Data 5

Final Report by Power Transformers Evaluation
Standards Subcommittee, Energy Efficiency Standards
Subcommittee of the Advisory Committee for Natural
Resources and Energy

December, 2011
Ministry of Economy, Trade and Industry

As regards power transformers, evaluation standards for manufacturers orimporters of transformers (hereinafter referred to as “manufacturers, etc.”)
were presented in the final report prepared by the Power Transformers
Evaluation Standards Subcommittee, Energy Efficiency Standards
Subcommittee of the Advisory Committee for Natural Resources and Energy(April 3, 2002), and oil-immersed transformers reached the target fiscal year in
FY2006 and encapsulated-winding transformers did so in FY2007.
To study new target standard values, etc. for oil-immersed transformers andencapsulated-winding transformers, the “Power Transformers Evaluation
Standards Subcommittee” was established at the 14th Energy Efficiency
Standards Subcommittee (December 24, 2009) and evaluation standards, etc.
for manufacturers, etc. of transformers (the scope of transformers to be covered,categories of transformers, target standard values, measurement methods,
items to be indicated, etc.) were studied and the interim report was prepared asfollows.
Note that this report addresses only the transformers covered by the study so
far conducted, and pole transformers are to be studied hereinafter by thisSubcommittee.

1. Evaluation of current standards [See Reference 2.]
As regards the oil-immersed transformers which reached the target fiscal
year in FY2006, a weighted average value of energy consumption efficiency
calculated with the number of units shipped is 636 W, while that of theencapsulated-winding transformers which reached the target fiscal year in
FY2007 is 1,350 W.
Accordingly, an improvement of energy consumption efficiency based on thenumber of units shipped in the target fiscal year is 711 W which is a weighted
average value of transformers as a whole, realizing improvement by 13.1% froma weighted average value (818 W) of energy consumption efficiency calculated
based on the number of units shipped before the Top Runner standard isintroduced (products shipped in FY1999).
Although the achievement falls below the estimated value (570W) as well as
the estimated improvement (30.3%) which must have been achieved if the Top
Runner standard are achieved, it is because the transformers adopted byfacilities shift from those with smaller capacity to those with larger capacity inrecent years. Specifically, in case of oil-immersed transformers, the averagecapacity is increased from 147 kVA in the period from FY1996 to FY2000 to 206
kVA in FY2008; and in case of encapsulated-winding transformers, the averagecapacity is increased from 283 kVA in the period from FY1997 to FY2001 to 392
kVA in FY2008.
1

If evaluated based on the improvement ratio by rated capacity which
excludes the effect of large capacity, the improvement ratio of energy
consumption efficiency is 34.0% for oil-immersed transformers, 26.8% forencapsulated-winding transformers and 32.8% for transformers as a whole.
Therefore, it can be said that the energy efficiency of each capacity is making
progress as a result of energy saving efforts made by manufacturers, etc. andthe current standards based on the idea of Top Runner method can beevaluated as working effectively.
Table 1:

Achievement of obligations to improve energy saving performanceof transformers

Type ofequipment

Target fiscal
year

Achievement
value of energy
consumption
efficiency(Base fiscal year)

Transformers

FY2006(Oil-immersed)
FY2007(Encapsulatedwinding)818 W/unit(FY1999)

Estimated
improved valueof energy
consumption
efficiency(Improvement
ratio)

Achievement
value of energy
consumption
efficiency intarget fiscal year
(Improvement
ratio)

570 W/unit(30.3%)

711 W/unit(13.1%) *1(32.8%) *2*1 Weighted average*2 Simple average
Note 1) The estimated value is the improvement ratio of energy consumption
efficiency per unit calculated as weighted average, if all units aresupposed to achieve the current target standard, on condition thatthe energy consumption efficiency, the number of units shipped, andthe product constitution of each category in the base year (FY1999)
remain unchanged.
Note 2) The achievement value is the improvement ratio of theweight-averaged energy consumption efficiency in the target fiscal
year (FY2006 or FY2007) to the weight-averaged energy consumption
efficiency in the base fiscal year (FY1999).

2

2. Target scope [See Attachment 1.]
The same for the current standards, transformers to be covered shall be those
whose rated primary voltage is above 600 V and 7,000 V or below and which areconnected to alternating current circuit.
Also the same for the current standards, the following transformers are
excluded from the application of specified equipment.
1)
2)

Those using gas as insulation material (Gas-immersed transformers)
Those using H class insulation material (H class insulation dry-typetransformers)3) Scott-connected transformers
4) Those with 3 or more windings (Multi-winding transformers)5) Pole transformers
6) Those which are single-phase transformers and whose rated capacity is 5
kVA or below, or above 500 kVA7) Those which are three-phase transformers and whose rated capacity is 10
kVA or below, or above 2,000 kVA8) Those which are three-phase transformers using insulation material madeof resin and used to transform three phase alternating current into single
phase alternating current and three phase alternating current (Double
power encapsulated-winding transformers)9) Those whose rated secondary voltage is below 100 V or above 600 V
10) Those which are air-cooled type or water-cooled type

3. Matters to be evaluation standards for manufacturers, etc.
(1) Target fiscal year [See Attachment 2.]
The target fiscal year for transformers shall be FY2014 for bothoil-immersed transformers and encapsulated-winding transformers.
(2) Categories and target standard values for setting targets [See Attachment 3
to 4.]As regards transformers shipped by manufacturers, etc. of transformers
in Japan in the target fiscal year, the value obtained from weight-averaging
energy consumption efficiency measured using the method described inparagraph (3) with the number of units shipped by each manufacturer foreach category in the table below shall not exceed the target standard values.

3[Target standard values for energy consumption efficiency]
Category
Category

Type

NumberRatedof phases frequency

Rated
capacity

Target standard value
calculation formula ofstandard energy
consumption efficiency

50 Hz

500 kVA or
below

E = 11.2･(kVA)0.732

60 Hz

500 kVA or
below

E = 11.1･(kVA)0.725

50 Hz

500 kVA or
below

E = 16.6･(kVA)0.696

50 Hz

Above
500 kVA

E = 11.1･(kVA)0.809

60 Hz

500 kVA or
below

E = 17.3･(kVA)0.678

IV-2

60 Hz

Above
500 kVA

E = 11.7･(kVA)0.790

V

50 Hz

500 kVA or
below

E = 16.9･(kVA)0.674

60 Hz

500 kVA or
below

E = 15.2･(kVA)0.691

50 Hz

500 kVA or
below

E = 23.9･(kVA)0.659

50 Hz

Above
500 kVAE = 22.7･(kVA)0.718

60 Hz

500 kVA or
below

E = 22.3･(kVA)0.674

60 Hz

Above
500 kVA

E = 19.4･(kVA)0.737

I

Single
phase

II
III-1
III-2

Oil-immersed
transformers
Three
phase

IV-1

Single
phase

VI
VII-1
VII-2
VIII-1
VIII-2

Encapsulatedwindingtransformers

Three
phase

Remarks E: Standard energy consumption efficiency of transformers (unit: W)* The reference load factor is 40% for transformers with capacity of 500
kVA or below and 50% for transformers with capacity of above 500
kVA.
kVA: Rated capacity of transformers (unit: kVA)
(Note) In case of semi-standard products, the target standard value calculation
formula for standard energy consumption efficiency of each category shall be
multiplied by the following value.
Oil-immersed transformers: 1.10
Encapsulated-winding transformers: 1.05

4

(3) Method for measuring energy consumption efficiency [See Attachment 5.]
Energy consumption efficiency of transformers in II. (2) shall be “total loss
(W)” and calculated by the following formula; the no load loss (W) and theload loss (W) shall be measured using the method prescribed by JIS C 4304
and JIS C 4306.

Total loss (W) = No load loss (W) +× Load loss (W)Where, the following values shall be used for m.
m: Reference load factor
Transformers whose capacity is 500 kVA or below 40 (%)
Transformers whose capacity is above 500 kVA
50 (%)(4) Display items, etc.
1) Display items
Following items shown from i) to x) shall be specified as display items
regarding energy consumption efficiency of transformers, the same as
those for the current standards.
i)
ii)

Product name and model nameTypeoftransformer(structure)(oil-immersed
encapsulated-winding)iii) Rated capacity (kVA)iv) Number of phasesv) Rated frequency (Hz)vi) Rated primary voltage and rated secondary voltage (V)vii) Energy consumption efficiency (total loss (W))viii) Reference load factor (%)ix) Standard name (standard (JIS standard or JEM standard) or
semi-standard)x) Name of manufacturer, etc.

5or2) Compliance items
Followings shall be compliance items regarding energy consumption
efficiency of transformers, the same as those for the current standards.
- Energy consumption efficiency (total loss W) said in item vii) of
paragraph 1) above shall be indicated to 3 or more significant figures(however, 2 or more significant figures if the efficiency is below 100 W).
- Reference load factor (%) said in item viii) of paragraph 1) above shall be
the value prescribed in the foregoing paragraph (3) in integers.
- Display items listed in paragraph 1) above shall be indicated in an
indelible way on noticeable spots in catalogues describing theperformance of transformers and in materials presented bymanufacturers, etc. when consumers selecting products.
4. Proposals, etc. for energy conservation(1) Actions of Government
From the viewpoint of promoting the spread of transformers withexcellent energy consumption efficiency, the government shall make efforts
to take necessary actions such as the spread and enlightenment activities, inorder to promote actions of users and manufacturers, etc.
(2) Actions of manufacturers, etc.
1) Efforts shall be made to promote technological development for further
energy efficiency of transformers and to develop products with excellent
energy consumption efficiency.
2) From the viewpoint of promoting the spread of transformers withexcellent energy consumption efficiency, efforts shall be made to provide
appropriate information so that users can select transformers withexcellent energy consumption efficiency, by means of, for example,
indicating energy consumption efficiency not only on catalogues and user
manuals but also on easily noticeable spots in materials which
manufacturers, etc. will present to help users select transformers.
(3) Actions of users
Efforts shall be made not only to select transformers with excellent energy
consumption efficiency and adequate capacity, but also to promote energy
conservation by using transformers correctly and efficiently.

