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UDC 621.791.76
IS0
I NT ERN AT1 O N A L O RG A N IZATl ON FOR STA N DARD IZATION
IS0 RECOMMENDATION
R 669
RATING OF RESISTANCE WELDING EQUIPMENT
1st EDITION
February 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 only
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 669, Rating of resistance welding equipment, was drawn up by
Technical Committee ISO/TC 44, Welding, the Secretariat of which is held by the Association Fran-
çaise de Normalisation (AFNOR).
Work on this question by the Technical Committee began in 1957 and led, in 1963, to the
adoption of a Draft IS0 Recommendation.
In May 1966, this Draft IS0 Recommendation (No. 974) 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
Israel Switzerland
Belgium
Japan Turkey
Brazil
Chile Korea, Rep. of U.A.R.
Czechoslovakia Norway United Kingdom
Denmark Poland Yugoslavia
Romania
Finland
France South Africa,
Germany Rep. of
Hungary Spain
Six Member Bodies opposed the approval of the Draft :
Canada
India
Netherlands
Portugal
U.S.A.
U.S.S.R.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
which decided, in February 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 669 -1968 (E
IS0 Recommendation R 669 February 1968
RATING OF RESISTANCE WELDING EQUIPMENT
PART I
GENERAL
1. SCOPE
This IS0 Recommendation applies to single-phase resistance welding machines, including complete
mobile equipment, but not to transformers supplied separately. Provisionally, it covers equipment
whose maximum conventional power (see clause 2.8) does not exceed 400 kVA.
It applies to equipment for use under the following conditions :
Altitude. In the absence of any information concerning height above sea level at which
(a)
the machine 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,
it is assumed that, for water-cooled machines, the temperature of the cooling water does
not exceed 25 “C at the inlet of the machine and, in the case of air-cooled machines, that
none of the following limits is exceeded :
- maximum ambient air temperature 40 “C
~ daily average ambient air temperature 30 “C
-- yearly average ambient air temperature 20 “C
Pressure of cooling water. In the absence of any information to the contrary, it is assumed
(c)
that the pressure of the cooling water is not less than that for which the machine is
designed.
2. DEFINITIONS
2.1 Operating conditions. All quantities defining the performance of a machine.
2.2 Rated. Qualifying term applied to a quantity which is used in the specification of resistance
welding equipment.
Duty. A schedule of the loads on an apparatus or machine taking account of their respective
2.3
duration and sequence.
2.4 Periodic duty. A duty which is repeated periodically.
Duty cycle (see Note 1). The ratio of the duration of the electrical load (see Note 2) to the
2.5
duration of the complete cycle. This ratio, lying between O and 1, ‘may. be expressed as a per-
centage.
NOTES
1. In English, the term “duty factor”, as used in the IS0 and IEC definitions, and the term “duty cycle” are
synonymous.
2. In this IS0 Recommendation, the word “load” should be considered in a restricted manner. It refers to a con-
stant load which excludes all periods of pre-heat, post-heat and slope control.
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ISO/R 669 -1968 (E)
2.6 Maximum short-circuit power (P,). The maximum apparent power at the terminals of the
machine, expressed in kilovolt-amperes, absorbed at the highest regulator setting, the electrodes
being short-circuited according to conditions laid down in the methods of test (see Part II,
section 1) and the machine arranged in such a manner as to have the minimum secondary
impedance compatible with this method of short-circuit.
Maximum welding power.* The power equal to 0.8 of the value of maximum short-circuit
2.7
power.
2.8 Maximum conventional power at 50 "Io duty cycle (Pc).* The maximum apparent power,
expressed in kilovolt-amperes, corresponding to an actual or assumed continuous service at a
duty cycle of 50 "Io with the regulator at its highest setting without exceeding the temperature
rises specified in section 4, when tested in accordance with the following recommendations.
3. CONDITIONS UNDER WHICH TEMPERATURE MEASUREMENTS SHOULD BE TAKEN
3.1 Air-cooled transformers
The test should be made at an ambient air temperature of at least + 10 OC. It is assumed that
the rise in temperature is the same for ambient temperatures between + 10°C and +40 "C. The
ambient temperature should be taken as the average registered during the last quarter of the test.
The rises in temperature should be measured by either the resistance or thermometer method
in the case of primary windings, and by either thermometer or embedded detectors in the case
of secondary windings, provided that, when using the thermometer method, the measurement is
taken at the hottest accessible point.
The temperature rise should be measured immediately after the end of the last period under
load.
The highest temperatures registered should be the reported values.
3.2 Water-cooled transformers
In determining the temperature rises, account should be taken of the actual water inlet tempera-
ture at the time of the test.
The water inlet temperature should be taken as the average registered during the last quarter of
the test.
The temperature rise should be measured by either the resistance or embedded detector method
in the case of primary windings, and by either the thermometer or embedded detector method
in the case of secondary windings.
When using the resistance method the temperature should be measured with the cooling water
shut off and the load removed. The readings should be taken not less than 15 seconds and not
more than 60 seconds after shutdown.
When using the embedded detector method for measuring the temperature of either the primary
or the secondary windings, and the thermometer method for measuring that of the secondary
windings, the temperature should be measured with the cooling water flowing and the load
applied.
The highest temperatures attained should be the reported values.
See Part 111. The maximum welding power is symbolized by Smax. The maximum conventional power at 50 oh
duty cycle is symbolized by Sconv.
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ISO/R 669 -1968 (E
4. LIMITS OF TEMPERATURE RISE
The limits of rise in temperature for air-cooled and water-cooled transformers should be in accordance
with the following Table.
TABLE - Limits of temperature rise*
Method of Limits of temperature rise, in OC,
Cooling
for classes of insulation
Winding determination
medium
H**
A E B F**
Resistance
60 75 85 105 130
Primary -
Thermometer
55 70 80 1 O0 120
c
Thermometer 55 70 80 1 O0 120
Secondarv I I I I I
I ’
Embedded
65 80 90 115 140
detector
Resistance
70 85 95
115 140
Primary ***
Embedded
75 90 1 O0 125 150
detector
WATER
Thermometer 65 80 90 110 135
-
Secondary
Embedded
75 90 1 O0 125 150
detector
L
*
The values given in this Table are in accordance with the Recommendations of the International Electro-
technical Commission and may be modified when those Recommendations have been modified.
**
The numerical values quoted for classes F and H should be considered as tentative only and may be revised
when more practical experience is available.
*-
***
These maximum rises in temperature for primary windings apply only where there is intimate contact between
these windings and the parts directly cooled by water.
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ISO/R 669 -1968 (E
PART II
METHODS OF TEST
1. DETERMINATION OF MAXIMUM SHORT-CIRCUIT POWER (Pm)
1.1 General
The resistance welding machine should be brand-new. In determining the maximum short-
circuit power, the rated primary voltage of the machine should be used. The supply voltage
under load, measured at the terminals of the machine, should not differ by more than+ 5 and
-10 from the rated voltage. Corrections should be made by the rule of proportionality of the
current to the voltage.
1.2 Conditions of short-circuit
1.2.1 Spot and seam welding machines. The short-circuit should be effected by bringing together
the electrodes, having regard to the following condition :
d = (0.5 ? O.OS)G> 2.5
where
d is the diameter of the tip of the electrode or the width of the tread of the wheel,
expressed in mil
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