EN 60034-18-21:1994/A2:1996

SLOVENSKI STANDARD
01-april-1999
Rotating electrical machines - Part 18: Functional evaluation of insulation systems
- Section 21: Test procedures for wire-wound windings - Thermal evaluation and
classification (IEC 60034-18-21:1992/A2:1996)
Rotating electrical machines -- Part 18: Functional evaluation of insulation systems --
Section 21: Test procedures for wire-wound windings - Thermal evaluation and
classification
Drehende elektrische Maschinen -- Teil 18: Funktionelle Bewertung von Isoliersystemen
-- Hauptabschnitt 21: Prüfverfahren für Runddraht-Wicklungen - Thermische Bewertung
und Klassifizierung
Machines électriques tournantes -- Partie 18: Evaluation fonctionnelle des systèmes
d'isolation -- Section 21: Procédures d'essai pour enroulements à fils - Evaluation
thermique et classification
Ta slovenski standard je istoveten z: EN 60034-18-21:1994/A2:1996
ICS:
29.080.30 Izolacijski sistemi Insulation systems
29.160.01 Rotacijski stroji na splošno Rotating machinery in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME
CEI
INTERNATIONALE
IEC
34-18-21
INTERNATIONAL
STANDARD
AMENDEMENT 2
AMENDMENT 2
1996-11
Amendement 2
Machines électriques tournantes –
Partie 18:
Evaluation fonctionnelle des systèmes d'isolation –
Section 21: Procédures d'essai pour enroulements
à fils – Evaluation thermique et classification
Amendment 2
Rotating electrical machines –
Part 18:
Functional evaluation of insulation systems –
Section 21: Test procedures for wire-wound
windings – Thermal evaluation and classification
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34-18-21 Amend. 2  IEC:1996 – 3 –
FOREWORD
This amendment has been prepared by subcommittee 2J: Classification of insulation systems
for rotating machinery, of IEC technical committee 2: Rotating machinery.
The text of this amendment is based on the following documents:
FDIS Report on voting
2J/51/FDIS 2J/58/RVD
Full information on the voting for the approval of this amendment can be found in the report on
voting indicated in the above table.
___________
Page 13
3.4.1  Construction of test objects
Replace the text of the note by the following:
NOTE – It is recognized that markedly different values of test life can be obtained for the same insulating
materials, depending on insulation thicknesses and creepage distances.
Page 15
3.7  Ageing temperature and subcycle lengths
Replace the fourth paragraph by the following:
Ageing temperatures and lengths of ageing subcycles should be selected from table 2 of
Section 1.
Replace, on page 17, the seventh paragraph by the following:
In addition, at least two higher ageing temperatures should be selected, separated by intervals
of 20 K or more. Intervals of 10 K may be used when tests are made at more than three ageing
temperatures.
Page 17
4.1.1  Procedure 1
Replace the existing text by the following:
This procedure, using "motorette" type models as test objects, shall be referred to as IEC 34-18-21,
Procedure 1.
34-18-21 Amend. 2  IEC:1996 – 5 –
Page 23
5.1.1  Procedure 2
Replace the existing text by the following:
This procedure, using actual motors as test objects, shall be referred to as IEC 34-18-21,
Procedure 2.
5.1.2  General features
Replace the fourth paragraph by the following:
Even though actual motors are tested, the results may not be used to determine endurance
time in actual service in an absolute sense. The tests may be used as a means of classification
only by comparing insulation systems.
Page 25
5.3.2  Means of heating
Replace the first paragraph by the following:
The mode of heat generation is dictated by the type of motor being used in the test and the
laboratory equipment available. Higher than normal winding temperatures can be obtained by
increasing motor losses by such means as enlarging the air gap, starting and reversing each
motor, superimposition of direct current on the normal alternating current, or by increasing the
temperature of the air surrounding the motor. For temperature regulation during the heat
ageing portion of the cycle, the motors may be run at normal voltage and frequency with an
electrical control which automatically starts and stops or reverses the direction of rotation of
the motors at intervals. Other acceptable means of temperature control include automatic
voltage variation, adjustment of the surrounding air temperature, or combinations thereof.
Replace the third paragraph by the following:
Single-phase motors shall have at least 250 start-stop operations each day of the heat ageing
portion of the cycle. The starting winding of a single-phase motor normally operates at a much
higher current density than the main winding during starting. During each start it can reach a
temperature of 10 K to 30 K higher than the main winding. In order to ensure that the correct
emphasis is placed on the main winding portion of the insulation system, a reasonable number
of starts should be employed.
Replace, on page 27, the fourth paragraph by the following:
Polyphase motors shall have at least 1000 starts or reversals each day of the heat ageing
portion of the cycle. Often the electrical loss during reversal is used to maintain the elevated
temperatures, in which case the number of reversals may greatly exceed 1000 per day. At the
highest temperature test the total time of exposure is relatively short which results in a
relatively low number of reversals during the life of the test. At the lowest temperature, the time
of exposure can be 16 to 20 times as long as that of the highest level. A wide variation in total
number of starts would affect the slope of the time-temperature curve within a cycle. Thus, it is
recommended that the number of reversals at the low temperature be no greater than twice
those at the high temperature. Ideally, an equal number of reversals at each temperature
should be sought.
34-18-21 Amend. 2  IEC:1996 – 7 –
5.3.4  Mechanical stresses during the thermal ageing subcycle
Replace the first paragraph by the following:
Mechanical stress is obtained in tests on actual motors by the normal vibration of the motor
running and with starts or reversals, or both. There is mechanical shock from starting or
reversing. The vibration amplitude at twice the line frequency can be increased by enlarging the
air gap. Larger forces are present in the windings as a result of the high currents during
starting and reversing of the motors. In a test, these mechanical forces occur at elevated
temperatures.
5.4.1  Moisture test
Replace the first paragraph by the following:
A moisture test of at least 48 h shall be used, except that for totally enclosed machines
(degrees of protection IP44 or more) and for d.c. machines a moisture test is not mandatory
because it can be impracticable. Mo
...