6

Attachment 1
Scope of Power Transformers Covered
1. Basic ideas
Transformers covered in this study shall be those whose rated primaryvoltage is above 600 V and 7,000 V or below and which are used in alternating
current circuit. Applicable scope shall include not only transformers withstandard specifications whose capacity, voltage, etc. are prescribed by JIS, etc.
but also transformers with non-standard specifications (semi-standard
products).
2. Transformers excluded out of the scope(1) Those using gas as insulation material (Gas-immersed transformers)
Transformers using sulfur hexafluoride which is one of greenhouse gases
as the base material of insulation. Production of these transformers has
been curtailed because emission of the gas must be contained. (The numberof units shipped in FY2009 is 0.)(2) Those using H class insulation material (H class insulation dry-typetransformers)
Dry-type transformers which use heat resistant class H (tolerable
maximum temperature 180°C) prescribed by JIS C4003 “Thermal
evaluation and classification of electrical insulation” as main insulationbase material and whose surfaces are varnished. They had been used as
emergency transformers before encapsulated-winding transformers wereintroduced.
Shipment of these transformers decreased as
encapsulated-winding transformers spread because their withstand voltage
is lower than that of oil-immersed types as well as because they require
more frequent maintenance than encapsulated-winding types for their poor
dust proof and humidity resistance performance. (The number of units
shipped in FY2009 is 0.)(3) Scott-connected transformers
Transformers which transform three phase alternating current into twophase and can take single phase load from each of them. When a single
phase alternating current load is taken from a three phase alternating
current, unbalanced voltage which affects the primary side is generated;
therefore, Scott-connected transformers are used to minimize this impact.
Because of the volumetric efficiency, they are mainly used for small-scale
facilities such as emergency power supply systems in buildings and factories,
etc. in addition to the usage for electric railway signals. However, thedemand for this type of transformers is not much, compared to the shipmentof transformers as a whole. (The number of units shipped in FY2009 is 388.)7

(4) Those with 3 or more windings (Multi-winding transformers)
Transformers whose winding capacity is designated for each product andwhich are used for special usage such as where one unit supplies two or moretypes of voltage to the secondary side. As a standard product is equipped with
two windings, the voltage supplied to the secondary side is limited to one typeonly, but, in some cases, a product is equipped with multiple windings such as
three or four if multiple voltage supplies are required in factories, etc. The
demand for this type is not much in the shipment of transformers as a whole.
(The number of units shipped in FY2009 is 84.)
(5) Those which are single-phase transformers and whose rated capacity is 5 kVAor below, or above 500 kVA
Small capacity products are frequently used for the usage other thandistribution of electricity, such as usage for the control of breakers, protection
relays, maintenance lights, etc. or for railway signals. As for large capacity
products, the demand is low due to constraints to the capacity and voltage
fluctuation affecting power supply of large current breakers used together, etc.
(The number of units shipped in FY2009 is 119 in case of capacity 5 kVA or
below and 16 in case of capacity above 500 kVA.)(6) Those which are three-phase transformers and whose rated capacity is 10 kVAor below or above 2,000 kVA
Small capacity products are used as power supplies for motors, etc. whose
load is minimal. As for large capacity products, the main application is as
power supplies of places where electric power loads are concentrated such aslarge-scale plants; however, there is no general versatility with these products
for constraints to large current breakers, etc., so the demand for this type oftransformers is not much. (The number of units shipped in FY2009 is 83 in caseof capacity 10 kVA or below, and 149 in case of capacity above 2,000 kVA.)(7) Those which are three-phase transformers using resin insulation material andused to transform three phase alternating current into single phase alternating
current
and
three
phase
alternating
current(Doublepower
encapsulated-winding transformers)
For the use with small cubicle-type power receiving and distributing facilities
for both lighting and powering, oil-immersed transformers are mainly used.
Thus, from the aspect of price, the demand for encapsulated-windingtransformers is not much. (The number of units shipped in FY2009 is 44.)
(8) Those whose rated secondary voltage is below 100 V or above 600 V
Transformers used as power supplies for equipment such as imported
products designed to operate on a rated voltage which is different from the one
generally used in Japan. The demand for this type of transformers is notmuch in the shipment of transformers as a whole. (The number of units shipped
in FY2009 is 212.)8

(9) Air-cooled type transformers and water-cooled type transformers
Most of air-cooled transformers are large capacity models used for power
stations and substations as well as for special high voltage power receiving anddistributing, etc., and the demand for this type of transformers whose capacity
is below 2,000 kVA is not much. (The number of units shipped in FY2009 is 1.)
Water-cooled type transformers are mainly used for electric furnaces, but thedemand for this type of transformers for the purpose of high voltage powerreceiving and distributing is not much. (The number of units shipped in
FY2009 is 0.)9Attachment 2

Target Fiscal Year, etc. of Power Transformers

1. Target fiscal year
Major improvement of energy consumption efficiency of transformers is
mainly made when the efficiency standards of laws, standards, specifications,etc. are changed following the improvement of energy saving technologies ormaterials. Since the model change of transformers is made at the interval of 7
to 8 years, it is thought necessary to give opportunities for transformers to
improve energy consumption efficiency at least once or twice in order to realize
a drastic improvement in the energy consumption efficiency.
In light of the above, it is appropriate to set the target fiscal year oftransformers as FY2014 which is 8 years after FY2006, the target fiscal year of
the current standards for oil-immersed transformers.
Meanwhile, although the target fiscal year for the current standards forencapsulated-winding transformers has been set differently from that foroil-immersed transformers, it is appropriate to set the next target fiscal year as
FY2014, the same as for the oil-immersed transformers, for early energy
efficiency improvement.

2. Improvement achieved in target fiscal year
The improvement ratio of energy consumption efficiency (total loss (W)) in
the target fiscal year is estimated as 12.5% against the current target standard
value on the premise of that the number of units shipped and the productconstitution of each category in FY2009 remain unchanged.
<Summary of estimation>(1) Energy consumption efficiency per unit (total loss (W)) derived fromweight-averaging the target standard values for the transformers shipped
in FY2009 with the number of units shipped.
Approximately 596.1 W/unit

10(2) Energy consumption efficiency per unit (total loss (W)) derived fromweight-averaging the target standard values for the transformers assumed
to be shipped in the target fiscal year with the number of units shipped.
Approximately 521.8 W/unit* As a prerequisite, the number of units to be shipped and the productconstitution are the same as in FY2009.
(3) Improvement ratio of energy consumption efficiency
596.1 W/unit − 521.8 W/unit= Approximately 12.5%
596.1 W/unit

11

Attachment 3

Categories for Setting Targets for Power Transformers
1. Basic ideas
Transformers shall be classified based on the principles referred to as “thebasic idea concerning the development and revision of evaluation standards for
manufacturers, etc. to be considered in relation to the improvement in
performance of specific equipment” (the 10th Energy Efficiency Standards
Subcommittee of the Advisory Committee for Natural Resources and Energy,
revised on June 18, 2007) (hereinafter referred to as “the principles”).
“The basic idea concerning the development and revision of evaluation standards
for manufacturers, etc. to be considered in relation to the improvement in
performance of specific equipment” - Extract Principle 2: Specific equipment is classified based on certain indices. The indices(basic indices) are those which are deeply related to energy
consumption efficiency such as physical amount and functions, andthey are determined considering factors which consumers use as
standards when choosing products (factors representing consumers’
needs).
Principle 3: Target standard value is determined by one value or functional
formula for each category based on the basic indices, where it isfeasible and appropriate to target at the same energy consumption
efficiency.
Principle 4: When setting categories, additional functions are disregarded inprinciple. However, if the energy consumption efficiency of a productwithout a certain additional function is set as a target standard value,other products with additional functions may withdraw from themarket, despite that market needs for the latter products are thought
to be high, because they cannot comply with the target standard value.
If the probability of such case is high, then it is acceptable to makeanother category (sheet) for those products.
Principle 5: As regards products which are expensive but excellent in energy
consumption efficiency because they use advanced energy saving
technologies, although it is possible to classify them into separate
categories, it is desirable to treat them in the same category withothers wherever possible so that manufacturers can actively sell the
products with excellent energy consumption efficiency.
Principle 6: When setting a target standard value for a category, special products
shall be excluded. However, availability of technologies employed insuch special products shall be also reviewed when studying the future
efficiency improvement possibly realized by technology development,
etc.

