REDESIGNING THE COIL END INSU- LATION OF ELECTRICAL MOTOR Joonas Kauppinen

REDESIGNING THE COIL END INSU- LATION OF ELECTRICAL MOTOR Joonas Kauppinen
Joonas Kauppinen
REDESIGNING THE COIL END INSULATION OF ELECTRICAL MOTOR
Technology and Communication
2014
VAASAN AMMATTIKORKEAKOULU
Kone- ja Tuotantotekniikan koulutusohjelma
TIIVISTELMÄ
Tekijä
Opinnäytetyön nimi
Vuosi
Kieli
Sivumäärä
Ohjaaja
Joonas Kauppinen
Redesigning the Coil End Insulation of Electrical Motor
2014
Englanti
44
Mika Billing
Tutkimus tehtiin ABB Motors & Generators Vaasan yksikölle. Tutkimus pohjautuu kesällä 2013 tapahtuneeseen koneiden yllättävään hajoamiseen. Tutkimuksessa todettiin eristeiden tarvitsevan uutta suunnittelua.
Tutkimus suoritettiin tutkimalla eristeille vaadittavia ominaisuuksia. Eristeille tehtiin testejä ja parhaista vaihtoehdoista tehtiin prototyyppi, jolloin uusia eristyksiä
pystyttiin vertailemaan vanhaan eristykseen.
Tutkimuksissa todettiin, että alkuperäinen eristeryhmä oli aivan liian paksu ja
sähköiset ominaisuudet ylittivät vaaditun rajan. Eristeisiin tehtiin optimointia ja
materiaalimuutoksia.
Avainsanat
eristys, tuotekehitys, sähkömoottori
VAASAN AMMATTIKORKEAKOULU
UNIVERSITY OF APPLIED SCIENCES
Kone- ja Tuotantotekniikka
ABSTRACT
Author
Title
Year
Language
Pages
Name of Supervisor
Joonas Kauppinen
Redesigning the Coil End insulation of Electrical Motor
2014
English
44
Mika Billing
The thesis was made for ABB Motors & Generators in Vaasa. The thesis is based
on a case in June 2013 when a few same type of electric motors suddenly broke
down. In the investigations it was noticed that the insulations in the electric motor
need to be redesigned.
The thesis was made by searching the old and the new insulations properties. Different tests were conducted to the insulations and prototypes were manufactured
of the best ones.
The thesis shows that the old insulations were too thick and the electrical properties were much higher than the limit. The impregnation level insulations was decreased because of multilayer insulation.
Keywords
Insulation, product development, electric motor
TABLE OF CONTENTS
ABSTRACT
1 INTRODUCTION ............................................................................................... 2
2 ABB OY, INTRODUCTION .............................................................................. 3
3 ELECTRIC MOTORS ......................................................................................... 4
4 STATOR PRODUCTION AND WINDING STYLES ....................................... 6
4.1 Overlap Winding ........................................................................................ 8
4.2 Cross Winding ............................................................................................ 9
4.3 Concentric Winding.................................................................................. 10
5 STATOR INSULATION AND TESTING ........................................................ 12
5.1 Required Properties of Insulation ............................................................. 12
5.2 Insulations Testing.................................................................................... 13
5.3 Resin. ........................................................................................................ 17
6 PROBLEMS ....................................................................................................... 24
7 INVESTIGATING SOLUTIONS ...................................................................... 28
8 SOLUTION ........................................................................................................ 42
8.1 Insulation .................................................................................................. 42
8.2 Impregnation level .................................................................................... 42
8.3 Cost comparison ....................................................................................... 42
9 THE CONCLUSION OF THE WORK ............................................................. 43
SOURCES ............................................................................................................. 44
TABLE OF FIGURES
Figure 1. The cross section of the Electric motor ................................................... 5
Figure 2. Stator core ready for winding. ................................................................. 6
Figure 3. The end coil tied with lacing. .................................................................. 7
Figure 4. Double label overlap winding. ................................................................. 9
Figure 5. 8-pole cross winding. ............................................................................. 10
Figure 6. 4-Pole concentric winding. .................................................................... 11
Figure 7. Thermal class figure .............................................................................. 13
Figure 8. Thickness measurement ......................................................................... 14
Figureure 9. Apparatus of electrical strength test ................................................. 15
Figure 10. Apparatus of elongation test ................................................................ 16
Figure 11. Insulation hammer test. ........................................................................ 17
Figure 12. Minimum and maximum values of polyester resin viscosity as a
function of a temperature. ..................................................................................... 19
Figure 13. Minimum and maximum values of epoxy resin viscosity as a function
of a temperature..................................................................................................... 20
Figure 14. Table of trickle impregnations temperature phases ............................. 21
Figure 15. Tool for archiving measurement result ................................................ 22
Figure 16. Impregnated stator. .............................................................................. 23
Figure 17. Air pockets in end coil. ........................................................................ 25
Figure 18. Dry spot in coil .................................................................................... 25
Figure 19. Dry spot after removing the insulation ................................................ 26
Figure 20. The correct phase insulation in slot. .................................................... 26
Figure 21. Slot insulation failure. .......................................................................... 27
Figture 22. Insulation group AOMF+APGNH+AOMF ....................................... 36
Figure 23. Insulation group AOMF+APGNH after hammer test ......................... 37
Figure 24. Hammer test result of APGNW ........................................................... 38
Figure 25. Rupture in NMiN+APGNF ................................................................. 39
Figure 26. Rupture in APGNW ............................................................................. 39
Figure 27. Impregnation level in old H-class VSD motors................................... 41
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Electric motor = Converts electrical energy to mechanical energy
Stator = Electric motors solid part which produces magnet field to rotate rotor
Coil = Copper thread is placed inside of the stator in a way that when electricity is
fed to them, they produce magnetic field.
