U.S. patent application number 09/891077 was filed with the patent office on 2002-12-26 for pulsed voltage surges resistant enamelled wires.
This patent application is currently assigned to TAI-I ELECTRIC WIRE & CABLE CO., LTD.. Invention is credited to Chang, Yung-Chieh, Du, Chi-Ting, Jang, Chih-Min, Lin, Tsen-Hsu, Lin, Yung-Chin, Liu, Ru-Shi, Tu, Yao-Chung, Wu, Chang-Chin, Wu, Wen-Cheng.
Application Number | 20020197473 09/891077 |
Document ID | / |
Family ID | 21677838 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020197473 |
Kind Code |
A1 |
Jang, Chih-Min ; et
al. |
December 26, 2002 |
Pulsed voltage surges resistant enamelled wires
Abstract
A pulsed voltage surges resistant enamelled wire comprises a
metal conductive wire and at least one shield layer outside the
wire, the shield layer is provided by a coating composition
comprising (a) a synthetic resin, (b) an organic solvent and (c)
metal oxide particles, wherein the metal oxide particles comprise
.alpha.-form Al.sub.2O.sub.3 particles, .gamma.-form
Al.sub.2O.sub.3 particles and transition metal oxide particles.
Inventors: |
Jang, Chih-Min; (Taipei,
TW) ; Liu, Ru-Shi; (Hsinchu Hsien, TW) ; Du,
Chi-Ting; (Taipei, TW) ; Lin, Yung-Chin;
(Chupei City, TW) ; Tu, Yao-Chung; (Hsinchu,
TW) ; Wu, Wen-Cheng; (Taipei, TW) ; Wu,
Chang-Chin; (US) ; Lin, Tsen-Hsu; (Hsinchu,
TW) ; Chang, Yung-Chieh; (US) |
Correspondence
Address: |
Ladas & Parry
26 West 61st Street
New York
NY
10023
US
|
Assignee: |
TAI-I ELECTRIC WIRE & CABLE
CO., LTD.
|
Family ID: |
21677838 |
Appl. No.: |
09/891077 |
Filed: |
June 25, 2001 |
Current U.S.
Class: |
428/375 |
Current CPC
Class: |
H01B 7/292 20130101;
H01B 3/105 20130101; H02K 3/30 20130101; Y10T 428/2933
20150115 |
Class at
Publication: |
428/375 |
International
Class: |
D02G 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2001 |
TW |
090107899 |
Claims
1. A pulsed voltage surges resistant enamelled wire comprising a
metal conductive wire and at least one coating layer outside the
wire, wherein at least one of the coating layer(s) is a shield
layer containing metal oxide particles and the metal oxide
particles comprise .alpha.-form and .gamma.-form Al.sub.2O.sub.3
particles and transition metal oxide particles.
2. The enamelled wire according to claim 1, wherein the shield
layer is provided by a coating composition comprising (a) a
synthetic resin, (b) an organic solvent and (c) metal oxide
particles, wherein the metal oxide particles comprise .alpha.-form
and .gamma.-form Al.sub.2O.sub.3 particles and transition metal
oxide particles.
3. The enamelled wire according to claim 1, wherein the transition
metal oxide is selected from the group consisting of
Cr.sub.2O.sub.3, TiO.sub.2, SiO.sub.2, Zr.sub.2O.sub.3, ZnO and
Fe.sub.2O.sub.3.
4. The enamelled wire according to claim 3, wherein the transition
metal oxide is Cr.sub.2O.sub.3.
5. The enamelled wire according to claim 2, wherein the coating
composition comprises from 3 to 20 parts by weight of metal oxide
particles per hundred parts by weight of the synthetic resin.
6. The enamelled wire according to claim 5, wherein the coating
composition comprises from 5 to 15 parts by weight of metal oxide
particles per hundred parts by weight of the synthetic resin.
7. The enamelled wire according to claim 5, wherein the coating
composition comprises from 2 to 19 parts by weight of transition
metal oxide particles per hundred parts by weight of the synthetic
resin.
