double-yoke.
This excitation current i1b, which is sent through the excitation coil on the double-yoke, needs to be adjusted so
that the magnetic flux density Byb in the double yoke is the same as the magnetic flux density Bya in the
measuring yoke obtained in the 2nd measurement. In reality, i1b is adjusted so that Byb and Bya match within the
Tolerance set in the measurement conditions.
Magnetic flux density Byb in the double-yoke is
(9).
When the magnetic path length of the double-yoke is Lyb, the magnetic field strength Hyb in the double-yoke can
be calculated from Ampere’s Law:
(10).
Hyb is the magnetic field strength when the magnetic flux density in the double-yoke is Byb. This Byb is also the
same as the magnetic flux density Bya in the measuring yoke from the 1st measurement, and thus, Hyb turns out
to be the same as the magnetic field strength Hya of the measuring yoke from the 1st measurement. This is
because the B-H curve, which shows the relationship between magnetic field strength and magnetic flux
density, is the same for both the measuring yoke and double yokes of the same shape and material
composition.
Therefore, formula (10) can be written as
(11).
By modifying formula (2), the magnetic field strength Hpof the single sheet can be calculated as
(12).
Therefore, by applying Hvderived from the 1st measurement and Hya(=Hyb) derived from the 2nd and 3rd
measurements into formula (12), the magnetic field strength Hpof a single sheet at the time of the 1st
measurement can be obtained. The graph showing the relationship between this magnetic field strength Hpof
the single sheet and the magnetic flux density Bpof the single sheet derived from formula (5) is the B-H curve of
the sample single sheet.
 

 

 

  

󰇧
󰇨

10
In conclusion, by substituting Hpof formula (12) into the first term of formula (7),
(13),
the actual iron loss of only the single sheet Ppcan be calculated.
Yoke Comp. comes into effect when Yoke Comp. is Enabled, as explained in 4.15. When Yoke Comp. is
Disabled, testing is completed after the 1st measurement.
Still, Yoke Comp. does not necessarily work at all times. In order to make the magnetic flux density Bya of
the double-yoke in the 3rd measurement equal to the magnetic flux density Bya of the measuring yoke in the
2nd measurement, this instrument controls the amplitude of the signal generator precisely and adjusts the
excitation current i1b sent through the double-yoke. However, the generator cannot be controlled when this Bya
is extremely small. When a warning message is displayed and the 3rd measurement does not proceed after the
2nd measurement, it is usually the case that this Bya is extremely small (i.e., measurement conditions are such
that the core loss related to the measuring yoke is extremely small).
Fig. 2-4 Summary of the measurement principles

   



Signal
generator
Shunt resistor
Relay 1
B Coil
Single sheet
Excitation
coil
Measuring yoke
Double-yoke
Relay 2
Relay 3
B Coil
B Coil
Excitation
coil