12

2. Specific classification method
Characteristics of transformers vary according to specifications such as
structure, the number of phases, rated frequency and capacity, etc., and load factor,
and these factors affect the energy consumption efficiency (total loss) oftransformers. Thus, they are basically classified as follows.
(1) Classification based on basic functions
1) Classification by structure
Oil-immersed transformers and encapsulated-winding transformers differ
greatly each other in their insulation and cooling systems. The former uses
insulating oil and its cores and windings are immersed in a container andcooled by circulation of the insulating oil. The latter uses resin layers andair; the windings are covered with resin layers, whose surfaces are cooled byair.
Therefore, oil-immersed transformers and encapsulated-windingtransformers are classified differently, because they are different in materials
used and structures.
2) Classification by the number of phases
Regarding winding and core configurations, a three-phase transformer uses
three low-voltage windings, three high-voltage windings, and a three-phase
three-leg type core, while a single-phase transformer uses two low-voltage
windings, two high-voltage windings, and a single-phase two-leg type core.
Because of differences in characteristics due to these configurations,transformers are classified into single phase types and three phase types.
3) Classification by rated frequency
According to power supply frequency, material characteristics of magnetic
steel sheet and amount of material used for transformer cores vary (a 50 Hz
transformer usually has a core whose sectional area is 1.2 times larger thanthat of a 60 Hz transformer, because the core’s magnetic flux density isinversely proportional to the frequency), resulting in variation in transformer
characteristics. Therefore, transformers are classified by power supply
frequency, 50 Hz or 60Hz.
4) Classification by capacity
Transformers are classified into a type with a capacity of 500 kVA or below
and a type with a capacity above 500 kVA because annual mean equivalentload factor differ between special high demand users and high voltage users
and because JIS-compliant transformers (500 kVA or below) are used for JIS
cubicle-type high voltage power receiving and distributing facilities.
However, a category with a capacity above 500 kVA is not provided forsingle-phase transformers because they are the products excluded from theapplicable scope.

13

(2) Classification by voltage, connection, or other specifications
Semi-standard products whose voltage and connection are different from the
JIS standard are generally made based on standard products but by means ofmodifying the optimized design of standard products, so the characteristics ofsemi-standard transformers are inferior to those of standard transformers.
Besides, reducing the loss of semi-standard products to the level of standard
products will result in increased costs due to increases in the number of wiretypes as well as in the number of jigs for production of cores and windings.
Meanwhile, to simplify the classification, semi-standard transformers areclassified into the same category as standard transformers along with certain
corrections, instead of making an additional category to standard transformers.
Classifications of standard and semi-standard products are shown in Table 3-1
below.

Table 3-1 Standard and semi-standard productsStandard
product

Specifications

Primary voltage (V)500 kVA
or belowSingle phase 210 to 105 V,
Three phase 210 V
6.6 kVAbove
500 kVA

Semi-standard
product

Secondary voltage (V)6.6 kV,
6.6/3.3 kV,
3.3 kV

Three phase 210 V
Three phase 50 Hz 420 V,
Three phase 60 Hz 440 V
100 V or above and 600 V
or below, excluding above
voltages

14

Remarks

JIScompliant

(3) Categories for setting targets
Based on the ideas mentioned in (1) and (2) above, categories for setting
target standards are shown in Table 3-2 below.
Table 3-2 Categories of transformers
CategoryType

I

Single
phase

II
III-1
III-2

NumberofphasesOil-immersed
transformers
Three
phase

IV-1
IV-2
V

Single
phase

VI
VII-1
VII-2
VIII-1

Encapsulated-win
ding transformers
Three
phase

VIII-215

Ratedfrequency

Rated capacity

50 Hz

500 kVA or below

60 Hz

500 kVA or below

50 Hz

500 kVA or below

50 Hz

Above 500 kVA

60 Hz

500 kVA or below

60 Hz

Above 500 kVA

50 Hz

500 kVA or below

60 Hz

500 kVA or below

50 Hz

500 kVA or below

50 Hz

Above 500 kVA

60 Hz

500 kVA or below

60 Hz

Above 500 kVA

Attachment 4
Target Standard Values for Power Transformers
1. Basic ideas
Target standard values are set based on the idea of Top Runner method.
Specific ideas are as follows.
1) Target standard values are set for each category classified appropriately.
2) As regards transformers for which improvement of the efficiency can be expected
due to technological development in the future, target standard values are set
taking such improvement into consideration as much as possible.
3) Target standard values shall not be inconsistent between categories.

2. Formula for calculating specific target standard values (standard energy
consumption efficiency)(1) Development of relational expression using actual measurement values(FY 2009)
Since the measurement method is the same as that of the current
standards, an approximation expression is used this time too to show thecorrelation between the capacity and the total loss of transformers, which are
obtained by taking the logarithm of both and making a linear function from it.
This is transformed into an exponential function to primarily show thecorrelation between the capacity and the total loss of transformers.
E = A × (kVA) B
Where,

E: Energy consumption efficiency (total loss (W))
Total loss when the load factor is 40% (500 kVA or below)
Total loss when the load factor is 50% (Above 500 kVA)
kVA: Capacity of transformer (kVA)A, B: Constant of each category(2) Expected improvement of energy consumption efficiency due totechnological development in the future
Technological development of transformers has been pursued to improvethe convenience of users and enhance the energy consumption efficiency. As
regards the improvement of energy consumption efficiency of transformers,
efforts have been made to improve loss by 30% to 40% by means of
performance enhancement of core materials and winding materials as well as
improvement of processing technologies for cores and windings.
Since further technological development can be expected in the future,
which is the improvement in characteristics of magnetic steel sheet as corematerials, it shall be taken into consideration in setting target standard
values of this time.
16

As for magnetic steel sheets as core materials of the current Top Runnertransformers, those with iron loss of 0.90 W/kg are mainly used, which are
the highest quality magnetic steel sheets having general versatility andhigh orientation among ones in the JIS C2553 “Grain-oriented magnetic
steel sheet and strip” shown in Table 4-1 below. To further improve theloss characteristic, it becomes necessary to use highly-efficient magnetic
steel sheet whose iron loss is 0.85 W/kg or below as the standard material,
which shall be developed through the study of core materials. It is also
necessary to improve the processing technology which prevents material's
iron loss characteristic from deteriorating when manufacturing cores.

Table 4-1

Loss characteristics of magnetic steel sheets
Sheet thickness
(mm)

Type
23P90
High
orientation

0.90 or below
0.23

23P95
23P1000.95 or below
1.00 or below

27P1000.27

27P11023R85
Magnetic
domaincontrol

Iron loss (W/kg)

0.23

23R90
27R90

0.27

27R95

1.00 or below
1.10 or below
0.85 or below
0.90 or below
0.90 or below
0.95 or below

Source: Table 1, JIS C2553 “Grain-oriented magnetic steel sheet and strip”

If 0.85 W/kg oriented magnetic steel sheets are used in terms ofapplying the future technology to magnetic steel sheets, the improvement
in no load loss will become 5%.
Accordingly, if it is in the case of total
loss, the efficiency improvement can be expected to be 2.5%, and then it isadded to the calculation (1) above.
Effect of the 5% no load loss improvement in total loss is shown in Table
4-2 below, while taking an oil-immersed transformer with averagecapacity of 150 kVA as an example.

17

Table 4-2 Effect of 5% no load loss improvement in total loss
(Example of oil-immersed transformer with average capacity of 150 kVA)
Characteristic when
Characteristic of JIS
Items
adopting W17/50 − 0.85 W
standard transformercore
No load loss (W)

276

262

Load loss at the time of
40% load (W)

295

295

Total loss (W)

571

557

−

2.5

Improvement ratio (%)

Note: The characteristic of JIS standard transformer is the averagecharacteristic of JIS standard transformers researched by the Japan
Electrical Manufacturers’ Association.

(3) Allowance for special products
Principle 6 of “the basic idea concerning the development and revisionof evaluation standards for manufacturers, etc. to be considered inrelation to the improvement in performance of specific equipment” (the10th Energy Efficiency Standards Subcommittee of the Advisory
Committee for Natural Resources and Energy, revised on June 18, 2007)
stipulates as follows: “When setting a target standard value for acategory, special products shall be excluded. However, availability oftechnologies employed in such special products shall be also reviewed
when studying the future efficiency improvement possibly realized bytechnology development, etc.” Therefore, when setting target standard
values for oil-immersed transformers and encapsulated-windingtransformers, the improvement ratio of 1.3% shown in Table 4-3 below
shall be added to the calculation (1) above to allow for the low loss
technology of ultra-high efficiency transformers (those using amorphousalloy or those having domain-refined magnetic steel sheet redesigned foreven lower magnetic field).

18

Table 4-3

Loss improvement ratio of JIS standard productsType

Oil-immersed
transformers

Encapsulated-windingtransformers

1) Total number of units shipped
43,628
5,084(units/year)
2) Number of ultra-high efficiency
624
350
transformers shipped (units/year)3) Ratio of special transformers (2)/1))
1.4
6.9
(%)
4) Total loss if all of the units shipped isstandard products with minimum
22,025
5,150
loss (kW)5) Loss improvement of ultra-high238
111
efficiency products (kW)6) Improvement ratio realized by
1.1
2.2
ultra-high efficiency transformers(%) (*1) (*2)
Source: Research conducted by Japan Electrical Manufacturers’ Association(* The number of units shipped is the actual shipment of FY2009.)

Total
48,712974
2.0
27,175349
1.3(*1) The improvement ratio realized by ultra-high efficiency transformers is thevalue in the case that all of the units shipped, as for each of oil-immersed
transformers and encapsulated-winding transformers, are JIS standard
products.
(*2) The ratio of ultra-high efficiency transformers shipped is 2.0% and theweight-averaged improvement ratio is calculated as approximately 1.3%,
making the average improvement ratio approximately 165%/unit.