8. The enamelled wire according to claim 7, wherein the coating
composition comprises from 5 to 15 parts by weight of transition
metal oxide particles per hundred parts by weight of the synthetic
resin.
9. The enamelled wire according to claim 8, wherein the coating
composition comprises from 5 to 10 parts by weight of transition
metal oxide particles per hundred parts by weight of the synthetic
resin.
10. The enamelled wire according to claim 5, wherein the ratio
between the .alpha.-form Al.sub.2O.sub.3 particles and the
.gamma.-form Al.sub.2O.sub.3 particles is from 1:1 to 1:100.
11. The enamelled wire according to claim 5, wherein the ratio
between the .alpha.-form Al.sub.2O.sub.3 particles and the
.gamma.-form Al.sub.2O.sub.3 particles is from 1:5 to 1:50.
12. The enamelled wire according to claim 5, wherein the ratio
between the .alpha.-form Al.sub.2O.sub.3 particles and the
.gamma.-form Al.sub.2O.sub.3 particles is from 1:5 to 1:15.
13. The enamelled wire according to claim 1, wherein the particle
size of the metal oxide particles is from 0.01 to 5 microns.
14. The enamelled wire according to claim 2, wherein the synthetic
resin is selected from the group consisting of modified or
unmodified polyacetal, polyurethane, polyester, polyesterimine,
polyimine, polyamide, polysulfone, polyimide resins and mixtures
thereof.
15. The enamelled wire according to claim 2, wherein the organic
solvent is selected from the group consisting of cresols,
hydrocarbons, dimethyl phenol, toluene, xylene, ethyl benzene,
N,N-dimethyl formamide, N-methylpyrrolidone, esters, ketones, and
mixtures thereof.
16. The enamelled wire according to claim 2, wherein the coating
composition comprises, based on the total weight of the synthetic
resin and the organic solvent, from 80 to 20 wt % synthetic resin
and from 20 to 80 wt % organic solvent.
17. The enamelled wire according to claim 16, wherein the coating
composition comprises, based on the total weight of the synthetic
resin and the organic solvent, from 75 to 25 wt % synthetic resin
and from 25 to 75 wt % organic solvent.
Description
BACKGROUND OF INVENTION
[0001] It is known that conventional types of speed drives cannot
meet the requirements of efficiency, exactness and cost because of
their high installation cost, smaller torque at slow speed, high
maintenance fee and high energy consumption. Though pulse width
modulated (PWM) type of inverters can meet the aforementioned
requirements, it has been found that the use of PWM inverters
causes premature failure of enamelled wires because of the
inverters' high peak voltage values, pulsed voltage surges and
harmonics, boost up and down, and high switching frequencies.
Specifically, pulsed voltage surges are formed within a very short
time of the order of .mu.sec, and this will cause the temperature
to suddenly increase (i.e. the effect of pulse voltage surges on
temperature is more significant than that of corona discharge). The
sudden increase of temperature will cause the thermal-oxidation
decomposition of the insulation coating layers of enamelled wires
and shorten the lifetime of the wires.
[0002] U.S. Pat. No. 5,654,095 provides an approach to meet the
aforementioned requirements and discloses a pulsed voltage surge
resistant enamelled wire which can withstand voltage surges
approaching 3000 volts and is resistant to a high temperature up to
300.degree. C., wherein the arising rate of the voltage is higher
than 100 kV/.mu.sec and the frequency is less than 20 kHz. The
enamelled wire of U.S. Pat. No. 5,654,095 is characterized by the
addition of metal oxide particles with a particle size of from 0.05
to 1 micron to the shield layer of enamelled wire to provide the
desired pulsed voltage surge resistance. According to the
disclosure of U.S. Pat. No. 5,654,095, metal oxides which can
effectively resist pulse voltage surges and increase the lifetime
of enamelled wires include titanium dioxide, alumina, silica,
zirconium oxide, zinc oxide, iron oxide and various naturally
occurring clays such as in lines 57-59 of column (see column 4,
lines 57-59). Though the examples of U.S. Pat. No. 5,654,095
illustrated the metal oxide as Al.sub.2O.sub.3, they were totally
silent on the structure of Al.sub.2O.sub.3.
