SIST EN 60034-2:1999
(Main)Rotating electrical machines -- Part 2: Methods for determining losses and efficiency of rotating electrical machinery from tests (excluding machines for traction vehicles)
Rotating electrical machines -- Part 2: Methods for determining losses and efficiency of rotating electrical machinery from tests (excluding machines for traction vehicles)
Applies to d.c. machines and to a.c. synchronous and induction machines. The principles can be applied to other types of machines such as rotary converters, a.c. commutator motors and single-phase induction motors for which other methods of determining losses are used.
Drehende elektrische Maschinen -- Teil 2: Verfahren zur Bestimmung der Verluste und des Wirkungsgrades von drehenden elektrischen Maschinen aus Prüfungen (ausgenommen Maschinen für Schienen- und Straßenfahrzeuge)
Machines électriques tournantes -- Partie 2: Méthodes pour la détermination des pertes et du rendement des machines électriques tournantes à partir d'essais (à l'exclusion des machines pour véhicules de traction)
S'applique aux machines à courant continu ainsi qu'aux machines à courant alternatif, synchrones et à induction. Les principes peuvent être adoptés pour d'autres types de machines telles que les commutatrices, des moteurs à collecteur et les moteurs à induction monophasés pour lesquels on applique en général d'autres méthodes de détermination des pertes.
Rotating electrical machines - Part 2: Methods for determining losses and efficiency of rotating electrical machinery from tests (excluding machines for traction vehicles) (IEC 60034-2:1972 + IEC 60034-2A:1974)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 60034-2:1999
01-april-1999
Rotating electrical machines - Part 2: Methods for determining losses and
efficiency of rotating electrical machinery from tests (excluding machines for
traction vehicles) (IEC 60034-2:1972 + IEC 60034-2A:1974)
Rotating electrical machines -- Part 2: Methods for determining losses and efficiency of
rotating electrical machinery from tests (excluding machines for traction vehicles)
Drehende elektrische Maschinen -- Teil 2: Verfahren zur Bestimmung der Verluste und
des Wirkungsgrades von drehenden elektrischen Maschinen aus Prüfungen
(ausgenommen Maschinen für Schienen- und Straßenfahrzeuge)
Machines électriques tournantes -- Partie 2: Méthodes pour la détermination des pertes
et du rendement des machines électriques tournantes à partir d'essais (à l'exclusion des
machines pour véhicules de traction)
Ta slovenski standard je istoveten z: EN 60034-2:1996
ICS:
29.160.01 Rotacijski stroji na splošno Rotating machinery in
general
SIST EN 60034-2:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 60034-2:1999
CEI
NORME
INTERNATIONALE IEC
34-2A
INTERNATIONAL
Première édition
STANDARD
First edition
1974
Premier complément à la Publication 34-2 (1972)
Machines électriques tournantes
Deuxième partie:
Méthodes pour la détermination des pertes et du rendement
des machines électriques tournantes à partir d'essais
(à l'exclusion des machines pour véhicules de traction)
Mesure des pertes par la méthode calorimétrique
First supplement to Publication 34-2 (1972)
Rotating electrical machines
Part 2:
Methods for determining losses and efficiency
of rotating electrical machinery from tests
(excluding machines for traction vehicles)
Measurement of losses by the calorimetric method
CEI 1974 Droits de reproduction réservés — Copyright — all rights reserved
©
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cédé, électronique ou mécanique, y compris la photocopie et including photocopying and microfilm, without permission
les microfilms, sans l'accord écrit de l'éditeur. in writing from the publisher.
Genève, Suisse
Bureau Central de la Commission Electrotechnique Internationale 3, rue de Varembé
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SIST EN 60034-2:1999
3
CONTENTS
Page
FOREWORD 5
PREFACE 5
INTRODUCTION 7
3.1 List of symbols 7
SECTION ONE — GENERAL
Clause
1. General 9
2. Determination of losses Pl by measurement of the volume rate of
flow and rise in temperature of the
cooling medium 9
3. Losses PI measured electrically using the calorimetric calibration method 9
4. Stable conditions 11
5. Losses Pz
not transmitted to the cooling medium 11
6.