Insulation = Substance which insulate electricity.
Resin = Substance that is used in stators impregnation. Increase the properties of
insulation system.
VPI = Vacuum pressure impregnation.
VSD = Variable speed drive. Frequence converter drive motor.(Multi-speed)
NEMA= National Electrical Manufactures Associative
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1 INTRODUCTION
The subject of the thesis was redesigning the insulation of VSD motors H-class.
The insulation in the electric motor is one of the most important structures in the
electric motor. The insulation is the substance that separates phases from each
other’s. Motors that run in different temperatures have their own insulation classes. The H-class insulation must withstand the temperature of 180 Celsius degrees.
This thesis was made for ABB Motors & Generators Vaasa. The objective of the
thesis was to redesign the H-class stators in VSD motors. The object of the redesigning was to create a new insulation group that impregnates better. The redesigning includes the investigation of the old and the new insulations and creating a
new insulation group for stator. The thesis also deals with the investigation of resins properties and different ways to impregnate the stator.
The goal of thesis was to increase the impregnation level of the stators. By increasing the impregnation level the lifetime of the motors was also increased.
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2 ABB OY, INTRODUCTION
ABB Oy is one of the leading electrical and automation technology companies,
founded in 1988. ABB was founded when Swedish Asea and Swiss Brown Bover
merged. The ABB name comes directly from the initials of Asea and Brown Bover. ABB has got approximately 150 000 employees in 100 different countries. In
Finland ABB has 6600 employees. ABB’s major factories in Finland are located
in Vaasa and in Helsinki. ABB has also few minor maintenance and product development units all around Finland. /1/
ABB Finland’s turnover in 2012 was 2.4 billion euros. According to ABB’s president Tauno Heinola, ABB is building the future by investing strongly in the product research and development. In 2012 ABB pronounced spending 184 milion euros on the product development which is 7,4 percent of the turnover. ABB’s turnover in total in 2012 was 39,336 billion US dollars which is approximately 28, 66
billion euro’s. /2/, /3/
ABB Motors and Generators Vaasa produce electric motors and generators. The
Vaasa’s unit is specialized in producing explosion safe low voltage motors but
also producing other specialized motors.
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3 ELECTRIC MOTORS
Electric motors convert electrical energy to mechanical energy. For this conversion the electric motor uses electrical magnetic field. Electricity is fed to a copper
coil which produces magnetic field. Inside the motor a rotor is magnetised. Because of the rotors magnetic field the rotor revolves to the same position with stators magnet field. By feeding electricity to differed coils the rotor starts to revolve. If there is need to convert mechanical energy to electrical energy it is also
possible. These machines are called generators. Generators work just the opposite
than motors. When the magnetised rotor is revolving it inducts electricity to coils
by changing the magnetic field. /9/
There are many varieties of electric motors. Electric motors can be built for alternating current or to direct current. Direct current motors are used for example in
battery used power tools like electric screwdrivers. Usually alternative current
motors are more powerful than direct current motors. Alternative current motors
are used in factories for many purposes. /9/
The main components of an electric motor are the stator and the rotor. The electric
motor also includes a frame. The structure of the electric motor has been developing since 1740. The first electric motor which contained the stator and rotor was
developed in 1832. A picture of an electric motor with components is presented in
figure 1.
The stator core is compressed of several electrical plates. Each electrical plate has
got slots for coils which are made by using the punch. The stator is wound, insulated and impregnated before the stator is compress fitted inside to the frame.
The core of the rotor is compressed of electrical plates. Also in every electrical
plates there is a slot for rotor poles. Rotor pole are manufactured of melted aluminium. To the both end of the poles a short circuit ring is attached. The shaft is
attached inside of the rotor to convey the energy to mechanical. At the end of the
shaft there is a cooler fan which revolves by the power of the motor and helps the
motor to cool down.
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The frame is the outer part of the motor. The frame positions every other part to
their right positions by using compress fit and bearings. The stator is compress
fitted to the frame and rotor lies on frames bearings. The surface of the frame is
usually made wing shaped. This form conducts heat out of the motor easier. The
connection box is also a part of frame. The electricity is fed through the connection box to the stator. The connection box includes connections for several attachments. Every motor has got a rating plate, which shows the model and other
information of the specific motor. The rating plate is also a part of the frame.
Figure 1. The cross section of the Electric motor
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4 STATOR PRODUCTION AND WINDING STYLES
The manufacturing of the stator begins from the stator core. The stator core is
piled of electric plates and compressed together. When the plates are compressed,
finger plates are attached to the core. The finger plates keep plates tightly compressed. The winding begins, after the stator core is ready, as shown in figure 2.
Figure 2. Stator core ready for winding.
The winding begins with placing the slot insulation. The slot insulation prevents
ground contacts and protects copper coils from mechanical stress. After placing
the slot insulation copper coils will be added to the slots. The coils are in groups
and can be placed in different ways in to the slots. Depending on the winding
style, the position of coils changes. While the coils are placed to the slots the ends
of coils are shaped at the same time. They must be shaped in the way that the coils
cannot touch the rotor, frame or end shield. If the end coils touch the end shield or
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the frame, it creates a short circuit or ground contact. That is why they have a
shape tolerance. The ends of coils must be insulated at least from phase to phase.