[0003] There are two major structures of
Al.sub.2O.sub.3--.alpha.-form and .gamma.-form. .alpha.-form is a
trigonal (R-3CH) structure wherein the lattice constants a=b=4.8
.quadrature. and c=13.0 .quadrature., the lattice angles
.alpha.=.beta.=90.degree. and .gamma.=120.degree.. .gamma.-form is
a cubic (Fd-3mS) structure wherein the lattice constants a=b=c=7.9
.quadrature. and the lattice angles .alpha.=.beta.=.gamma.=90.d-
egree.. The structure of .alpha.-form is more compact than that of
.gamma.-form. In other words, the structure of .gamma.-form is
closer to an amorphous phase and is significantly different from
that of .alpha.-form.
[0004] It has been found that, in the shield layer(s) of an
enamelled wire, the use of both .alpha.-form Al.sub.2O.sub.3
particles and .gamma.-form Al.sub.2O.sub.3 particles can provide
pulsed voltage surge resistance much better than that provided by
.alpha.-form Al.sub.2O.sub.3 particles or .gamma.-form
Al.sub.2O.sub.3 particles alone. This combination has been
disclosed in U.S. Pat. No. 6,136,434. U.S. Pat. No. 6,136,434 is
incorporated here for reference.
[0005] The applicant discovered that, the use of .alpha.-form and
.gamma.-form Al.sub.2O.sub.3 particles in and particles of
transition metal oxide such as Cr.sub.2O.sub.3 in the shield
layer(s) of an enamelled wire, can provide pulsed voltage surge
resistance superior to that provided by the combination of
.alpha.-form Al.sub.2O.sub.3 particles and .gamma.-form
Al.sub.2O.sub.3 particles.
SUMMARY OF THE INVENTION
[0006] It is therefore an object of the invention to provide an
enamelled wire which has increased resistance to insulation
degradation caused by pulsed voltage surges.
[0007] In the broader aspects of the invention, there is provided a
pulsed voltage surge resistant enamelled wire comprising a metal
wire and at least one pulsed voltage surge shield layer overlaying
the metal wire, wherein the shield layer is provided by at least
one polymer containing metal oxide particles dispersed therein, and
wherein the metal oxide particles comprise .alpha.-form and
.gamma.-form Al.sub.2O.sub.3 particles and transition metal oxide
particles. The shield layer containing .alpha.-form and
.gamma.-form Al.sub.2O.sub.3 particles and transition metal oxide
particles can render the enamelled wire to be resistant to pulsed
voltage surges without impairing the other properties of the
enamelled wire.
[0008] These and other objects, advantages and features of the
present invention will be more fully understood and appreciated by
reference to the written specification.
DETAILED DESCRIPTION OF THE INVENTION
[0009] While this specification concludes with claims particularly
pointing out and distinctly claiming that which is considered to be
the invention, it is believed that the invention can be better
understood from a reading of the following detailed description of
the invention.
[0010] Accordingly, the present invention provides an enamelled
wire which comprises a metal wire and at least one coating layer
outside the wire, wherein the components of the at least one
coating layer can be identical or different with the proviso that
at least one of the coating layer contains .alpha.-form and
.gamma.-form Al.sub.2O.sub.3 particles and transition metal oxide
particles. In other words, in case the enamelled wire comprises a
single outside coating layer, the single outside coating layer is
the shield layer which contains .alpha.-form and .gamma.-form
Al.sub.2O.sub.3 particles and transition metal oxide particles;
otherwise, at least one of the outside coating layers is the shield
layer which contains .alpha.-form and .gamma.-form Al.sub.2O.sub.3
particles and transition metal oxide particles.