Losses external to the reference surface
Pe 13
SECTION
Two — WATER AS THE COOLING MEDIUM
7. Application and basic relationship 15
8. Measurement of water flow 15
9. Measurement of the temperature rise of the water 17
10. Measuring accuracy 19
SECTION THREE — AIR AS THE COOLING MEDIUM
11. Application and basic relationship 19
12. Determination of the mass rate of flow 21
13. Measurement of the temperature rise of the air 25
14. Determination of the specific heat capacity of the air 25
15. Measuring accuracy 25
SECTION FOUR — PRACTICAL CONSIDERATIONS
16.
Preparations for calorimetric measurements with liquid coolants 27
17. Connections and equipment for calorimetric measurements with liquid coolants 29
FIGURES 30
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SIST EN 60034-2:1999
— 5 —
INTERNATIONAL ELECTROTECHNICAL COMMISSION
FIRST SUPPLEMENT TO PUBLICATION 34-2 (1972)
Rotating electrical machines
Part 2 : Methods for determining losses and efficiency of rotating electrical machinery from tests
(excluding machines for traction vehicles)
Measurement of losses by the calorimetric method
FOREWORD
1) The formal decisions or agreements of the I E C on technical matters, prepared by Technical Committees on which all the National
Committees having a special interest therein are represented, express, as nearly as possible, an international consensus of opinion
on the subjects dealt with.
2) They have the form of recommendations for international use and they are accepted by the National Committees in that sense.
3) In order to promote international unification, the I EC exp
resses the wish that all National Committees should adopt the text of the
I EC recommendation for their national rules in so far as national conditions will permit. Any divergence between the I EC recom-
mendations and the corresponding national rules should, as far as possible, be clearly indicated in the latter:
PREFACE
This recommendation has been prepared by Sub-Committee 2D, Losses and Efficiency, of I E C Technical
Committee No. 2, Rotating Machinery.
It forms the first supplement to I E C Publication 34-2, Rotating Electrical Machines, Part 2: Methods for Deter-
mining Losses and Efficiency of Rotating Electrical Machinery from Tests (Excluding Machines for Traction
Vehicles).
A first draft was discussed at the meetings held in London in 1968 and in Bucharest in 1970. As a result of this latter
meeting, a final draft, document 2D(Central Office)17, was submitted to the National Committees for approval
under the Six Months' Rule in August 1971. Amendments, document 2D(Central Office)19, were submitted to the
National Committees for approval under the Two Months' Procedure in February 1973.
The following countries voted explicitly in favour of publication:
Australia Portugal
Austria Romania
Belgium South Africa (Republic of)
Denmark Spain
Egypt Sweden
Finland Switzerland
France Turkey
Germany Union of Soviet
Israel Socialist Republics
Italy United Kingdom
Japan United States
Norway of America
Poland Yugoslavia
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SIST EN 60034-2:1999
7
FIRST SUPPLEMENT TO PUBLICATION 34-2 (1972)
Rotating electrical machines
Part 2 : Methods for determining losses and efficiency of rotating electrical machinery from tests
(excluding machines for traction vehicles)
Measurement of losses by the calorimetric method
INTRODUCTION
The calorimetric method can be used to determine the efficiency of electrical rotating machinery:
— either by the determination of the total losses on load,
or by the determination of the segregated losses and hence the conventional total loss by summation of the
—
segregated losses.
Depending upon the circumstances, calorimetric measurements may be made in two different ways:
— either by measuring the quantity and rise in temperature of the cooling medium (direct method),
or by calibration of the rise in temperature of the cooling medium.
—
The calorimetric measurements should be performed for each cooling circuit, either primary or secondary,
separately.
The methods of loss determination given in this recommendation have been devised mainly for large generators,
but the principles used can also be applied to other machines.