(4) Total loss correction factors for semi-standard products
Regarding transformers operating on different voltage from standard
products and having mixed corrosion guard plate, the total loss increase
when comparing to standard products shall be taken as a correction
multiplying factor. Products that specifically use an impedance voltage
other than the level recommended by the manufacturer are included in thesemi-standard products for the purpose to enhance further energy efficiencyof them.
Total loss correction factors for semi-standard products shall be the sameas those used in the current evaluation standards for the reason that there is
no structural change, and are shown in Table 4-4 below.
Table 4-4

Total loss correction factors for semi-standard products
as compared to standard voltage products
Type
Total loss correction factors (%)

Oil-immersed transformers
Encapsulated-windingtransformers

10
5
19

(5) Basic ideas concerning target standard values
Based on the categories of transformers, the Top Runner values are
obtained from the actual measurement values (based on actual shipmentof FY2009) of total loss, which is energy consumption efficiency, and thentarget standard values are studied.
To set target standard values, the following procedures are followed.
(See Figure 4-1.)
1) Take a Top Runner value of each capacity and then calculate an
approximate line (approximation expression A).
2) While keeping the inclination, translate the approximation expression
A to the Top Runner value so that none of the other Top Runner values
are below the approximation expression (approximation expression B).
3) Apply expected efficiency improvement discussed in paragraph (2) and(3) above to the approximation expression B, which is an efficiency
improvement to be realized by future technologies and an efficiency
improvement caused by special products. Then, develop a calculation
formula for a target standard value (target standard value calculation
formula).

Energy consumption Efficiency

Poor

悪
い

エ
ネ
ル
ギ

○
○
○

Approximation
近似式ＢB
expression○○○

Target standard
目標基準値
value
calculation
算定式
formula○○Excellent○良いApproximation
近似式ＡA
expression

○

○

ー

消
費
効
率

○

Efficiency improvement
現行の技術によexpected from current
technologies
る効率改善分Efficiency
improvement
将来技術による
expected from futuretechnologies
効率改善分
consumption efficiency of○ ：Energy
現行製品のエネルギー消費効率
current
products
現行のトップランナー製品のconsumption efficiency of○ ：Energy
current Top Runner products

エネルギー消費効率

capacity (kVA)
定Rated
格容量（kVA）

Figure 4-1 Image of development of target standard value calculation formula20

(6) Target standard value calculation formulae
Target standard value calculation formulae which consider the factors
stated in (1) to (5) above are shown in Table 4-5 and Table 4-6 below.

Table 4-5 Improvement ratio of standard energy consumption efficiency andtarget standard value calculation formula for each category of transformers
Category
区分
Type of
変圧器のtransformer
種別

Numberof
相数phasesSingle単相
phase

Oil-immers
油入
ed
変圧器
transformer

Rated
定格
frequency
周波数

Rated
capacity
定格容量

Efficiency
現行技術に
improvement
by current
よる効率改technologies

善分

Efficiency

Efficiency

将来技術にimprovement 特殊品の技
improvement by
by futuretechnologies of
術による効
よる効率改
technologies
special products
率改善分
善分

Ｂ

11.6

0.732

9.7%

2.5%

1.3%

11.5

0.725

9.0%

2.5%

17.3

0.696

8.5%

50 0kVA超過
500 kVA

11.5

0.809

500 kVA or
5 00kVA以下
below

18.0

Above
50500
0kVA超過kVA

50Hz

500 kVA or
5 00kVA以下
below

60Hz

5 00kVA以下
below

0.732

12.8%

1.3%

3.8%

11.1

0.725

12.2%

2.5%

1.3%

3.8%

16.6

0.696

11.7%

6.6%

2.5%

1.3%

3.8%

11.1

0.809

9.9%

0.678

8.0%

2.5%

1.3%

3.8%

17.3

0.678

11.6%

12.2

0.790

10.5%

2.5%

1.3%

3.8%

11.7

0.790

14.2%

17.6

0.674

10.6%

2.5%

1.3%

3.8%

16.9

0.674

14.2%

15.8

0.691

12.0%

2.5%

1.3%

3.8%

15.2

0.691

15.4%

5 00kVA以下
below

24.8

0.659

10.6%

2.5%

1.3%

3.8%

23.9

0.659

13.9%

Above
50500
0kVA超過
kVA

23.6

0.718

7.4%

2.5%

1.3%

3.8%

22.7

0.718

11.0%

500 kVA or
5 00kVA以下
below

23.2

0.674

12.1%

2.5%

1.3%

3.8%

22.3

0.674

15.5%

Above
50 0kVA超過
500 kVA

20.2

0.737

10.1%

2.5%

1.3%

3.8%

19.4

0.737

13.2%

500 kVA or
500 kVA or

5 00kVA以下
below
Above

500 kVA or
500 kVA or

Three
phase
三相

60Hz

Improvement

current
行基準値
現from
standard value
からの改善

11.2

5 00kVA以下
below

50Hz

算定式

3.8%

60Hz

60Hz

計

Targetstandard value
目標基準値
calculation formula

Ｂ

50Hz

Three

Total

Ａ

500 kVA or
500kVA以下
below

50Hz

Singlephase
単相Approximation
近似式ＢB
expression

Ａ

三相
phase

Encapsulat
モールド
ed-winding
変圧器
transformer

Target standard
value calculation
formula (E = A･(kVA)^B)
目標基準値算定式（ Ｅ=Ａ・（ｋＶＡ）＾Ｂ）

21

Table 4-6
Category

Standard energy consumption efficiency of transformers

Type

Classification
NumberRatedoffrequency
phasesI

Single
phase

II
III-1
III-2

transformer

IV-1

Three
phase

60 Hz

50 Hz
60 Hz
60 Hz

IV-2
V

Single
phase

VI
VII-1

500 kVA or
below
500 kVA or
below
500 kVA or
below
Above
500 kVA
500 kVA or
below
Above
500 kVA
500 kVA or
below
500 kVA or
below
500 kVA or
below
Above
500 kVA
500 kVA or
below
Above
500 kVA

50 Hz

50 Hz

Oil-immersed

Encapsulated-

50 Hz
60 Hz
50 Hz

winding
VII-2
VIII-1
VIII-2transformer

Three
phase

Rated
capacity

50 Hz
60 Hz
60 Hz

Target standard value
calculation formula ofstandard energy consumption
efficiency
E = 11.2･(kVA)0.732
E = 11.1･(kVA)0.725
E = 16.6･(kVA)0.696
E = 11.1･(kVA)0.809
E = 17.3･(kVA)0.678
E = 11.7･(kVA)0.790
E = 16.9･(kVA)0.674
E = 15.2･(kVA)0.691
E = 23.9･(kVA)0.659
E = 22.7･(kVA)0.718
E = 22.3･(kVA)0.674
E = 19.4･(kVA)0.737

Remarks E: Standard energy consumption efficiency of transformer (unit: W)* The reference load factor is 40% for transformers with capacity of
500kVA or below and 50% for transformers with capacity of above
500kVA.
kVA: Rated capacity of transformer (unit: kVA)
(Note) In case of semi-standard products, the target standard value calculation
formula of the standard energy consumption efficiency of each category shallbe multiplied by the following value.
Oil-immersed transformers: 1.10
Encapsulated-winding transformers: 1.05

22

(Reference)

Total loss (W) at load factor of 40%

1. Correlation between capacity and energy consumption efficiency (totalloss) of transformers(1) Oil-immersed transformers (Category I to IV-2)

Total loss (W) at load factor of 40%

Capacity (kVA)
Category I Oil-immersed transformer, Single phase, 50 Hz, 500 kVA or below

Capacity (kVA)
Category II Oil-immersed transformer, Single phase, 60 Hz, 500 kVA or below

23

Total 負荷率40%時の損失(W)loss (W) at load factor of 40%

10,000

1,000
0.696

y = 16.6x

100

10
10

100
1000
Capacity(kVA)
容量(ｋVA)
Category III-1 Oil-immersed
phase, 50 Hz, 500 kVA or below
区分Ⅲ-1 transformer,
油入変圧器 Three
三相・50Hz・500kVA以下

負荷率50%時の全損失(W)Totalloss (W) at load factor of 50%

10,0000.809

y = 11.1x

1,000
100

1000

10000

Capacity(kVA)
容量(ｋVA)
Category III-2 区分Ⅲ-2
Oil-immersed
transformer,三相・50Hz・500kVA超過
Three phase, 50Hz, above 500 kVA
油入変圧器

24

Total loss (W) at load factor of 40%

Capacity (kVA)
Category IV-1 Oil-immersed transformer, Three phase, 60 Hz, 500 kVA or below

Total負荷率50%時の全損失(W)loss (W) at load factor of 50%

10,0000.790

y = 11.7 x

1,000
100

1000
10000
Capacity(kVA)
容量(ｋVA)
Category IV-2 Oil-immersed
transformer, 三相・60Hz・500kVA超過
Three phase, 60 Hz, above 500 kVA
区分Ⅳ-2 油入変圧器

25(2) Encapsulated-winding transformers (category V to VIII-2)

Totalloss (W) at load factor of 40%
負荷率40%時の全損失(W)10,000

1,000
0.674

y = 16.9x

100

10
10

100

1000

Capacity(kVA) )
容量(ｋVA
Category V Encapsulated-winding transformer, Single phase, 50 Hz, 500 kVA or below

区分Ⅴ モールド変圧器 単相・50Hz・500kVA以下

Total負荷率40%時の損失(W)loss (W) at load factor of 40%

10,0001,000
y = 15.2x0.691

100

10
10

100
Capacity(kVA)
容量(ｋVA)
Category
VI 受配電用変圧器（モールド変圧器・60Hz・500kVA以下）
Encapsulated-winding transformer, 60 Hz, 500 kVA or below
区分Ⅵ

26

1000

Total負荷率40%時の全損失(W)loss (W) at load factor of 40%

10,000

1,000
0.659

y = 23.9x

100
10

100
1000
CapacityｋVA)
容量((kVA)
Category VII-1 Encapsulated-windingtransformer, Threephase, 50 Hz, 500 kVA or below
区分Ⅶ-1 モールド変圧器
三相・50Hz・500kVA以下