Different phases cannot touch each other because it will cause short a circuit and
burning of the motor. When the coil insulation is placed, the ends of coils are tied
with lacing and simultaneously coils are hammered so that the lacing will be tight.
This ensures that the insulations will stay in place and copper wires stay close to
each other, as shown in figure 3. /8/
Figure 3. The end coil tied with lacing.
Finally the stator is impregnated with resin. The impregnation depends on the size
and the insulation level that is required. It can be trickle, dip or vacuum impregnated, the resin can be polyester or epoxy.
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4.1 Overlap Winding
In overlap winding all copper coils run to the same direction. The winding has
been made as double level overlap winding, as seen in figure 2. The outer coils go
to one direction and the inner coils go to the other. The overlap winding has regular torque because it has regular wounds. Normally the overlap windings are used
with a frequency converter. With the frequency converter the frequency that is fed
to the motor can be modified. This affects the rotation speed of the rotor and this
enables adjusting the revolving of the motor in variable speeds.
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Figure 4. Double label overlap winding.
4.2 Cross Winding
In cross winding the copper coils are placed to go across each other, as shown in
figure 3. Cross winding motors do not have as regular torque than overlap winding but cross winding is much easier and faster to manufacture.
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Figure 5. 8-pole cross winding.
4.3 Concentric Winding
The advantage of concentric winding is that the voltage between the phases is
lower. This enables using less electric insulation than in other winding styles. The
problem in concentric winding is that concentric winding can’t be done to bigger
motor sizes. Concentric winding is suitable for 355 and smaller motors. Some of
the concentric windings can be wound with machines which makes winding easier
and faster.
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Figure 6. 4-Pole concentric winding.
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5 STATOR INSULATION AND TESTING
The purpose of the insulation in electric motor is to insulate electric phases from
each other and from the stator core. In the case of an insulation failure the electric
motor goes to short circuit which might lead the motor to burn. In the end coils,
the insulations are strips which are placed between phases or between the coil
groups. To get the insulation to stay in the right place, the stator is impregnated
with resin. Electric motors have two different insulation groups, phase insulation
and slot insulation. The phase insulations are in end coils and slot insulations are
in the slots. /13/
5.1 Required Properties of Insulation
The insulations must withstand several different stresses such as mechanical, high
temperatures, temperature changes and electrical stress. The insulations must
stand the winding process where it gets twisted and hammered with a rubber
hammer. In the final wiring the insulations usually bend tightly which might tear
the insulation. The most important property of the insulation is electrical insulation. Insulation must be chosen depending on the motor properties. /10/
Electric motors have different classes for different running temperature. NEMA
has defined temperature classes such as B-class, F-class and H-class. The F-class
must stand 155 C and H-class 180 C. The thermal class consist of the maximum
ambient temperature, the rise of permissible temperature and the hotspot margin.
ABB uses the F-class insulation when making a B-class motor. This gives longer
life to motor insulation and a much higher marginal. The temperature class affects
always when choosing insulation for the stator. If temperatures are higher the insulation in the stator must have better properties. Usually when higher temperatures and partial discharge resistance are required, the mica is used in insulation.
/4/
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Figure 7. Thermal class figure
The difference in insulation between the VSD-motor and the DOL-motor is that
the VSD-motor needs insulation that can stand higher electrical stress. In VSDmotors the fed voltage may change much more than in DOL-motors, because of
the frequency converter. For example if in VSD-motors the rated voltage is 500
V, the highest voltage spike may be 1,3 kV. If the insulations breakdown voltage
in VSD-motor is not high enough, the motor will go into short circuit. ABB informs that if the rated voltage of the VSD-motors is under 600 V, special insulation is not necessarily needed. In DOL-motors the voltage remains stable and that
is why DOL-motors are produced with non-mica materials. /5/
5.2 Insulations Testing
To ensure the quality of the insulations the insulation must be tested. To test the
insulation there are many different methods, such as thickness, electrical strength
test, grammage measurement, elongation test, loss of mass test and hammer test.
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If the insulation is not as thick as it should be, its electrical strength is not as good
as is stated. The test is made by using a micrometre. In the test several measurements must be taken in different places around the insulation piece, picture 6.
Every insulation has its own tolerance, how thin or thick the insulation can be.
/12/
Figure 8. Thickness measurement
In the electrical strength test the insulation is set between electrodes. Electrodes
are charged and voltage raised to 500 Volts per second. When the voltage is high
enough the insulation will break down and lets the current go through. This information helps to know which insulation has enough electrical strenght for different motor types. Electrical stress test is also made to insulations which are impregnated. When the insulation is impregnated its electrical properties usually get
better, but it will be tested to be sure of the breakdown voltage in the manufactured motor. /12/
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Figureure 9. Apparatus of electrical strength test
In the grammage test the test pieces are of equal sizes. First the insulations are cut
into pieces. Then the insulations are placed to oven in 105 C for 30 to 60 minutes
depending on the size of the test pieces. The test piece is put to oven to decrease
the moisture of the test piece. After oven the insulations are weighed and calculated how much insulation weighs per square meter. /12/
In the elongation test the test piece is attached to a clamping device which extends
the insulation. The distance between the clamps must be 200 mm. The test continues until the test piece ruptures. The results of the extensions are reported. /12/
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Figure 10. Apparatus of elongation test
In the loss of mass test the preferred size of the piece is 100x25 mm. Test pieces
are weighed with a highly sensitive scale which detects the change of mass in 0,2
% units. The test pieces are placed into the oven in different temperatures for a
certain duration. The test pieces are in the oven for example in 140 C for 14 days.