Page 9
3.1 List of symbols
Complete the existing list of symbols by the following:
P; = losses inside reference surface
losses outside reference surface
Pe =
P1 = losses which are dissipated by the cooling circuits in the form of heat and which can be measured calori-
metrically
losses not transmitted to the cooling medium but which are dissipated through the reference surface by con-
P2 =
duction, convection, radiation, leakage, etc.
cp = specific heat capacity of the cooling medium
O = volume rate of flow of the cooling medium
= density of the cooling medium
At = rise in temperature of the cooling medium or temperature difference between the machine reference surface
and the external ambient temperature
y = exit velocity of cooling medium
a = discharge coefficient
Pl and Py
e = error in measurement of losses,
h = coefficient of heat transfer
Ap = difference between the static pressure in the intake nozzle and ambient pressure
A = cross-sectional area of the intake nozzle
= temperature
tl = inlet temperature of the cooling medium
t2 = outlet temperature of the cooling medium
b = barometric pressure
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SIST EN 60034-2:1999
— 9 —
Page 53
Replace Clause 17 by the following:
SECTION ONE — GENERAL
1. To enable a classification of the total losses to be made, a " reference surface " is defined for the machine.
(Pi) are dissipated
This is a surface completely surrounding the machine such that all losses produced inside it
through it to the outside (see Figure 1, page 30).
The total losses of the machine consist of:
— losses inside the reference surface Pi,
— losses outside the reference surface Pe.
can be divided into two categories:
The losses inside the reference surface P i
Pi =P,±
P2
= being losses which can be measured calorimetrically and which are dissipated in the form of heat by the
P,
cooling circuits. These constitute the major part of the losses (internal losses which can be measured);
P2 = being losses not transmitted to the cooling medium and which are dissipated through the reference surface
by conduction, convection, radiation, leakage, etc. These constitute a small part of the total losses and can
be calculated (internal losses which cannot be measured).
ce.
Note. — P2 may be negative and therefore subtracted when heat flows into the reference surfa
may form part of the specified losses and should then be measured
Losses external to the reference surface
(Pe)
separately.
Note. — Losses in the bearings inside the reference surfa ce are included in the losses Pi.
2. Determination of losses Pl by measurement of the volume rate of flow and rise in temperature of the cooling medium
In stable operating conditions, and when thermal equilibrium has been achieved, the losses dissipated by the
cooling medium are:
P1=cpQeOt kW
where:
cp = specific heat capacity of the cooling medium in kJ/(kg K) at pressure p
Q = volume rate of flow of the cooling medium in ms/s
e = density of the cooling medium in kg/m $ at the temperature at the point of flow measurement
At = rise in temperature of the cooling medium in deg K.
If the cooling medium is water, the method of measurement is covered in Section Two.
If the cooling medium is air, the method of measurement is covered in Section Three.
losses may be measured using oil as a cooling medium, but it is preferred to measure on the water side of an oil-to-
Note. —Bearing
water heat exchanger because the thermal characteristics of water are better known.
measured electrically using the calorimetric calibration method
3. Losses Pi
3.1 General
In this method, a calibration curve relating the rise in temperature of the cooling medium to the losses dissipated
in the machine is determined by tests carried out under such conditions that the losses P i can be measured directly
P2 provided the conditions during
by electrical methods. This method does not require the evaluation of the losses
the tests are correctly adjusted, and this method may be used when direct calorimetric measurement of the cooling
circuit is impossible or when difficulties are encountered in putting it into practice.
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SIST EN 60034-2:1999
— 11 —
3.2 Generation of losses for calibration
The machine losses shall be derived from an electrical power source to enable them to be measured accurately.
They can be produced inside the machine, either
a) in the form of normal machine losses, i.e. by supplying the
machine in the normal way and running it in the unloaded or loaded condition depending upon the losses required,
or
b) in the form of thermal losses from a special resistor inserted into the machine for the test in such a manner
that the losses produce a heat flow pattern similar to that occurring in the machine under normal conditions.
It is essential, for maximum accuracy, that the magnitude of losses used to obtain the calibration curve embraces
the values which it is desired to measure by the calorimetric calibration method. Where this cannot be achieved,
extrapolation of the calibration curve shall be the subject of agreement.