[0011] The metal wire of the present invention can be in any form,
generally is in circular or rectangular form. As in circular form,
it is preferred that the diameter of the wire is from 0.05 to 3.2
mm, more preferred from 0.10 to 1.5 mm, and most preferred from
0.35 to 1.2 mm.
[0012] Each coating layer of the present invention is provided by a
coating composition comprising (a) a synthetic resin and (b) an
organic solvent. The synthetic resin and organic solvent for the
each coating layer can be identical or different. The coating
composition may optionally comprise other conventional components
suitable for coating layers of an enamelled wire such as dyes,
pigments, dispersants, and the likes. The selected optional
components and their amounts should not affect the desired
properties of the coating layer. Any synthetic resins
conventionally used in enamelled wires can be used in the coating
composition. The synthetic resins used in the present invention can
be, but not limited to, modified or unmodified polyacetal,
polyurethane, polyester, polyesterimide, polyamideimide, polyamide,
polysulfone, polyimide resins, or mixtures thereof. The selection
of synthetic resin depends on the required temperature resistance
and insulation properties on the coating layers. Furthermore,
persons skilled in the art can choose an organic solvent suitable
to the selected synthetic resin. The organic solvent can be, but
not limited to, cresols, hydrocarbons, dimethyl phenol, toluene,
xylene, ethyl benzene, N,N-dimethyl formamide (DMF),
N-methyl-pyrrolidone (NMP), esters, ketones, or mixtures thereof.
The combination of the synthetic resin and the organic solvent is,
based on the total weight of the synthetic resin and the organic
solvent, from 20 to 80 wt % of synthetic resin and from 20 to 80 wt
% of organic solvent, and more preferably from 25 to 75 wt %
synthetic resin and from 75 to 25 wt % organic solvent.
[0013] In order to provide the desired pulsed voltage surges
resistance, the enamelled wire of the present invention comprises
at least outside coating layer which is a shield layer and provided
by a coating containing metal oxide particles, wherein the metal
oxide particles comprise .alpha.-form and .gamma.-form
Al.sub.2O.sub.3 particles and transition metal oxide particles.
Examples of the transition metal oxide are Cr.sub.2O.sub.3,
TiO.sub.2, SiO.sub.2, Zr.sub.2O.sub.3, ZnO and Fe.sub.2O.sub.3, and
Cr.sub.2O.sub.3 is preferred. The particle size of the metal oxide
particles suitable for the present invention is from 0.001 to 10
microns, preferably from 0.01 to 5 microns, and more preferably
from 0.05 to 1.0 micron. It is preferred that the total amount of
the metal oxide particles in a shield layer is, based on 100 parts
by weight of synthetic resin, from 3 to 20 parts by weight (3 to 20
PHR), and from 5 to 15 parts by weight (5 to 15 PHR) is more
preferred. The amount of the transition metal oxide particles in a
shield layer is, based on 100 parts by weight of synthetic resin, 2
to 19 parts by weight (2 to 19 PHR), from 5 to 15 parts by weight
(5 to 15 PHR) is preferred, and from 5 to 10 parts by weight (PHR)
is more preferred. And the amount ratio between the .alpha.-form
Al.sub.2O.sub.3 particles and .gamma.-form Al.sub.2O.sub.3
particles is from 1:1 to 1:100, from 1:5 to 1:50 is preferred, and
from 1:5 to 1:15 is more preferred. The metal oxide particles can
be uniformly dispersed into the coating composition by high shear
mixing or with the use of a mixing apparatus. Optionally, a
dispersant can be used to facilitate the dispersion of the metal
oxide particles and prevent the particles from precipitation. The
amount of dispersant, if used, is from 0.01 to 2 parts by weight
per hundred parts by weight of synthetic resin and organic
solvent.
[0014] Each of the coating layer(s) of an enamelled wire is
provided by applying a corresponding coating composition on the
metal wire, and drying and curing the coating composition.