Total 負荷率50%時の全損失(W)loss (W) at load factor of 50%

10,0000.718

y = 22.7x

1,000
100

1000

Capacity(kVA) A)
容量(ｋV
Category VII-2 Encapsulated-windingtransformer,
phase, 50 Hz, above 500 kVA
区分Ⅶ-2 モールド変圧器Three
三相・50Hz・500kVA超過

27

10000

Total負荷率40%時の全損失(W)loss (W) at load factor of 40%

10,000

1,000
0.674

y = 22.3x

100
10

100

1000

CapacityｋVA)
容量((kVA)
Category VIII-1 Encapsulated-windingtransformer,
phase, 60 Hz, 500 kVA or below
区分Ⅷ-1 モールド変圧器 Three
三相・60Hz・500kVA以下

Total負荷率50%時の損失(W)loss (W) at load factor of 50%

10,0000.737

y = 19.4x

1,000
100

1000
10000
Capacity(kVA)
容量(ｋVA)
Category区分Ⅷ-2
VIII-2 Encapsulated-windingtransformer, 60 Hz, above 500 kVA
受配電用変圧器（モールド変圧器・60Hz・500kVA超過）

28

Attachment 5
Energy Consumption Efficiency of Power Transformers
and its Measurement Method
1. Basic ideas
Transformers have been designated as specified equipment since FY2002,
and total loss (W) prescribed in JIS C4304 “6kV Oil-immersed distribution
transformers” and JIS C4306 “6kV Encapsulated-winding distribution
transformers” has been adopted to be used for the evaluation of energy
consumption efficiency and its measurement method.
When studying new standards, it is deemed reasonable to continue to use it
as a practical index to evaluate energy consumption efficiency of transformers.
2. Specific energy consumption efficiency and its measurement method(1) Energy consumption efficiency
Energy consumption efficiency of transformers shall be the total loss (W)based on the no load loss 1 the load loss 2 and the load factor, which is calculatedby the following formula.
Total loss (W) = No load loss (W) +× Load loss (W)Where, the following values are used for m.
m: Reference load factor (See attachment. )Transformers whose capacity is 500 kVA or below 40 (%)
Transformers whose capacity is above 500 kVA
50 (%)
Loss (W) is being used as energy consumption efficiency of transformers
under the current standards for the reason described in the following
paragraph.
In addition, no particular changes are observed in thecircumstances. Therefore, the loss continues to be used to indicate energy
consumption efficiency of transformers.
If efficiency 3 is used to indicate energy consumption efficiency of
1 No load loss: Loss made of eddy current loss, hysteresis loss, etc. that are generated in the coreby alternating flux.

2 Load loss: Loss generated by resistance in the winding part, specifically by load current of thesecondary side.

3 Efficiency: {Effective output (Capacity × m) / (Effective output (Capacity × m) + Loss at m)}29

transformers, the loss will become extremely small against the effective output
and the energy saving turns out to be a value under the decimal point. In thiscase, when calculating the amount of energy to be saved, it needs to beconverted to loss, making its handling inconvenient. Therefore, loss is used toindicate energy consumption efficiency because being an absolute value makes
it easy to handle and because it can be expressed by the unit of W (watt)allowing easier application to other purposes such as calculation of effect, etc.
By the way, loss used here as energy consumption efficiency is the loss
generated when a transformer operating at prescribed load factor.

(2) Measuring method of energy consumption efficiency
Measuring method of no load loss and load loss shall be in accordance with
“9.2 Measurement of Winding Resistance”, “9.3 No load Current and No Load
Loss Testing”, and “9.5 Load Loss and Short-circuit Impedance Testing”
stipulated by JIS C 4304 “6kV Oil-immersed distribution transformers” andJIS C 4306 “6kV Encapsulated-winding distribution transformers”.

30Attachment
Reference Load Factor
When setting a reference load factor, considering the fact that load loss
greatly changes (3 to 8 times greater than the case of no-load loss) depending on
a reference load factor used, it is necessary to pay attention to that 1) it is avalue based on actual use and 2) sufficient energy saving effect can be achieved
even if the load factor actually used changes. From these points of view, study
is made to set reasonable reference load factor.
1. Type of rated capacity based on JIS
The scope of JIS C 4620 “Cubicle type high voltage power receiving units”
which is a standard for high voltage power receiving and distributing unit
covers transformers whose capacity per unit is 500 kVA or below.
This is because this type of transformers accounts for the most part of thewhole transformers shipped, as exemplified by the fact that even atransformation unit (cubicle) installed by a high voltage user having powerreceiving capacity of 4,000 kVA or below consists of transformers whose
capacity is 500 kVA or below.
Meanwhile, transformers whose capacity is above 500 kVA are mainly used
for power supply of medium and large scale factories of special high voltage
users.
Thus, the usage of transformers can be divided at the boundary of 500 kVA.
External Specifications

Internal Specifications

Three phasetransformer

Single phasetransformer

A cubicle type high voltage power receiving unit is a distribution board incorporating transformers,
switches, measurement instruments, protection devices. Among them, there are two transformers, i.e.
a three phase transformer for power load and a single phase transformer for load from lights andoutlets. It is mainly used for the power supply system of small scale factories, stores, public facilities(schools, community halls), small-scale buildings, etc.

31

2. Selection of reference load factor(1) Research results of reference load factor
According to the survey of user companies on annual load factor conducted by
the Japan Electrical Manufacturers’ Association and Japan Switchboard andControl System Industries Association in FY2010, the annual load factor is
36.4% in daytime, 9.7% at nighttime and 26.6% in average for transformers of
500 kVA or below, and the annual load factor is 47.1% in daytime, 29.6% atnighttime and 39.3% in average for transformers of above 500 kVA.
However, this result needs to consider the correction of power factor made bya phase advanced capacitor.
In power receiving units, the load power factor on the secondary side of atransformer is normally from 0.80 to 0.85 and the actual load factor of atransformer is higher than that of the high voltage receiving end. Generally, aphase advanced capacitor is used on high-voltage receiving ends with the aim ofachieving a power factor of 0.95, and thus the actual load factor of transformers
is higher by 12% to 19%.
Based on this, the actual load factor is estimated to be approximately 11% to
42% for transformers of 500 kVA or below and approximately 34% to 54% fortransformers of above 500 kVA.
(2) Adequacy of reference load factor
According to the research said in the foregoing paragraph (1), the average loadfactor by user’s application shifted as shown in Table 1 below.
Table 1Comparison of average load factor by user’s application
FY2001FY2010

Factories

40.8%

31.4%

Buildings

19.7%

29.4%

Public facilities

21.0%

40.8%

Load factor by user’s application varies greatly and there is no consistency inthe change of load factor.
In other words, when determining a certain reference load factor, whileconsidering the actual load factor, it is necessary to pay attention to the energy
saving effect regardless of how it is used (changes of the load factor).
Figure 1 shows the values of total loss of a normal three-phase 200 kVAtransformer (current average) whose efficiency was already improved by 20%,
when it is designed to achieve the highest efficiency at the reference load factorof 20%, 30%, 40% 50% and 60% respectively. Figure 2 shows these values inindex numbers while taking the current average as 1. As Figure 2 shows, theefficiency of the transformer improved in a way that achieves the highest
efficiency at the reference load factor of 40% is better than that of the current
product in the whole area, indicating that an effective energy saving standard
can be set by selecting an intermediate value of the reference load factors. If
an extreme load factor is used, to the contrary, it may deviate from practical use
32

Energyconsumption efficiency (W)エネルギー消費効率（Ｗ）

and give disadvantage to users.

2000
現行平均値
基準負荷率20%
Referenceload factor 30%
基準負荷率30%
Referenceload factor 40%
基準負荷率40%
Referenceload factor 50%
基準負荷率50%
Referenceload factor 60%
基準負荷率60%

1500

Current average value

Reference load factor 20%

1000
500
0
20%

30%

40%
Load factor(%)
負荷率（％）

50%

60%

Energyconsumption efficiency ratio (pu)
ｴﾈﾙｷﾞｰ消費効率比（ｐｕ）

Figure 1 Load factor and total loss characteristic by optimal load factor

1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0

現行平均値
基準負荷率20%
Referenceload factor 30%
基準負荷率30%
Referenceload factor 40%
基準負荷率40%
Referenceload factor 50%
基準負荷率50%
Referenceload factor 60%
基準負荷率60%
Current average value

Reference load factor 20%

20%

30%

40%
Load
factor (%)
負荷率（％）

50%

60%

Figure 2 Load factor and total loss characteristic by optimal load factor
3. Specific reference load factor
Based on the above, in the review of new standards, it is appropriate to set thereference load factor for each capacity as follows likewise in the current
evaluation standards.
500 kVA or below:
Above 500 kVA :

40%
50%

33

Attachment 6

Power Transformer Evaluation Standards Subcommittee
Energy Efficiency Standards Subcommitteeof the Advisory Committee for Natural Resources and Energy
Meeting History

1st Subcommittee (June 29, 2010)- Regarding publication of Power Transformer Evaluation Standards
Subcommittee- Regarding status quo of transformers- Regarding the state of achievement of transformers- Regarding the scope of transformers- Regarding energy consumption efficiency of transformers and its
measurement method- Others
2nd Subcommittee (November 28, 2011)- Regarding the result of research on pole transformers- Regarding categorization of transformers for setting target- Regarding target fiscal year and target standard values for transformers- Regarding interim report- Others

34

Attachment 7
Power Transformer Evaluation Standards Subcommittee
Energy Efficiency Standards Subcommitteeof the Advisory Committee for Natural Resources and Energy
List of Members
Chairman

Ryuichi Yokoyama

Professor, Graduate School of Environment and Energy
Engineering, Faculty of Science and Engineering,
Waseda University

Members

Kenji Ishiwatari

Japan Switchboard & Control System Industries
Association (Manager, Power Distribution Board
Designing Section, Osaki Electric Systems Co., Ltd.)

Tatsuki Okamoto

Chief Researcher, Electric Power Engineering ResearchLaboratory, Central Research Institute of ElectricPower Industry

Akio Tanaka

Manager, Planning and Research Office, Jyukankyo
Research Institute Inc. (Replaced by Mr. Tsurusaki
below from the second meeting)

Keidai Tsurusaki

Chief Researcher, Jyukankyo Research Institute Inc.
(from the second meeting)

Yoichi Hanji

General Manager, Energy Conservation Technology
Division, the Energy Conservation Center, Japan

Yoichi Hori

Professor, Graduate School of Frontier Sciences, The
University of Tokyo

Hiroshi Matsuzaki

Japan Electrical Construction Association (Manager,
Engineering Control Section, Facility Engineering
Department, Yurtec Co., Inc.)

Yoshio Mochizuki

Chief, Transformer and Specified Equipment
Evaluation Standard WG, the Japan Electrical
Manufacturers’ Association (Adviser in charge ofdevelopment and designing of stationary equipment,
Toshiba Corporation)

Koichi Yasuoka

Professor, Graduate School of Science, Tokyo Instituteof Technology

Hiroshi Yoshimiya

Chief Engineer and Senior Expert, Administration
Division, Nikken Sekkei Ltd.

Yuichi Watabe

Institute of Electrical Installation Engineers of Japan(Leader, Facility Design Supervising Group, Kajima
Corporation)(In Japanese alphabetical order)

35

Reference 1
Status Quo of Power Transformers
I. Types and Classification
1. Utilization of transformers
Electricity generated by power stations is transmitted to users throughtransmission lines and distribution lines, where transformers are used as
equipment for efficient electricity sending.
Generated electricity istransmitted after its voltage being raised to an appropriate level by atransformer at a power station, and then utilized after its voltage being
decreased to required levels at a transforming station on the way or at atransformer of user side.
As for transformers used for high voltage distribution, there are transformers
installed by users as their own facility and pole transformers installed byelectric power companies to distribute 200V/100V electricity to general homes.
Transformers to which the Top Runner standard of the Energy Conservation
Law is applied are those installed by users, which are used in buildings,
factories, commercial facilities, etc. to decrease 6 kV distribution voltage (partly
3 kV) down to low voltage of 600 V or below appropriately according to theequipment used.
Power
plant
発電所
Fire
火力

Nuclear
原子力

500 k to 275 kV
500k～275kV

154 k to 66 kV
154k～66kV

Hydro
水力

Primarytransformation station
一次変電所

Ultra
high voltage
超高圧変電所transformation station

Boosting transformer
発電所用昇圧変圧器

154 k to 66 kV
154k～66kV

66 kV
66kV

33k～
33 k to22kV
22kV
33 k to 22 kV
33k～22kVIntermediate
中間変電所
transformation station

6 kV
6kV
Distribution

配電用変電所transformation station
6 kV
6kV

Pole transformer
柱上変圧器
210 to 105 V
210～105V

General home
一般住宅

Special high voltage receiving
transformer

特別高圧受電用変圧器

factory
Large building グ Large
大工場
大ビルディン

Commercial
facility
業務用施設

Building
中小工場 ビルディング

Medium or small
factory

Oil-immersed
Top Runner transformer
油入トップランナー変圧器
Special high voltage
特別高圧変圧器
transformer
66 to 22 kV/6 kV(3 kV)
66～22kV/
6kV(3kV)

Figure I.1

Large
factory
大工場

Runner transformer
トTop
ップランナー変圧器(For in-house secondary（所内二次変電所用）
transformation station)
6 kV(3 kV)/400 V, 210 V,
6kV(3kV)/400V,
210 to 105 V
210V, 210-105V
Load
負荷

Crowdedcity
過密都市
Encapsulated-winding
Top Runner transformer
モールドトップランナー変圧器

Top Runner transformer 器
トップランナー変圧66kV(3kV)/400V,
kV (3 kV)/400 V, 210 V,
210 to 105 V
210V,210-105V

Load
負荷

Schematic of power transmission and distribution system

2. Types and structure of transformers
362.1 Types of transformers
Structure of transformers is classified into those shown in Figure I.2 below.
Of these types, the Top Runner standard is applied to oil-immersed
transformers and encapsulated-winding transformers.
Classifications ofstandards according to relevant standards are shown in Table I.1.

Oil-immersed transformer

油入変圧器(Figure（図Ⅰ.3）
I.3)

Encapsulated-winding

Transformer
変圧器

モールド変圧器
transformer （図Ⅰ.4）(Figure I.4)

Dry-type

乾式変圧器
transformer
H class dry-type

H 種乾式変圧器
transformer
Gas insulation

ガス絶縁変圧器
transformer

Figure I.2

Types of transformers<Overview of transformers by type>Oil-immersed transformers:
Transformers which store their cores and windings in containers filled withinsulation oil. This type accounts for approximately 90% of transformers as awhole.
Encapsulated-winding transformers:
Transformers in which the entire surface of their primary windings andsecondary windings is covered with resin or insulation material containing
resin.
H class dry-type transformers:
Dry-type transformers using heat resistance class H (allowable maximum
temperature 180℃) as base insulation material and whose surface is varnished.
As encapsulated-winding transformers spread, the production of this type forhigh voltage and extra high voltage is decreasing.
Gas insulation transformers:
Transformers which store the cores and windings in containers filled withinert gas. Generally, sulfur hexafluoride (SF6) is used as the inert gas. Thesetransformers are used at places where disaster prevention is specificallyrequested. The production quantity of this type for high voltage is few.

37

Iron core (core)
Tank

Winding (coil)Figure I.3

Structure of oil-immersed transformer

Iron core (core)

Winding (coil)Figure I.4

Structure of encapsulated-winding transformer

38

Table I.1

Classification of transformers according to relevant standards

Number and name ofstandard

Application

JIS C 4304: 6kV
oil-immersed
distribution
transformers
JIS C 4306: 6kV
encapsulated-winding
distribution
transformers

Applied totransformers ofstandard
specifications
compliant withevaluation
standards fortransformers as
specifiedequipment.

JEM 1482: Standard
value for energy
consumption efficiencyof oil-immersed
transformers for highvoltage power receiving
and distributing,designated as specified
equipment
JEM 1483: Standard
value for energy
consumption efficiency
ofencapsulated-windingtransformers for highvoltage power receiving
and distributing,designated as specified
equipment
Power Transformers(JEC2200
Transformers)

Applied totransformers ofsemi-standard
specifications
compliant with JIC
C 4304, JIS C 4306
and JEC-2200.

Applied totransformers otherthan those for JIS C
4304, JIS C 4306,
measuring
instruments,
grounding, arc
extinguishing,
semiconductor
power conversion
systems, starting,testing, vehicles,
welding,communicating aswell as induction
voltage adjustors.

39

Capacity
range

Primary voltage/
secondary voltage

Single phase:
10, 20, 30, 50,
75, 100, 150,
200, 300, 500
kVA
Three phase:
20, 30, 50, 75,
100, 150, 200,
300, 500, 750,
1000, 1500,
2000 kVA
Single phase:
10 kVA to 500
kVA
Three phase:
20 kVA to2000 kVA

Single phase:
6.6 kV/210 to 105 V
Three phase:
6.6 kV/210 V(1000 kVA or below)
6.6 kV/420 V, 440 V(1500, 2000 kVA)

Single phase:
1kVA or above
Three phase:
5kVA or above

All voltage including
low voltage, highvoltage, ultra highvoltagePrimary voltage:
6 kV, 3 kV class
Secondary voltage:
100 to 600 V

Principle of transformers

E1
E2

=

N1
N2

Iron core
コア）
鉄心（(core)

Magneticflux
磁束Primarycoil
一次コイル

Secondary
二次コイルcoil

Current
Ie
電流
Ie
Number数
タNumberーン数 ターンof turns of turns
N1 N1
N2 N2

Figure I.5

Voltage
電 圧 VV2
2

Transformers convert the level ofvoltage and current by means of
inducing electro motive force in thewindings utilizing the changes ofmagnetic flux flowing through the core
based
on
the
principleofelectro-magnetic induction
When there is no load connected, if
voltage V1 is impressed on the primarycoil, minimal alternating current Ie
flows through the primary coil which
has been wound around the core for N1
times, and alternating flux is generated
in the core in proportion to Ie x N1.
This flux induces voltage in thesecondary coil.
Ie is called excitation current. The
ratio of primary voltage to secondary
voltage is equal to the ratio of numberof turns of primary coil to the number ofturns of secondary coil.

Voltage
電 圧 V1V1

2.2

Principle of transformers(without load)

・・・・・・・・・・・・・・・・・(1Iron core
鉄心（コア）(core)The moment the voltage is impressed,large current flows and it is stabilized
to the above mentioned Ie a few dozen
cycles later.
This phenomenon is
unique to transformers and called
energizing inrush current.
It maybecome a few dozen times greater than
the rated current even if there is noload, so it is necessary to makeprotective coordination in order toprevent the breaker of primary sidefrom being mistripped.
If load is connected to the secondary
winding and current I2 flows, current
I1 flows in inverse proportion to thenumber of turns.

I1
I2

=

N2
N1

Magnetic束
flux
Primary coil
一次コイル

Secondary
coil
二次コイル

I1

Number
ターン数
of turns
N1N1

Number
ターン数
of turns
N2 N2

Current
電流I2
I2

VoltageV2
電圧V2

Voltage
V1
電圧V1

Current
電流I1Principleof transformers
トランスの原理
Current x Number of turns is first
電流×巻回数を一旦磁束に変換
converted to the magnetic flux
I1・N1=I2・N2
I1･N1 = I2･N2 V1/N1=V2/N2
V1/N1 = V2/N2
Capacity(VA) = I1･V1 = I2･V2
容量(VA)=I1･V1=I2･V2

Figure I.6 Principle of transformers(with load)

・・・・・・・・・・・・・・・・・(2(Practically, as for the primary current, the excitation current Ie needs to be added to
I1 in the above mentioned formula; however, it can be disregarded because Ie is
minimal. Meanwhile, if load is connected, the secondary voltage V2 slightly drops
from the level at the time of no-load.)

40

Load
負荷

From formulae (1) and (2) above, the following relational formula (3) isintroduced.
Voltage × Current of the primary and secondary are almost equal.

V1×I1=V2×I2 ・・・・・・・・・・・(3)Figure I.5 and Figure I.6 show the principle of single-phase transformers,
where the primary coil and secondary coil are presented in a state of woundaround the core respectively. However, in the winding structure of actual
transformers, both the primary coil and secondary coil are placed concentricallyaround the core.

Secondary coilCore

Figure I.7

Primary coil

Cross section of transformer’s winding (coil)41

2.3 Causes for generation of loss and improvement measures
There is resistance in the windings in actual use and loss is generated if
current flows there. This is generated depending on the amount of load
current in the secondary side and called load loss.
Meanwhile, eddy current loss and hysteresis loss are generated in the corewhen alternating flux flows. These losses have nothing to do with the amountof load and are called no load loss.
A transformer is stationary equipment consisting of cores where magnetic
flux flows and windings where current flows.
Energy efficiency oftransformers has been improved so far by advancing the technologies forwindings and cores.
Main technologies for reducing loss are as follows.
(1) Reduction of no load loss(i) Adoption of low loss magnetic steel sheets
For magnetic steel sheets as a material of core, high orientation
magnetic steel sheets which have enhanced the crystal orientation ormagnetic domain control magnetic steel sheets which have segmented
magnetic domains by surface grooving are used. The thickness of thesematerials is 0.23 mm which is thinner than conventional materials,
reducing both eddy current loss and hysteresis loss; and the iron loss has
been improved by 31 to 35% in comparison to regular oriented magnetic
steel sheets which had conventionally been used widely, as shown in Table
I.2 below.
Table I.2

Typical characteristic values of core materials

Types of magnetic steel sheet(Classification No. of JIS C 2553)
Regular oriented magnetic steel
sheet (35G130)
High orientation magnetic steel
sheet (23P090)
Magnetic domain control magnetic
steel sheet (23R085)

Sheet thickness(mm)Iron loss (W/kg)
at 1.7 T 50 Hz

0.35

1.28 (100%)0.23

0.88 (69%)

0.23

0.83 (65%)(ii) Improvement of core structure
To improve the no load loss, methods of reducing magnetic resistanceare effective, which can be realized by making cores smaller, making
magnetic flux flow smoothly by improving joint of cores, preventing theworsening of characteristics by processing the magnetic steel sheets, etc.
As regards the Top Runner transformers, efforts are being made to
reduce the no load loss by making cores smaller and making core joints
fewer as a result of expanded adoption of wound cores shifting from piled
cores as well as by rectifying the magnetic flux by adopting step lap
jointing.
42

Stacked core

Wound core

Butt lap joint

Step lap joint

Figure I.8

Improvement of core structure(2) Reduction of load loss
Load loss is the total of resistance loss ofwinding conductor, eddy current loss and thestray losses generated at areas other thanwindings, and the following measures aretaken to reduce the load loss.
(i) Adoption of copper material
For the conductor of windings,
aluminum or copper is used. Because
electric conductivity of copper is higher
than that of aluminum, copper isincreasingly used in order to reduce theresistance loss. Also, adoption of copper
helps to downsize cores since it can makewindings compact.
43

50 Hz

Iron loss (W/kg)(iii) Optimization of magnetic flux density
Since the iron loss changes inproportion to frequency and flux density,
the no load loss can be reduced bylowering the flux density.
However, doing so may make thetransformer larger and increase thenumber of windings; thus, adoption ofthis method shall be determined in
optimaldesigningofanentiretransformer.

60 Hz

Figure I.9 Example of iron loss ofmagnetic steel sheet
Magnetic flux density (T)Table I.9 Example of iron loss
characteristics of magnetic steel sheets

Table I. 3

Loss of Aluminumand Copper

Material
Aluminum

CopperCross
section
100

Loss
100

75

83

85

73

95

65

100

62

(iii) Use of nonmagnetic materials forstructure
Nonmagnetic stainless or insulationmaterials are used for some parts of thesteel sheets to reduce the stray loss
generated by the magnetic flux flowing
throughwindings
orconnected
conductors.
(iv) Enlargement of winding’s cross section
By increasing the cross section area ofwinding conductors and lowering thecurrent density, the resistance loss canbe reduced. However, adoption of thismethod likely leads to upsizing ofwindings and cores; thus, it shall be
determined in the optimal designing ofan entire transformer.

44

Conductor in alternating current magnetic field

Over current

Conductor

Conductor
width

Magnetic flux

Segmentalization and dislocation of conductor

Straight angle conductor

Direction of magnetic flux(ii) Downsizing of windings andsegmentalization of conductors
Efforts to make windings morecompact is being undertaken by use of
insulation technologies such as thinnerinsulation (high-strength paper or film),
technologies for cooling windings, anddownsizing of cores, which results in
reduction of resistance loss. Since eddy
current loss increases in proportion to
the width of conductor which is
positioned at right angle to the magnetic
flux, the conductor is segmentalized forfurther dislocation to reduce the loss.

Segmentalization

Dislocation<No dislocation>
Magnetic flux
Circulation
current<Dislocated>
Magnetic flux

Figure I.10 Segmentalization anddislocation of conductor

II. Shipment Status of Transformers
1. Shipment status by type1.1 State of oil-immersed transformers
Production of oil-immersed transformers steadily grows in the 1980s, but as
equipment investment decrease, it also starts to drastically decrease from thepeak, i.e. 160 thousand units in 1991, down by half to 80 thousand in 1999, andto approximately 70 thousand units in 2008.
While the average capacity per unit is 147 kVA in the 5 year period fromFY1996 to FY2000 and remains on almost the same level as 148 kVA in the 5year period from FY2001 to FY2005, it drastically increases to 206 kVA in
FY2008.
As reasons for such phenomena, quantitative integration and capacity
expansion of transformers when renewing old facilities for the purpose ofenergy saving, appearance of large-scale shopping centers, and construction offactories mainly with semiconductors are considered. Therefore, although thetotal capacity started to recover, a drastic demand decrease becomesremarkable in FY2009, resulting an estimated demand decrease by around 30%
in comparison to the preceding year.

180
Quantity (Thousand units)

160

Target fiscal year
for transformers as
specifiedequipment

140

（

台 120
数
100
千 80
台
60
）

40
20
0
1970

72

74

76

78

1980

82

84

86

88

1990

92

94

96

98

2000

02

04

06

08

Fiscalyear
年度

Figure II.1

Quantitative transition of oil-immersed transformers

25

Target fiscal year
for transformers
as specified
equipment（

Capacity (Million kVA)

容 20
量

）

百 15
万
ｋ
10
Ｖ
Ａ
5
0
1970

72

74

76

78

1980

82

84

86

88

1990

92

94

96

98

2000

02

04

06

08

Fiscalyear
年度

Figure II.2

Transition of total capacity of oil-immersed transformers

Source: (1) Statistical survey of production dynamics by Ministry of Economy, Trade andIndustry, (2) Survey by Japan Electrical Manufacturers’ Association45

1.2 State of encapsulated-winding transformers
Thanks to the increase of demand for flame retardant power receiving anddistributing facilities, production of encapsulated-winding transformers is
stable at between 12 thousand units and 14 thousand units from 1987, but it
starts to drastically decrease from 1998.
The reasons for this are presumed to be the decrease of building and public
facility constructions and the partial demand shift to inexpensive oil-immersed
transformers. Later, recovery can be noted in the period from 2004 to 2006.
The average capacity per unit shows a slight increase from 283 kVA in the 5year period from FY1997 to FY2001 to 300 kVA in the 5 year period from
FY2002 to FY2006, and it is drastically increased up to 392 kVA in FY2008.
As reasons for such phenomena, floor capacity increased as spread of
air-conditioners multi control system for buildings, appearance of large-scalebuildings, and construction of large-scale database centers are considered.
Therefore, although the total capacity starts to recover, like oil-immersed
transformers, a drastic demand decrease becomes remarkable in FY2009,
resulting an estimated demand decrease by around 20% in comparison to thepreceding year.

16

Target fiscal year
for transformers as
specifiedequipment

Quantity (Thousand units)

14

（

12
台
数 10
8

）

千
台

6
4
2
0
84

86

88

1990

92

94

96

98

2000

02

04

06

08

Fiscalyear
年度

Figure II.3

Quantitative transition of encapsulated-winding transformers
Target fiscal year
for transformers
as specified
equipment

4 .5
4 .0
（

Capacity (Million kVA)

容 3 .5
量3 .0）

百 2 .5万ｋ 2 .0Ｖ 1 .5
Ａ
1 .0
0 .5
0 .0
84

86

88

1990

92

94

96

98

2000

02

04

06

08

Fiscalyear
年度

Figure II.4

Transition of total capacity of encapsulated-winding transformers

Source: (1) Statistical survey of production dynamics by Ministry of Economy, Trade andIndustry, (2) Survey by Japan Electrical Manufacturers’ Association46

2. Status of number of transformers installed
Service life of transformers is much longer than that of other equipment, sotransformers made before designation as special equipment are still being
used.
Average service years of transformers are said to be 26.2 years in case ofoil-immersed transformers and 25.7 years in case of encapsulated-windingtransformers, and there are many transformers which are being used for morethan 30 years. Thus, the renewal of existing equipment is not so active
because economy has slowed down and because measures for the detoxificationof low density PCB are unclear, etc. The remaining quantity of transformers
with poor energy consumption efficiency which have existed before JIS C 4304
and 4306 (2005) incorporating the first evaluation standards is estimated as
2.78 million units as of 2010. Of them, approximately 950 thousand units arethose which have been used for more than 20 years that is a recommended
timing to replace with a new unit, and they are still expected to be utilized even
now.

200
180
160
140
120
100
80
60
40
20
0

2008
Quantity = 38 thousand units, Total capacity = 10737 MVA,
Average capacity, 283 kVA
1995 to 1999 average
Quantity = 49 thousand units, Total capacity = 9766 MVA,
Average capacity, 200 kVA

Number of units remaining,
2.78 million

残存台数278万台

Encapsulated-winding
モールド変圧器
transformers

Number of units
廃却済み台数
disposed of'70 '72 '74 '76 '78 '80 '82 '84 '86 '88 '90 '92 '94 '96 '98 '00 '02 '04 '06

Figure II.5

Remaining number of transformers existed before
first evaluation standard

Source: Survey by Japan Electrical Manufacturers’ Association47

3. Shipment status by capacity
As regards the shipment status by capacity, the survey was conducted incollaboration with the member companies of the Japan Electrical
Manufacturers' Association.
3.1 State of oil-immersed transformers
According to the actual shipment in FY 2008, the number of manufactured
unit of single phase 200 kVA or below and that of three phase 300 kVA or below
are both decreasing compared with the average shipped units during the period
from FY1995 to FY1999. On the other hand, the number of manufactured
unit of single phase 300 kVA or above and that of three phase 500 kVA or above
are increased, showing that the capacity distribution is shiftingt to the larger.
1 2 ,0 0 0

FY2008
2008年実績
Average of FY1995 to
1995～1999年平均
FY19991 0 ,0 0 0
Quantity/year

台
数
／
年

FY2008Quantity = 31 thousand units, Total capacity =3370 MVA, Average capacity, 110 kVA
FY1995 to FY1999 average
Quantity = 48 thousand units, Total capacity =4181 MVA, Average capacity, 87 kVA

8 ,0 0 0
6 ,0 0 0
4 ,0 0 0

2000

1500

1000

750

500

300

200

150

100

75

50

30

20

15

10

7.5

5

0

3

2 ,0 0 0

Capacity(kVA)
容 量 （ kVA)

Figure II.6

Transformers (oil-immersed) FY2008 shipment quantity
by capacity (single phase)
Source: Survey by Japan Electrical Manufacturers’ Association

FY2008
2008年実績
Average of FY1995 to
1995～1999年平均
FY1999

2000

1500

1000

750

500

300

200

150

100

75

50

30

20

15

10

7.5

5

3

Quantity/year

9 ,0 0 0
8 ,0 0 0
7 ,0 0 0
台 6 ,0 0 0
数 5 ,0 0 0／ 4 ,0 0 0
年 3 ,0 0 0
2 ,0 0 0
1 ,0 0 00Capacity(kVA)
容 量 （ kVA)

Figure II.7

Transformers (oil-immersed) FY2008 shipment quantity
by capacity (three phase)
Source: Survey by Japan Electrical Manufacturers’ Association48

3.2 State of encapsulated-winding transformers
According to the actual shipment in FY2008, the number of manufactured
units of single-phase transformers of all capacity and that of three-phasetransformers of 300 kVA or below are both decreased compared with theaverage shipped units during the peirod from FY1995 to FY1999.

2000

1500

1000

750

500

300

200

150

100

75

50

30

20

15

10

7.5

3

5

FY2008
2008年実績
Average of FY1995 to
1995～1999年平均
FY1999Quantity/year

900
800
700
台 600
数 500
／ 400
年 300
200
100
0

FY2008Quantity = 3.0 thousand units, Total capacity =605 MVA, Average capacity, 205 kVA
FY1995 to FY1999 average
Quantity = 4.5 thousand units, Total capacity =846 MVA, Average capacity, 189 kVA

Capacity(kVA)
容量（kVA)

Figure II.8

Transformers (encapsulated-winding) FY2008 shipment
quantity by capacity (single phase)
Source: Survey by Japan Electrical Manufacturers’ Association

FY2008
2008年実績
Average of FY1995 to
1995～1999年平均
FY1999

2000

1500

1000

750

500

300

200

150

100

75

50

30

20

15

10

7.5

5

3

Quantity/year

1,800
1,600
1,400
台 1,200
数 1,000
／ 800
年 600
400
200
0

Capacity(kVA)
容量（ kVA)

Figure II.9

Transformers (encapsulated-winding) FY2008 shipment
quantity by capacity (three phase)
Source: Survey by Japan Electrical Manufacturers’ Association

49

Reference 2

Achievement Status of Power Transformers
1. State of Achievement(1) Improvement ratio estimated when developing current standard
Energy consumption efficiency calculated as a weighted average per unit
using the actual shipment in FY1999 is 818 W, and energy consumption
efficiency calculated as a weighted average of target standard values is 570 W
supposing that the number of units shipped and the product constitution in thetarget fiscal year remain the same as those noted when preparing the Top
Runner standards for transformers. And the improvement ratio estimatedbased on this is 30.3%.
(2) Improvement achieved in target fiscal year
Energy consumption efficiency calculated as a weighted average value using
the number of units shipped is 636 W for oil-immersed transformers whichreached the target fiscal year in FY2006; and it is 1,350 W for
encapsulated-winding transformers which reached the target year in FY2007.
Taking into consideration the above, the improvement ratio of energy
consumption efficiency based on the actual shipment in the target fiscal year
becomes as follows using 711W the weighted average value of transformer as awhole.
{(818 W − 711 W)/818 W} × 100 = 13.1%
The achievement is lower than the estimated improvement because thecapacity of transformers used in facilities is becoming larger in recent years.
Evaluations made taking into consideration the product constitution is
described in section 2 below.

2. Change of product constitution(1) Transition of average capacity
A weighted average capacity calculated with the number of units shipped isdrasticallyincreasingforbothoil-immersed
transformers
andencapsulated-winding transformers, indicating that the trend of shipment isshifting from products with smaller rated capacity to those with larger capacity.

50

(2) Improvement ratio by rated capacity
To make evaluation excluding the effect of large capacity, improvement ratio
is calculated for each rated capacity, and their simple averages are shown in
Table 1 below.
Improvement ratio of energy consumption efficiency is 34.0% for
oil-immersed transformers, 26.8% for encapsulated-winding transformers and32.8% for transformers as a whole.
Thus, energy saving performance of transformers for each capacity has been
improved as a result of efforts for energy saving made by manufacturers, etc.,
so it is thought that the current standards based on the idea of Top Runnermethod are working effectively.
Table 1

Improvement ratio by rated capacity and simple average by categoryof single-phase transformers
Oil-immersed transformers

Phase

Capacity(kVA)

Frequency(Hz)

Improvement
ratio bycapacity

Improvement
ratio bycategory

Encapsulated-windingtransformers
Improvement Improvement
ratio byratio bycapacity
category
34.6%

10

20.7%

20

22.1%

35.9%

30

24.0%

32.3%

50

26.5%

29.2%

75
100

50

28.5%
29.8%

30.1%

29.1%
29.4%

150

31.7%

28.3%

200

33.0%

27.3%

300

35.5%

27.7%

Single

500

38.2%

26.3%

phase

10

18.3%

33.2%

20

21.1%

35.7%

30

24.6%

32.9%

50

26.2%

28.9%

75
100

60

28.9%
30.1%

30.7%

30.3%
30.0%

150

32.7%

30.2%

200

34.1%

29.2%

300

36.9%

27.9%

500

39.0%

26.2%

51

27.9%

28.6%

Table 2

Phase

Improvement ratio by rated capacity and simple average by categoryof three-phase transformers

Capacity(kVA)

Frequency(Hz)

Oil-immersed transformers
Improvement Improvement
ratio byratio bycapacity
category

Encapsulated-windingtransformers
Improvement Improvement
ratio byratio bycapacity
category

20

26.8%

34.2%

30

26.4%

35.9%

50

27.3%

32.0%

75

30.0%

30.4%

100

31.3%

28.9%

150

32.8%

27.2%

200

50

34.1%

34.0%

27.5%

300

35.9%

26.4%

500

38.5%

24.6%

750

36.6%

26.0%

1000

34.4%

25.9%

1500

32.9%

26.8%

Three

2000

31.2%

27.9%

Phase

20

25.9%

31.6%

30

26.9%

34.5%

50

29.4%

32.4%

75

31.7%

31.2%

100

33.4%

27.9%

150

35.0%

26.1%

200

60

37.3%

36.6%

25.7%

300

39.3%

25.3%

500

41.4%

22.0%

750

37.7%

26.9%

1000

36.1%

27.7%

1500

36.1%

28.5%

2000

35.3%

29.5%

26.6%

25.9%

*1 Each datum is based on the survey of actual shipment in FY1999 and FY2008
conducted by the Japan Electrical Manufacturers’ Association.
*2 Products of standard specification products defined in JIS C4304 and JIS C4306 areorganized.
*3 As for the improvement ratio by category, it is estimated based on an assumption thatthe product constitution is the same for the actual shipments in 1999.

52