3.3 Measurement of actual losses
When the calibration curve has been obtained, the machine is run in the same condition, but with the losses which
it is required to measure being generated in it. Measurement of the coolant temperature rise and reference to the
calibration curve then enables this to be done.
3.4
Conditions to be met during calibration and test
The machine shall be in the same physical condition during both these runs, i.e. with the same enclosure, cooling
and mounting arrangements. The surrounding temperature and ambient conditions should also be kept as nearly
similar as possible. The flow of coolant should be kept the same with its " cooled " temperatures as close as possible.
Stable conditions as described in Clause 4 should be reached before final test values are measured and the con-
ditions defined in Sections 1, 2 and 3 shall be complied with where relevant to this method.
4. Stable conditions
Provided that the operating conditions and inlet temperature of the cooling medium are sufficiently stable,
thermal equilibrium can be considered to have been achieved when measurements of rise in temperature and the
volume rate of flow of the cooling medium indicate that the losses are constant to within ± 1 % over a period of
two hours, or when the temperature rise of the cooling medium does not vary by more than + 1 % in one hour,
the volume rate of flow being constant.
If the inlet temperature of the cooling medium or the temperature of the windings varies by more than ± 0.3 °C
per hour, it may be very difficult to achieve thermal equilibrium. In such cases, a lower value should be aimed for. For
the calorimetric measurement of air, this condition may be regarded as a criterion of thermal stability. However,
for the determination of total losses or when close tolerances on measurement are not required, a variation of
+ 0.5 °C per hour is permissible.
If the inlet temperature of the cooling medium does not conform to the conditions specified above, it may be
necessary to postpone the tests until more suitable conditions prevail.
For guidance, the duration of the test will vary depending upon the method of measuring the losses, and is likely
to be from 10 h to 20 h for the determination of losses at full load, and from about 15 h to 30 h for the determi-
nation of losses at no load.
5. Losses P2
not transmitted to the cooling medium
These losses consist of:
— the losses dissipated in the foundations and in the shaft by conduction; these are usually negligible and very
difficult to measure,
— the losses caused by contact of the external surfaces of the machine with the surrounding atmosphere (convection)
and with the housing (radiation),
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SIST EN 60034-2:1999
— 13 —
— the losses due to variation in the kinetic energy of the cooling air circulating in a machine having an open-circuit
cooling system. These losses are generally small, but can be calculated using the formula:
P V2 kW
2 000
where:
Q = volume rate of flow of air in me/s
e = density of air in kg/m3
v = exit velocity of air in m/s.
To reduce losses P2
(including those due to leakage) to a minimum, the test conditions may be improved by
varying either the volume rate of flow or the temperature of the cooling medium in order to reduce the difference
in temperature between the system and the ambient air. Care should be taken, however, to ensure that the accuracy
of the temperature measurements is not affected by the temperature of the surroundings. These precautions are
essential in the measurement of separate losses.
The losses P2 can be minimized by suitable lagging of the radiating surfaces or portions of the machine, the
known heat transmission properties of the lagging material being taken into account in the calculations. This
method is particularly suited to locations where it is difficult to suppress external air current or to maintain relatively
constant ambient temperature conditions.
In practice, by conducting the tests in such a way that the losses P2 are less than 2.5% of the losses P measured
i
at full load, and less than 5% of the losses P
i determined by the method of separate loss measurements, only the
losses dissipated at the surface of the machine need to be taken into consideration. These losses may be obtained
from the formula:
Loss 132 = h X area (m e) x At (K)
where:
At = temperature difference between the machine reference surface and the external ambient air temperature.
It is recognized that h
for losses dissipated by the surface is between 10 W and 20 W/(m 2 K), a reasonable figure
being 15 W/(m 2
K) when the precaution has been taken of eliminating air currents over the transfer surfaces. The
factor to be used should be agreed between manufacturer and purchaser.