Generally, the thickness of each layer is from 2.0 to 5.0 mils and
the layer is provided by repeatedly applying the coating
composition on the surface of the wire for five (5) to fifteen (15)
passages. The method of applying the coating depends on the
viscosity of the coating composition. Generally, at 30.degree. C.,
a coating composition having a viscosity higher than 500 cps is
applied by dies, a coating composition having a viscosity of from
100 to 200 cps is applied by a roller and a coating composition
having a viscosity of from 40 to 100 cps is applied by felt. The
speed for applying the coating composition is between 3 and 450
m/min. The coated wire, after each coating layer has been applied,
is fed into a furnace to dry and cure the layer. The temperature of
furnace will depend on the species of coating, the length of
furnace and the thickness of coating layer. Generally, the
temperature at the inlet of the furnace is between 300 and
350.degree. C. and the temperature at the outlet of the furnace is
between 350 and 700.degree. C.
[0015] The following examples are offered by way of illustration.
In the examples, the formulations of coatings and Al.sub.2O.sub.3
particles applied are as follows:
[0016] (1) PAI coating: polyamideimide coating, available from
Tai-I Electric Wire & Cable Co,. Ltd. ROC. as TAI-AIW-31.5,
which can be cured by heating at an elevated temperature, the
solvent of the coating comprises xylene, NMP and DMF, viscosity:
1500 cps/30.degree. C., solid content: 30.2%.
[0017] (2) PEI coating: polyesterimide coating, available from
Nisshoku-Schenectady Kagaku Co. Ltd. Japan as ISOMID-42, which can
be cured by heating at an elevated temperature and through a
transesterification or esterification reaction, the solvent of the
coating comprises xylene, hydrocarbons, cresols and phenol,
viscosity: 2050 cps/30.degree. C., solid contents: 42.2%.
[0018] (3) Al.sub.2O.sub.3 particles: .alpha.-form particles and
.gamma.-form particles, particle size of .alpha.-form=about 0.3
micron, particle size of .gamma.-form=about 0.05 micron.
[0019] (4) Cr.sub.2O.sub.3 particles: particle size=about 0.6
micron
EXAMPLES
Comparative Example C1
[0020] PEI and PAI coatings were separately applied by dies onto
the surface of copper wires having a diameter of 1.024 mm under the
following conditions:
[0021] (i) inner coating layer (the coating layer directly attached
to the copper wire):
[0022] coating: PEI coating
[0023] coating passages: nine (9) passages
[0024] linear coating speed: 9 m/min
[0025] (ii) outer coating layer (the coating layer overlapping the
inner coating layer):
[0026] coating: PAI coating
[0027] coating passages: three (3) passages
[0028] linear coating speed: 9 m/min
[0029] (iii) furnace: length=3.5 m, inlet temperature=360.degree.
C., outlet temperature=480.degree. C.
[0030] The properties of the coated wires are shown in Table I.
Comparative Example C2
[0031] The same as Comparative Example C1 with the exception that
5-10% .alpha.-form Al.sub.2O.sub.3 particles, based on the weight
of synthetic resin, were added to the PAI coating and the
Al.sub.2O.sub.3 particle-containing PAI coatings were mixed at high
stirring speed. The properties of the coated wires are shown in
Table I.
Comparative Example C3
[0032] The same as Comparative Example C1 with the exception that
5-10% .gamma.-form Al.sub.2O.sub.3 particles, based on the weight
of synthetic resin, were added to the PAI coating and the
Al.sub.2O.sub.3 particle-containing PAI coatings were mixed at high
stirring speed. The properties of the coated wires are shown in
Table I.
Comparative Example C4
[0033] The same as Comparative Example 1 with the exception that
5-10% Al.sub.2O.sub.3 particles
(.alpha.-form/.gamma.-form-={fraction (1/9)}), based on the weight
of synthetic resin, were added to the PAI coating and the
Al.sub.2O.sub.3 particle-containing PAI coatings were mixed at high
stirring speed. The properties of the coated wires are shown in
Table I.