The loss of mass is calculated. /12/
One way to test mechanical stress endurance is the hammer test. In the hammer
test the insulation is placed in side of the coil and the insulation is turned into a
tight corner. After placing the insulation inside of the coil, the coil is beaten with
rubber hammer for ten times, as shown in figure 11. After hammering the insulation piece is removed of the coil. The test piece is checked if there are any cracks.
The test simulates the mechanical stress in a real winding situation. This test helps
to make sure that insulation can stand the winding process. /12/
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Figure 11. Insulation hammer test.
5.3 Resin
The purpose of the resin in the stator is to fill all air pockets in coils and impregnate the insulation. When the insulation is impregnated with resin, the breakdown
voltage strength of the insulation material increases, as shown in Table 1. Resin
also act as insulation in coils. If the impregnation fails and air pockets remain in
coil, it may lead to a partial discharge and the motor to lose power and length of
age. If the impregnation is well made, resin forms a thermal conductor and solid
structure which prevents tremble when the motor is running. /11/
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Table 1. Average of breakdown voltages
Unimpregnated, aged
in oven for 4 hours in
Polyester resin
epoxy resin
160 °C
aver-
aver-
aver-
er-
stde std
kV
er-
stde std
kV
er-
stde std
kV
age
v
ev
/m
age
v
ev
/m
age
v
ev
/m
[kV]
[kV]
[%]
m
[kV]
[kV]
[%]
m
[kV]
[kV]
[%]
m
AO
M
F
15. 11.
1.3
0.2
6%
5
7.7 44.
11.6
0.9
%
1
27. 31.
8.8
2.5
9%
5
AP
GN
H
5.8 24.
4.4
0.3
%
5
1.7 20.
5.9
0.1
%
8
22. 15.
4.4
1.0
4%
1
Resins can be single or multi-component resins. This means how many different
substances are blended before the resin is able to react. If the resin is singlecomponent it does not need any other substance to react. Multi-component resins
need one or more substances to start reacting. Viscosity is very important measurement in resins and it may vary in resins. Viscosity is a detector of ageing, mixing ration and reacting. If the resin has started to react and the mixing ratio is right
the viscosity is much higher than normally.
Viscosity is the inner friction of substances. Friction is measured with a Din-cup.
The Din-cup is a cup that has got a small hole on the bottom. Viscosity can be
calculated from the time that resin takes when it runs through the cup. Temperature has a major impact to viscosity. As can be seen in figures 12 and 13, if the
temperature is high, the viscosity is low and if the temperature is low, the viscosi-
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ty is high. To ensure that the resin is good, the results must be compared to result
shown in picture. If the time and temperatures result is between maximum and
minimum lines it means that the viscosity is correct. /6/
Figure 12. Minimum and maximum values of polyester resin viscosity as a function of a temperature.
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Figure 13. Minimum and maximum values of epoxy resin viscosity as a function
of a temperature.
Resin components can be harmful to human health. This is the main reason why
protection gear must be worn while handling resin. When the resin has hardened it
is not so dangerous to human or nature anymore. /6/
Stators can be impregnated with a few different techniques. ABB Vaasa factory
uses vacuum pressure impregnation (VPI) and trickle impregnation. The trickle
impregnation is used at ABB for bigger stator sizes and vacuum impregnation for
smaller sizes. /6/
At the moment ABB uses three different resin types. Double-componential polyester resin and double-componential epoxy resin are used in trickle impregnation.
In the vacuum impregnation single componential polyester resin is used. /6/
In trickle impregnation stators coils are heated to the starting temperature which
decreases the viscosity of the resin. This ensures that the resin spreads more easily
to everywhere in the stator. When the resin is all over coils and inside of the slots,
resin gelling begins. When the temperature is raised to around 95-125 C, the resin starts to react and it starts to turn from liquid to solid. The gelling temperature
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depends on the resin. Usually polyester resin starts to react at about 90 C and
epoxy at about 125 C. At the end the resin is hardened in a higher temperature.
Similar to gelling temperatures also hardening temperatures depend on the resin.
Usually the temperatures are around 135-160 C. Finally the stator is put into the
oven for a few hours in 160 C. The impregnation phases can be seen in figure 14.
/6/
Figure 14. Table of trickle impregnations temperature phases
In the vacuum impregnation the stator is placed into a tank. When the stator is in
the tank, a vacuum is created into the tank. This way there cannot remain any air
pockets inside the stator. After the tank is totally vacuumed the resin is released
and it runs all over the stator including inside the stator. If the vacuum is not
properly maid, air pocket remains inside of the stator and the resin cannot invade
properly. /7/
According to ABB’s precept it would be good if resin - copper ratio is 9 %. To
ensure this, the stator is weighed before the impregnation and after the impregnation. The start weight and the end weights are fed into the system, which registers
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the weights, the specific stator and the model. The system tells how much resin
remained inside the stator. The measurement tool can be seen in Figure 15. In the
long run it is good to see how impregnation quality develop has gone. If the resin
to copper ratio starts to drop, it can be investigated. Without the system no one
knows if there is a problem. Now ABB can also tell the client how much resin
their motor contains. /6/
Figure 15. Tool for archiving measurement result
Polyester resin is mainly used in the vacuum impregnation because it has got low
viscosity without heating. This helps the resin to penetrate inside of coils and into
the slots. Polyester resin in the vacuum impregnation is mainly singlecomponential resin. Polyester resin is also used in the trickle impregnation in single- and multi-componential.
The viscosity of epoxy resins is a bit higher than that of polyester resin. After
heating epoxy resin its viscosity turns very low and the resin gets very liquid. That
is why epoxy needs a high temperature to jellify. When epoxy resin is hardened, it
withstands high temperatures easily. Impregnated stator shown in figure 16.
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Figure 16. Impregnated stator.
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6 PROBLEMS
Main problem is that the stators have too much insulation. It leads to that resin
cannot spread all over the stator coils, which means that air pockets remain in
coils, which might result in partial discharge. One target stator has got the H-class
VSD structure and in the end coils two different insulation groups are used. Coils
are insulated with three insulation stripes which are PET-fleece (AOMF 0.15),
glass-mica laminate (APGNH 0.18) and PET-fleece (AOMF 0.15). The phases are
insulated with four insulation stripes which are PET-fleece (AOMF 0.15), glassmica laminate (APGNH 0.18), mica-insulation (APGNH 0.18), PET-fleece
(AOMF 0.15). APGNH contains mica in silicone which has got great short circuit
resistance. The PET-fleece is papery insulation that protects mica-insulation from
mechanical stress and impregnates with resin extremely well.
At the moment the target stator is impregnated with double-componential epoxy
resin. The impregnation is performed in accordance with ABB instruction Fimot
0249. After the impregnation the stator is put into oven in 160 C for two hours.
As an example ABB produced a stator which was a H class VSD structure motor.
The stator did not have resin enough to fill all the air pockets and resin did not
penetrate all over coils, as can be seen in figure 13. The stator had enough insulation but not enough resin. Several dry spots were found from the stators insulation. These dry spots are a bad sign of the quality of the impregnations.
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Figure 17. Air pockets in end coil.
Figure 18. Dry spot in coil
Dry spots are seen as light areas in the insulations which can be seen in figure 17.
The insulation on top was removed to see how coils were impregnated as can be
seen in figure 18. The result was extremely bad, copper wires were loose from
each other because there was not any resin to bind the copper wires together. In
these cases copper wires were exposed to tremble which can cause in the long run
copper wires abrasion and it causes partial-discharges or severance of the copper
wires.
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Figure 19. Dry spot after removing the insulation
The main reason for the motors failure was the phase insulation in slot. The insulation group were NKN2525 and two APGNH, as can be seen in figure 20.
Figure 20. The correct phase insulation in slot.
In large motors the phase insulation in slot is very long and it easily turns away
from the middle of the phases, where it should be, as shown in figure 21. The
flabbiness of the APGNH is the main reason why insulation was not in the correct
position. When watching the phase insulation in slot from the end coil, it seems to
be in the correct position, but in the middle of slot the insulation might not be in
the correct position. When the phase insulation in slot was not between the phases
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the motor was in short circuit which resulted the motor to burn, figure 21. In the
picture it can be seen how the phase insulation turns away from the middle of the
phases.
Figure 21. Slot insulation failure.
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7 INVESTIGATING SOLUTIONS
The three biggest insulation manufacturers that produce insulation for ABB were
investigated for new insulation solution. At the beginning all the required properties were listed with the help of ABB’s database and the insulation team so that
requires were easy to recognise. First thing required from the insulation group was
that it must contain mica bonded with silicone and it also must contain some kind
of insulation that increases the mechanical strength of the mica insulation. Electrical breakdown must withstand over 10 kV. In the insulation group the F-class insulation can be used if the insulation is used with the H-class insulation.
From every of the three biggest insulation manufacturers data sheets were
searched that meets all the requirements. When searching for the optimal insulation for the stator, only few were found. Most of the insulations were good for slot
insulation. Sample pieces of insulation were ordered for tests.
The combinations of insulations were made, with help of the ABB’s insulation
team. For replacing the old insulation, a few new insulation groups were designed,
as can be seen below, in table 3 and table 4. In the tables the differences of the
new and the old insulations are compared. Every insulator has own task when insulating the stator. Some insulation protects motor from partial discharge and others from breakdown. Mica gives the content to the insulations, which protect the
motor from a partial discharge. Thickness has also an impact on the winding of
the motor. If the insulations are thick there will not be so much space for coils. If
the slot is tight, placing the coil is much more difficult
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Table 2. Old insulation in VSD, H-class motor
Slot insulation
Current insulations (temperature class)
NKN 2525 (H), Nomex-Kapton-Nomex
APGNS (F), Glass cloth-mica laminate bonded
with resin
thickness Mica content
mm
g/m^2
0,25
0,18
120
0,25
400
Total
APGNH (H), Glass cloth-mica laminate bonded
Slot phase insulation with silicone
APGNH (H), Glass cloth-mica laminate bonded
with silicone
NKN 2525 (H), Nomex-Kapton-Nomex
0,68
520
0,18
120
0,18
0,25
120
Total
AOMF (F), Polyester paper with reinforcement
with threads
APGNH (H), Glass cloth-mica laminate bonded
with silicone
APGNH (H), Glass cloth-mica laminate bonded
with silicone
AOMF (F), Polyester paper with reinforcement
with threads
0,61
240
Total
AOMF (F), Polyester paper with reinforcement
Coil group insulation with threads
APGNH (H), Glass cloth-mica laminate bonded
with silicone
AOMF (F), Polyester paper with reinforcement
with threads
Total
0,66
APGUH (H), Glass cloth-mica laminate bonded
with silicone-glass cloth
Phase insulaton in
end coil
0,15
0,18
120
0,18
120
0,15
0,15
0,18
120
0,15
0,48
120
The old insulation group contained a few insulations that were over rated when
compared to the insulation level that is needed. Some of the insulations are wanted to get rid of, because they are very expensive and sometimes hard to get, for
example APGUH. In the old insulation group were used several different insulations. When using same insulation in many places, the storage of the insulations is
easier to manage.
240
30(44)
Table 3. New insulation (solution 1).
Slot insulation
New insulation (temperature class)
NKN 2525 (H), Nomex-Kapton-Nomex
APGNF (F), Class Cloth-mica laminate-polyester paper
Total
Slot phase insulation
NKN 2525 (H), Nomex-Kapton-Nomex
APGNF (F), Class Cloth-mica laminate-polyester paper
thickness
mm
Mica content g/m^2
0,25
0,2
160
0,45
160
0,25
0,2
160
Total
Phase insulaton in end APGNH (H), Glass cloth-mica laminate bonded with
coil
silicone
AOMF (F), Polyester paper with reinforcement with
threads
0,45
160
0,18
120
Total
APGNH (H), Glass cloth-mica laminate bonded with
silicone
AOMF (F), Polyester paper with reinforcement with
threads
0,32
120
0,18
120
Total
0,32
Coil group insulation
0,15
0,15
In the solution 1 were used NKN2525, which has high breakdown voltage and
APGNF which contained mica, which protects motor from partial discharge. The
properties of combination NKN2525 and APGNF are so good, that those can be
used in both the slot and the slots phase insulation, as can be seen in table 3. The
phase insulation is lightened. AOMF can withstand the breakdown voltage and
one APGNH is enough in phase insulation in end coil.
120
31(44)
Table 4. New insulation in VSD, H-class motor (solution 2).
thickness
mm
New insulation (temperature class)
Slot insulation
Mica content
g/m^2
NKN 2525 (H), Nomex-Kapton-Nomex
0,25
NMIN 3209 (H), Nomex-mica bonded with epoxy
resin-nomex
0,24
120
0,49
120
Total
Slot phase insulation NKN 2525 (H), Nomex-Kapton-Nomex
NMIN 3209 (H), Nomex-mica bonded with epoxy
resin-nomex
0,25
0,24
120
Total
APGNH (H), Glass cloth-mica laminate bonded
with silicone
AOMF (F), Polyester paper with reinforcement
with threads
0,49
120
0,18
120
Total
APGNH (H), Glass cloth-mica laminate bonded
Coil group insulation with silicone
AOMF (F), Polyester paper with reinforcement
with threads
0,33
120
0,18
120
Total
0,33
Phase insulaton in
end coil
0,15
0,15
Insulation group 2 is almost the same than insulation group 1. Only difference is
that instead of using APGNF in the slot, NMIN 3209 replaced it. NMIN 3209 is
also very good insulation. NMIN contains mica and it also has high breakdown
voltage. NKN2525 is used mainly to protect NMIN from the stators frame.
120
32(44)
Table 5.New insulation in VSD, H-class motor (solution 3).
Slot insulation
New insulation (temperature class)
NKN 2525 (H), Nomex-Kapton-Nomex
APGNF (F), Class Cloth-mica laminate-polyester
paper
Total
Slot phase insulation
Phase insulaton in
end coil
Coil group insulation
thickness Mica content
mm
g/m^2
0,25
0,2
160
0,45
160
NKN 2525 (H), Nomex-Kapton-Nomex
APGNF (F), Class Cloth-mica laminate-polyester
paper
0,25
0,2
160
Total
APGNH (H), Glass cloth-mica laminate bonded
with silicone
AOMF (F), Polyester paper with reinforcement
with threads
0,45
160
0,18
120
Total
AOMF (F), Polyester paper with reinforcement
with threads
0,33
Total
0,15
0,15
0,15
Insulation group 3 is also almost the same than group 1 but in the coil group insulation APGNH is removed. APGNH were removed because in the thermal class F
is used only one AOMF between coil groups. AOMF is Thermal class F but when
it is impregnated with H-class resin AOMF can with stand the H-class thermal
stress.
120
33(44)
Table 6. New insulation in VSD, H-class motor (solution 4).
Slot insulation
thickness Mica content
mm
g/m^2
0,25
New insulation (temperature class)
NKN 2525 (H), Nomex-Kapton-Nomex
NMIN 3209 (H), Nomex-mica bonded with
epoxy resin-nomex
Total
Slot phase insulation
NKN 2525 (H), Nomex-Kapton-Nomex
NMIN 3209 (H), Nomex-mica bonded with
epoxy resin-nomex
Total
Phase insulaton
APGNH (H), Glass cloth-mica laminate bonded
in end coil
with silicone
AOMF (F), Polyester paper with reinforcement
with threads
Total
Coil group insula- AOMF (F), Polyester paper with reinforcement
tion
with threads
Total
0,24
0,49
0,25
0,24
0,49
120
120
0,18
120
0,15
0,33
120
0,15
0,15
Insulation group 4 is almost the same than insulation group 2. Same as in insulation group 3 the APGNH is removed from the coil group insulation.
All insulation groups were looked over in a meeting with insulation team and production chiefs. Two new insulation groups were designed in meeting. The new
groups are combinations of the four first ones.
120
120
34(44)
Table 7. New insulation in VSD, H-class motor (solution 5).
Slot insulation
Slot phase insulation
Phase insulation in
end coil
Coil group insulation
Current insulations (temperature class)
NMiN 3209 (Nomex-mica laminate-nomex)
APGNF (Polyester fleece-mica laminate-polyester
fleece)
thickness Mica content
mm
g/m^2
0,25
120
0,2
160
Total
NMiN 3209 (Nomex-mica laminate-nomex)
APGNF (Polyester fleece-mica laminate-polyester
fleece)
0,45
0,25
280
120
0,2
160
Total
AOMF (F), Polyester paper with reinforcement
with threads
APGNH (H), Glass cloth-mica laminate bonded
with silicone
0,45
280
0,18
120
Total
AOMF (F), Polyester paper with reinforcement
with threads
0,33
120
Total
0,15
0,15
0,15
The group 5 consists of same coil group and phase insulation in end coil than in
groups 3 and 4. The changes are made in slot insulations. The NKN2525 is replaced with APGNF which is much cheaper than NKN2525. The NKN2525 did
not consist Mica but the APGNF does consist Mica which increase the withstand
of partial discharge.
35(44)
Table 8. New insulation in VSD, H-class motor (solution 6).
Slot insulation
Current insulations (temperature class)
NMiN 3209 (Nomex-mica laminate-nomex)
NMN (Nomex-polyester film-nomex)
thickness Mica
mm
content g/m^2
0,25
120
0,22
Total
0,47
120
NMiN 3209 (Nomex-mica laminate-nomex)
NMN (Nomex-polyester film-nomex)
0,25
0,22
120
Total
APGNW (Class cloth-mica laminate-polyester
paper)
0,47
120
Phase insulaton in
end coil
0,18
160
0,18
160
Coil group insulation
Total
AOMF (F), Polyester paper with reinforcement
with threads
Total
0,15
Slot phase insulation
0,15
A few new insulations are added to the list in group 6 insulation. The NMN is
very cheap and it has high break down voltage withstand property. APGNW is the
also a new insulation in the list. APGNW has got Mica and withstand to breakdown voltage which is required from phase insulation in end coil.
The first combination of insulation in end coil was AOMF+APGNH. These materials were already in use in ABB, in different combinations. The first insulation
group to be tested were almost the same as the end coil phase insulation before.
The only change made was that other AOMF and APGNH were removed. The
first test was the hammer test, because of the mechanical weakness of the glassmica laminate. The hammer test was made both with and without the second
AOMF.
36(44)
Figture 22. Insulation group AOMF+APGNH+AOMF
When using the AOMF on the both sides, the mechanical strength is very good, as
shows above figure 19. Hammer test was made to five insulation pieces and all of
them were acceptable. No ruptures were found. This combination is the present Hclass insulation in VSD motors in the coil group insulation.
37(44)
Figure 23. Insulation group AOMF+APGNH after hammer test
With AOMF+APGNH insulation combinations success in tests were varied. Two
tests of five did not show any kind of rupture or crack in the structure, but three
test pieces were partially cracked. The cracks and ruptures were from1mm to
6mm in size, as above in figure 20. In a closer look the ruptures stopped always
into filament of the AOMF. This means that if the insulation pieces are large
enough they will not rupture in the way that phases can contact. the insulation filaments must be placed normally to coils. Better solutions can be achieved if the
APGNH has a glass cloth on both sides. This increases the mechanical strength of
the APGNH.
As for their electrical properties AOMF and APGNH are excellent for the H-class
VSD motors. AOMF can withstand a 8.8 kV breakdown voltage when impregnated with epoxy resin and APGNH withstands the partial discharge. These properties were already tested.
38(44)
The second insulation that need for test is APGNW. Only information that is not
known is how it withstands mechanical stress. In the hammer test the APGNW
had few ruptures as can be seen in figure 21.
Figure 24. Hammer test result of APGNW
Because of the results of the hammer tests, test winding was made to 450 size stator. In this way the real mechanical strength of the insulation can be measured.
The stator was insulated with three insulations. Every third part of the stator was
insulated with the old and the two new insulation group, group 5 and 6. The stator
was winded normally and after that the stator was disassembled in the way that
the insulation could be investigated. The results showed that the old insulation
group worked well. The shapes of the slot insulations were good and in the phase
insulations did not had any ruptures. The first new insulation group had problems
with the slot insulation. The Insulation (APGNF+NMiN) ruptured from the end to
the frame, as shown in figure 25. This showed that this insulation in the slot does
not have enough mechanical strength. One of the main doubt was the phase insu-
39(44)
lation in end coil (APGNH+AOMF) which had problems in hammer test. Test
winding showed that the phase insulation did not have any problems with the mechanical strength. The second insulation group had problems with the phase insulation. The phase insulation (APGNW) started to rupture and to delaminate in
winding, as shown in figure 26.
Figure 25. Rupture in NMiN+APGNF
Figure 26. Rupture in APGNW
No tests except test winding were made for the slot insulation, because of the information that was received from the insulation manufacturer. The real properties
of the slot insulations are seen in the prototype.
40(44)
When investigating the coil group insulation, if the voltage difference in the same
phases is over 350V then all same phase coil groups must be insulated of each
other, in accordance with FIMOT0345. The most important thing is to think
which insulation is used in the coil group insulation to maintain the good impregnation level. It is not useful to use too thick insulation, if there are thinner insulations that can stand the stresses. The calculation works mainly for the F-thermal
class insulation because in accordance with the H-thermal class instruction all
VSD motors that use more than 500 V D or 660 V Y as rated voltage, every coil
group must be insulated. All the other motors are calculated individuality, as
shown below.
(1)
After this coil pair voltage U2 can be calculated
(2)
Notes:
NR = The number of parallel branches for example when the connection is 3Y,
NR is 3
UN = The effective value of the phase to phase voltage
b = Coefficient. In one-layer winding b is 2. In two-layer winding b is 1.
Note! For two-speed motors, where two windings with different number of poles
form a two-layer structure, b=2 works for both windings.
Information about the impregnation of the resins in the H-class VSD motors was
collected with measurement tool of impregnation. The results were collected since
41(44)
the beginning of year 2012. The result seems to be good when all of the frame
sizes are over 10 %. Information from frame sizes 35 were fed 17 times, frame
size 40 for 99 times and frame sizes 45 for 29 times, as seen in figure 27. When
investigating the impregnation it must be noticed that resin might not be inside of
the stator. In trickle impregnation, the resin is also impregnated to the surface of
the stator and in the vacuum pressure impregnation the surface part is very small.
Figure 27. Impregnation level in old H-class VSD motors
42(44)
8 SOLUTION
The objective in thesis was to reach a good impregnation level and at the same
time maintain good winding properties. All the new solutions are based on the investigation of the insulation datasheets and the prototype. The costs of the insulation were also added to observe.
8.1 Insulation
The new insulation had all the requirements that were wanted. The chosen insulation group for prototypes was modification of table 8 and table 7. The slot insulation is NMiN and NMN. The phase insulation in slot is also NMiN and NMN to
decrease the insulation materials in storage. The phase insulation in the end coil is
AOMF and APGNH. The coil cap insulation is AOMF. This group was chosen
from the hammer test which showed the best mechanical withstand insulations.
8.2 Impregnation level
Because of the lack of time the impregnation test were not made. According to the
measure that was made in 2012 showed that the impregnation level was quite
good and when the insulation is reduced it is very likely that the impregnation
level will increase.
8.3 Cost comparison
Insulation is quite expensive material. The old insulation was made of very expensive materials and materials were used too much. The new insulation group
was 66,7 % cheaper than the old insulation group. The savings that are made with
changing insulations is magnificent. By decreasing the price of the insulation the
motors are more competitive on the markets.
43(44)
9 THE CONCLUSION OF THE WORK
To reach the goal about how insulations work in a real motor, prototypes must be
made. Two prototypes should be ordered. Both prototypes should include the old
winding style and frame but a new insulation group. The stator size could be 315
and it should have 4 poles and the winding style should be double stage overlap.
Both prototypes groups should be trickle impregnated. In the trickle impregnation,
epoxy resin in accordance with FIMOT0345 must be used and in the other stator
polyester resin accordance with FIMOT0345. The prototypes give real information how the new insulation and impregnation ways affects to resins impregnation to stator. To make sure that the insulations will work, the prototypes must be
tested. The first test should be a partial discharge test, where electricity is fed to
stator and the stator is observed in the case of the partial discharge and to it must
be ensure that the insulation can withstand it. The second test is to cut the stator to
pieces and see how well the stator is impregnated.
44(44)
SOURCES
1. ABB Oy introduction. Accessed 14.12.2013 http://new.abb.com/fi/abblyhyesti/yhtyma
2. ABB Oy financial information. Accessed 14.12.2013
http://www.abb.fi/cawp/seitp202/97e23f03abddd323c1257b11005c3e0a.as
px
3. ABB Oy key figures. Accessed 14.12. 2013 http://new.abb.com/about/abbin-brief/key-figures
4. ABB pienjännite koneen käyttöohje. Accessed 30.1.2014
http://www05.abb.com/global/scot/scot259.nsf/veritydisplay/742083e5ed3
0ca63c12579ed003dbeed/$file/Standard_Manual_Low_Voltage_FI_revE
%20lores.pdf
5. ABB Oy. FIMOT0345 / Eristysohje / Staattori / H-luokka / Jännite max.
700 V VSD tai 1000 V DOL
6. ABB Oy. FIMOT1618 / Valutuskyllästysohje.
7. ABB Oy. FIMOT0203 / Tyhjiökyllästysohje.
8. ABB Oy. FIMOT0021 / Kääminnän työohje.
9. Korpinen, L. Sähkökoneet osa 1. Accessed 20.1.2014
http://www.leenakorpinen.fi/archive/svt_opus/10sahkokoneet_1osa.pdf
10. LUT (Lappeenranta University of Technology). Accessed 4.1.2014
https noppa.lut.fi noppa opintoja so bl 0a0 00 ... lu u erist set.pdf
11. Nuorala T. 2013 Breakdown_voltage_tests_060513.
12. Nuorala T. 2013, Development of a test program for flexible laminate insulation in electric machines.
13. Paloniemi. 1987. Sähkö koneiden eristykset.
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