Examples for determining
h for losses dissipated from surfaces in contact with air are:
— for external surfaces h = 11 -J- 3 y W/(m 2 K)
where: y = velocity of ambient air in m/s, and
— for surfaces entirely within the machine's external surface:
h = 5 + 3 y W/(m 2 K)
where: y = velocity of cooling air in m/s (see Figure 1, page 30).
6. Losses external to the reference surface Pe
The losses consist mainly of the following:
Pe
—
losses in the rheostat in the main excitation circuit, in voltage regulation, shunt and excitation circuits independent
of the exciter,
— losses in the exciter and the slip-rings when their cooling circuits are independent of that of the main machine,
— losses by friction in the bearings, either wholly or partially depending on whether they are wholly or partly
outside the reference surface.
The above losses, evaluated separately, shall be added to the internal losses Pi.
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SIST EN 60034-2:1999
— 15 —
SECTION TWO - WATER AS THE COOLING MEDIUM
7. Application and basic relationship
This method is applicable only to machines provided with a closed primary cooling system and using water as a
secondary coolant, but it gives a very practical and accurate method of measurement. Typical connection diagrams
for parallel and series connected coolers are given in Figures 2 and 3, page 31.
The losses dissipated by the water are given in the following formula:
P cpe Q At kW
1_=
where:
p = 0.1 MN/m2) determined from
cp = specific heat capacity of the water in kJ/(kg K) (at constant pressure
t, and outlet temperature t2
Figure 4, page 32, as the integrated mean value of cp, between inlet temperature
of the water
3) shown on the curve in Figure 4 at the point where the rate of flow Q (m3/s) is meas-
e = density of water (kg/m
ured
the temperature rise of the water in K.
At = t2 — t1,
e, particularly if the cooling water
Where there is any doubt as to the accuracy of the factors employed for cp and
contains salts, it will be necessary for cp and a to be measured.
The care with which the measurements are made, together with the calibration of the measuring instruments,
is a decisive factor in obtaining accurate results.
Measurement of water flow
8.
To obtain an easily measurable rise in temperature, the flow of water should be controlled by a valve placed
downstream from the flowmeter.
The volume rate of flow of water can be measured by the following methods:
— calibrated tanks,
— weirs and weirs with standardized gates,
— accurately calibrated volume counters,
— electromagnetic or vane type flowmeters,
— orifice plate, venturi meter or nozzles in accordance with ISO Recommendation R541.
8.1 Recommendations for measurement of quantity of water
Measurement by calibrated tanks
8.1.1
The volume of the tank should be such that the filling time is at least one minute.
The dimensions of the tank when its volume is determined by calculation only should be such that the variations
in volume due to water pressure are less than 0.02%.
The volume rate of flow of water through the cooling system should not be affected during measurement.
The time should be measured by using either two stop-watches simultaneously or an electrical timing device.
8.1.2 Measurements using volumetric or velocity type flowmeters
The installation of volumetric or velocity type flowmeters in pipes should be in accordance with manufacturer's
instructions (straight sections up and downstream, position, etc.) and care should be taken that no air bubbles are
present in the water.
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SIST EN 60034-2:1999
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It is recommended that the measuring instruments should be calibrated before and after the measurements in
conditions similar to those prevailing during the measurements, particularly if it is not possible to comply with
the method of installation recommended by the manufacturer of the instrument.
In the case of volumetric measurements, the time should be measured with two stop-watches simultaneously
or by means of an electrical timing device. The measuring time should be long enough to ensure sufficient accuracy
and should be not less than 5 min.
If the measurement is made with a direct reading flowmeter, about 20 readings should be made and an average
value taken.
Note. — It is advisable to determine, by agreement between manufacturer and purchaser, the different points of measurement when
establishing the layout of power plant.
Under certain conditions, it may even be advisable to include means to install and remove the measuring apparatus without
interrupting the operation of the machine (see Figure 9, page 36).
9. Measurement of the temperature rise of the water
The measurement can be made by means of one of the following:
- thermocouples or resistance temperature detectors, preferably platinum, placed directly in the water or in oil-
filled thermometer pockets, and positioned opposite each other so as to obtain direct readings of the temperature
rise of the water. Greater accuracy is obtainable with the use of platinum resistance temperature detectors,
— precision thermometers placed in oil-filled thermometer pockets. In order to reduce error, the thermometers
should be interchanged after each reading and the oil should be maintained at the correct level.