1TABLE I Al.sub.2O.sub.3 in dielectric elongation softening heat
lifetime.sup.(2) Ex. upper layer flexibility adherence (kV) (%)
temp. (.degree. C.) shock.sup.(1) (Hr) C1 none Good good 8.86 33.5
402 good 39.4 C2 .alpha.-Al.sub.2O.sub.3 Good good 8.69 32.5 407
good 23.8 C3 .gamma.-Al.sub.2O.sub.3 Good good 9.53 32 419 good 41
C4 (.alpha. + .gamma.)Al.sub.2O.sub.3 Good good 8.92 33 412 good
194.8 Note: .sup.(1)The heat shock test was conducted at
200.degree. C. for one (1) hour according to the NEMAMW-35C
standards, wherein enamelled wires, after having been wound around
a mandrel having a diameter which is three times of the diameter of
the enamelled wires, were tested. .sup.(2)The pulsed voltage surge
lifetime was tested as follows: (i) a twisted pair of enamelled
wires was subjected to the test at a load of 1364 g and each wire
pair was twisted eight (8) revolutions; (ii) one end of the wire
was connected to the output of a frequency inverter and the other
end to a three-phase, 3HP induced generator; the inverter supplied
the generator with an output voltage of 380 V through 100 m of the
wire at a main frequency of 60 Hz, a carrier of 10 kHz and a peak
value of the carrier voltage of sinusoidal square wave of 537 V;
and the test was conducted at the connecting point between the wire
and the generator and in a # 195.degree. C. constant-temperature
furnace.
[0034] As shown in Table I, the pulsed voltage surge lifetime of
the enamelled wires of the present invention wherein the shield
layer contains both .alpha.-form Al.sub.2O.sub.3 particles and
.gamma.-form Al.sub.2O.sub.3 particles is much higher than that of
the enamelled wires wherein the shield layer contains .alpha.-form
Al.sub.2O.sub.3 particles or .gamma.-form Al.sub.2O.sub.3
particles.
Examples 1-4
[0035] The same as Comparative Example 1 with the exception that 1%
Al.sub.2O.sub.3 particles (.alpha.-form/.gamma.-form=1/9) and 0%,
5%, 10%, or 15% Cr.sub.2O.sub.3 particles, based on the weight of
synthetic resin, were added to the PAI coating and the metal oxide
particle-containing PAI coatings were mixed at high stirring speed.
The properties of the coated wires are shown in Table II.
2TABLE II particles in dielectric elongation softening heat
lifetime.sup.(3) Ex. upper layer flexibility adherence (kV) (%)
temp. (.degree. C.) shock (Hr) 1 1%(.alpha. +
.gamma.)Al.sub.2O.sub.3 good good 8.92 33 412 good 2.1 2 1%(.alpha.
+ .gamma.)Al.sub.2O.sub.3 + good good 9.2 33 395 good 6.1
5%Cr.sub.2O.sub.3 3 1%(.alpha. + .gamma.)Al.sub.2O.sub.3 + good
good 9.1 32 376 fair 12.5 10%Cr.sub.2O.sub.3 4 1%(.alpha. +
.gamma.)Al.sub.2O.sub.3 + fair fair 9.0 32 365 fair 27.2
15%Cr.sub.2O.sub.3 Note: .sup.(3)The test requirements of the
pulsed voltage surge lifetime were the same those for the
comparative examples except that the carrier frequency was 15 kHz
and the output voltage was 440 V.
[0036] As shown in Table II, the pulsed voltage surge lifetime of
the enamelled wires of the present invention wherein the shield
layer contains .alpha.-form and .gamma.-form Al.sub.2O.sub.3
particles and transition metal oxide particles, such as
Cr.sub.2O.sub.3 particles, is much higher than that of the
enamelled wires wherein the shield layer contains .alpha.-form
Al.sub.2O.sub.3 particles and .gamma.-form Al.sub.2O.sub.3
particles.
[0037] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *