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IS0
I N T ER N AT I O N A L O R G A N I2 AT I O N FOR S TA N DARD IZATl O N
IS0 RECO M M EN DATIO N
R 700
RATING OF MANUAL ARC WELDING EQUIPMENT
1 st EDITION
'March 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore oniy
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 700, Rating of manual arc welding equipment, was drawn up by
Technical Committee ISOlTC 44, Welding, the Secretariat of which is held by the Association
Française de Normalisation (AFNOR).
Work on this question by the Technical Committee began in 1957 and led, in 1965, to the
adoption of a Draft Is0 Recommendation.
In May 1966, this Draft IS0 Recommendation (No. 973) was circulated to all the IS0 Member
Bodies for enquiry. It was approved, subject to a few modifications of an editorial nature, by the
following Member Bodies :
Australia Ireland Sweden
Belgium Israel Switzerland
Brazil
Japan Turkey
Chile
Korea, Rep. of U.A.R.
Czechoslovakia
Norway United Kingdom
Denmark
Poland U.S.S.R.
France Romania Yugoslavia
Germany South Africa,
Hungary
Rep. of
India
Spain
Five Member Bodies opposed the approval of the Draft :
Canada
Finland
Netherlands
Portugal
U.S.A.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in March 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 700-1968 (E
IS0 Recommendation R 700 March 1968
RATING OF MANUAL ARC WELDING EQUIPMENT *
PART I
GENERAL
1. SCOPE
L
This IS0 Recommendation applies to the following most commonly used types of welding equipment
for manual arc welding :
single operator arc welding generators with drooping characteristics and with associated
(a)
driving equipment (except internal combustion engines);
single operator arc welding transformer equipment, with drooping characteristics.
(b)
It specifies the minimum requirements for establishing a common basis for the rating of such equip-
ment.
NOTE. - Welding apparatus with a drooping characteristic is defined as apparatus having an external static
characteristic (see clause 2.8) which, in its normal operating region, is such that the voltage decreases as the current
increases.
This IS0 Recommendation applies to equipment for use under the following conditions :
Altitude. In the absence of any information in regard to height above sea level at which
(a)
the equipment is intended to work in ordinary service, the altitude is assumed not to
exceed 1000 m (3300 ft).
Temperature of the cooling medium. In the absence of any information to the contrary,
(b)
it is assumed that, in the case of air cooled equipment, none of the following temperature
limits is exceeded :
- maximum ambient air temperature 40 OC
30 OC
- daily average ambient air temperature
- yearly average ambient air temperature 20 OC
2. DEFINITIONS**
2.1 Operating conditions. All quantities defining the performance of a machine, an appliance or
network.
2.2 Rated. Qualifying term applied to a quantity which is used in the specification of the welding
equipment.
*
For the purposes of this IS0 Recommendation, “manual arc welding” implies a reference maximum duty cycle
of 60 ‘b.
** Ail electrical quantities specified in the definitions are those obtained under steady conditions.
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ISO/R 700 -1968 (E
2.3 Duty. A schedule of the loads on a machine or apparatus taking account of their respective
duration and sequence.
2.4 Periodic duty. A duty which is repeated periodically.
2.5 Duty cycle. The ratio of the duration of operation under load to the duration of the complete
cycle. This ratio, lying between O and 1, may be expressed as a percentage.
NOTES
1. The duty considered in this IS0 Recommendation is periodic duty comprising a certain period of
operation on constant load followed by a certain period of no-load operation; this represents the usual
conditions obtained during welding.
2. In English, the term “duty factor”, as used in the IS0 and IEC definitions, and the term “duty cycle”
are synonymous.
2.6 Conventional welding current. Current delivered by a welding machine on a practically non-
inductive resistance load.
2.7 Load voltage. The voltage between the output terminals of a welding machine, i.e. those to
which the electrode and return leads are connected, when a specified current is flowing through
a non-inductive resistance load.
2.8 Conventional load voltage. The voltage, at the output terminais of a welding machine, bearing a
linear relationship to the conventional welding current such that it is
20 volts at O ampere
44 volts at 600 amperes
i.e. such that the voltage is (20 * 0.04 Z) volts
where Z is the numerical value of conventional welding current in amperes.
For currents above 600 amperes, the voltage should remain constant at 44 volts.
2.9 Conventional operating welding conditions. Operating conditions defined by a conventional
welding current and the corresponding conventional load voltage.
2.10 Conventional welding duty. A periodic duty with a duty cycle of 0.6 comprising cycles of 5
minutes duration, a complete cycle consisting of a period of 3 minutes under the conventional
operating welding conditions followed by a period of 2 minutes of no-load operation.
2.1 1 Rated welding current. The maximum value of the conventional welding current at the conven-
tional load voltage at which the machine meets the requirements of this IS0 Recommendation
when operated at the conventional welding duty.
2.12 Rated short-circuit current. The current obtained at the maximum setting of the welding
apparatus when operating with a length of cable having a resistance as specified in Table 1 below,
the cross-sectional area of the cable being that used in welding practice for the rated current.
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ISO/R 700-1968 (E
TABLE 1 - Resistance corresponding to rated welding current
over up to and including
-
125 0.013
125 160 0.0070
160 200 0.0050
200 250 0.0040
250 315 0.0030
315 400 0.0020
0.0015
400 500
500 0.0012
630
NOTE. - Atolerance of 2 10 should be allowed on the values of resistance.
2.13 Rated maximum current. The maximum value of the current which can be obtained at the
conventional load voltage for the maximum setting.
2.14 Duty at rated maximum current. The periodic duty related to the rated maximum current which
corresponds to a duty cycle within the permitted heating limitations, and a cycle duration
which is the same as that for the conventional welding duty.
2.15 No-load voltage. The voltage between the output terminals of a welding machine when the
external circuit is open.
NOTE. - This definition applies generally where the welding machine is not fitted with a device for pro-
viding a lower open-circuit voltage. If the machine does have such a device, the no-load voltage defined above
appears at the output terminais immediately before the action of the time relays whose action is to effect a
reduction in the voltage when the welding circuit is open.
3. PRINCIPLE OF HEATING TESTS
The load should be a non-inductive resistance, and at a voltage equal to the appropriate conventional
load voltage. A tolerance of f 10 should be allowed on the value of the conventional load voltage.
Two tests should be made as follows
with rated welding current as defined in clause 2.1 1 and at the duty cycle of 0.6;
(a)
with the rated maximum current as defmed in clause 2.13 and at a duty cycle as defmed
(b)
in clause 2.14.
Test (b) may follow test (a) without the equipment returning to ambient temperature.
In the case of welding equipment with circuits which carry heavier current under no-load conditions,
an additional heating test should be carried out under no-load conditions and should immediately
follow test (a) or (b) without the equipment returning to ambient temperature.
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ISO/R 700-1968 (I
4. CONDITIONS UNDER WHICH TEMPERATURE
MEASUREMENTS ARE TO BE TAKEN
The temperature should be determined at the end of the first half of the last period of on-load
operation (see Fig. 1, point A).
FIG. 1 - Time-temperature curve.
This diagram is drawn for 60 duty cycle (X = 60)
5. LIMITS OF TEMPERATURE RISE
The limits of temperature rise for single operator natural, or forced air cooled or oil immersed arc
welding transformers, and for single operator arc welding generators measured under the conditions
specified in Part II, section 1, should be in accordance with the following :
5.1 Natural and forced air cooled arc welding transformers (see Table 2 below)
TABLE 2 - Limits of temperature rise*
Limits of temperature rise
Class of insulation
measured by thermometer measured by resistance
OC OC
A
65 60
E 80
75
B 90
80
F ** 115
1 O0
H ** 140 125
The values given in Table 2 comply with IEC Recommendations and may be modified should those Recom-
mendations be changed.
** The numerical values quoted for these classes of insulation should be considered as tentative only and may be
revised when more practical experience is available.
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ISO/R 700 -1968 (1
5.2 Oil immersed singie operator arc welding transformers
The temperature rise of all windings should be measured by change of resistance and should not
exceed 65 OC, and the temperature rise of the oil near the free surface should not exceed 55 OC.
Arc welding generators and associated electrical driving motors (see Table 3 below)
5.3
TABLE 3 - Limits of temperature rise*
Class of insulation A E B F** H**
- - - - -
R
T R R T R T R
OC OC OC OC OC OC OC
OC
- - - - - -
1.
(a) a.c. windings
(b) Field-windings of a.c.
and d.c. machines
having d.c. excitation 60 65 75 80 85 1 O0 105 125
other than those in
item 2
(c) Windings of armatures
having commutators
- - - - -
2.
Low resistance field-windings
1 O0 125
of one or more layers and 60 70 70 80 1 O0 125
compensating windings
-
3.
Iron core and other parts
75 95 110
in contact with windings
-
4.
Commutators and slip rings
80
70 80
open or enclosed
-
T = Temperature measurement by thermometer
R = Temperature measurement by resistance
The values given in Table 3 comply with IEC Recommendations and may be modified should those Recommen-
dations be changed.
** The numerical values quoted for these classes of insulation should be considered as tentative only and may be
revised when more practical experience is available.
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ISO/R 700-1968 (E
PART II
METHODS OF TESTS
1. DETERMINATION OF TEMPERATURE RISE
AND MEASUREMENT OF TEMPERATURE
The temperature rise of a part of a machine is the difference between the temperature of that part of
the machine and that of the cooling air, temperature being determined by one of the following
methods.
1.1 Thermometer method
In this method the temperature is measured by thermometers applied to accessible surfaces of
windings or other parts in accordance with the conditions stipulated below.
In measuring temperatures, thermocouples or resistance thermometers may be substituted for
thermometers provided that such instruments are inserted only in interstices accessible to the
bulb of a normal thermometer not less than 5 mm diameter.
1.2 Resistance method
In this method the temperature rise of windings is determined by increase in resistance. For
copper windings, the rise in temperature is obtained from the formula
t,+235 R
-=A
t1+235 R,
For practical purposes the following alternative formula may be found convenient in calculating
rise in temperature :
t, - fa =- R, -R, (235+ ri)+ (fi - fa)
Rl
where
is the temperature of the winding, in degrees Celsius, at the end of the test;
t,
is the temperature of the winding (cold) or at the moment of the initial resistance
I,
measurement, in degrees Celsius;
is the ambient air temperature, in degrees Celsius, at the end of the test;
ta
R is the initial resistance of the winding (cold);
is the resistance of the winding at the end of the test.
R,
The temperature rise should be measured as follows :
for windings, by means of the resistance method or, if this is not practicable, by means
of a thermometer placed at the hottest accessible spot on the surface of the winding;
- for other purrs, by means of a thermometer;
- for oil immersed equipment, by means of thermometers placed as near as possible to
the top level of the oil in the tank.
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ISO/R 700-1968 (E
It is not intended that measurement by both thermometer and resistance should be used and
one method only should be c
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