The measuring instruments should be calibrated before and after the tests.
The temperature measurement includes the difference in temperature due to losses in the coolers and associated
pipework between measuring points and is assumed to be 1 deg C for a pressure drop of 4.2 MN/m 2. The loss cor-
responding to the pressure drop should be subtracted from the total losses measured using this method.
It is recommended that a recording instrument be used when the measuring method permits.
9.1 Positioning of thermometer pockets (see Figure 5, page 33)
The thermometer pockets should be as close as possible to, and outside, the generator pit, but at such a distance
from the pit that the equalizing baffle referred to below can be installed.
Where necessary, the water pipes should be lagged to avoid heat transfer to the outside.
The water temperature at the location of the thermometer pockets should be homogeneous. An equalizing
baffle should be installed in order to obtain homogeneous flow. It should have one (or two) 90° elbows together
with a pipe of length of about 20 time the diameter. With more than one cooler, the water flow from each cooler
should be regulated to give the same outlet temperature; alternatively the coolers can be measured separately.
The depth of the thermometer pocket should be between 0.6 and 0.8 times the diameter of the pipe. The walls
should be as thin as possible and of a material having high thermal conductivity.
Installation of the measuring device inside the thermometer pocket
9.2
The measuring instrument should be positioned as close as possible to the wall of the pocket, which should be
partly filled with oil to improve thermal contact. To avoid heat exchange with the air, the pocket should be
provided with a plug.
When the temperature is measured by means of thermocouples or resistance temperature detectors, the leads
should be placed in contact with the outer surface of the pipe for a distance of 25 cm and thermally insulated (see
Figure 5).
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SIST EN 60034-2:1999
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10. Measuring accuracy
Accuracy in the determination of losses by the calorimetric method depends upon the method of measurement
employed, the type of instruments used and any error in estimating losses P2. Two categories of measurement error
are therefore given below in Table I :
— Category A being appropriate to the highest accuracy obtainable,
— Category B being appropriate to an acceptable order of accuracy suitable for the majority of cases.
If the relative error in Pi caused by an error in P2 is likely to be greater than 1.5% in the case of Category A,
or greater than 3 % for Category B, the calorimetric method is not recommended.
Some inaccuracies are common to all measuring methods, for example, the relative dimensions in measurement
of speed, voltage, intensity, etc.
Note. — Measurements made by water calorimetry generally give more accurate results than those made with air. Also, if gas bubbles
are present in the water (these can be detected through an obse rvation window), it is preferable to eliminate them in order to
use the water calorimetric method rather than to use the calorimetric method with air.
TABLE I
Measurement error in calorimetry by water
Effect of error e
as a percentage of Pi
Clause Quantity
Category A Category B
G I
Thermal equilibrium 1)
4
7 Specific heat capacity x water density L 1
8 Volume rate of flow G 1
9 Temperature rise G I
.z
L 0.5 3
( 2)
5 Estimation of P2 losses
G 1.5
Losses Pi : 95% confidence
o
L25
G5
Limits of error = V Eel
1)If thermal equilibrium has not been achieved, the error can be appreciable.
2)The lower figure is valid if all precautions described in Clause 5 are taken. The higher figure for Category A is valid provided that
P2 is less than 5% of Pi.
SECTION THREE — AIR AS THE COOLING MEDIUM
MEASUREMENTS MADE IN THE PRIMARY CIRCUIT
Application and basic relationship
11.
Measurement in the primary circuit requires experience in applied aerodynamics. The method of measurement
to be used will vary according to the size of the plant and the type of ventilation adopted.
Air calorimetry has the advantage of being applicable to all ventilating systems, whether open or closed circuit.
No special measuring instrument has to be incorporated into the machine during assembly. For this reason, measure-
ments made by air calorimetry can also be taken on machines already installed on site and whi
...
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