WO2007139490A1 - Isolation d'enroulement de stator - Google Patents

Isolation d'enroulement de stator Download PDF

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Publication number
WO2007139490A1
WO2007139490A1 PCT/SE2007/050350 SE2007050350W WO2007139490A1 WO 2007139490 A1 WO2007139490 A1 WO 2007139490A1 SE 2007050350 W SE2007050350 W SE 2007050350W WO 2007139490 A1 WO2007139490 A1 WO 2007139490A1
Authority
WO
WIPO (PCT)
Prior art keywords
insulation
particles
electric machine
rotary electric
permittivity
Prior art date
Application number
PCT/SE2007/050350
Other languages
English (en)
Inventor
Eva MÅRTENSSON
Hans-Åke ERIKSSON
Original Assignee
Abb Technology Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Abb Technology Ltd. filed Critical Abb Technology Ltd.
Publication of WO2007139490A1 publication Critical patent/WO2007139490A1/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/30—Windings characterised by the insulating material
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/32—Windings characterised by the shape, form or construction of the insulation
    • H02K3/40—Windings characterised by the shape, form or construction of the insulation for high voltage, e.g. affording protection against corona discharges

Definitions

  • the present invention in a first aspect relates to a rotary electric machine having stator coils with a non-circular cross section, consisting of conductors surrounded by insulation.
  • the invention in a second aspect relates to an elongated conductor having a non-circular cross section and being surrounded by solid insulation.
  • stator bars in a rotary electric machine normally have a non-circular shape, in particular a rectangular shape, and consist of conductors surrounded by insulation.
  • Each bar is normally composed by a number of strands of conducting material such as copper or aluminium. Also the individual strands are insulated.
  • the electrical field must not be allowed to be too high. Due to the peaks at the corners the electrical field in these areas determine the upper limit for what can be allowed, and also limit the general field that can be applied along the straight parts.
  • the object of the present invention is to attain a rotary electric machine in which the variation of the level of, the electrical field in the insulation around the conductor stack of the stator bar is reduced and in particular to reduce the relation between the electrical field at the corners and the electrical field along the sides of the bars.
  • This object according to the first aspect of the invention has been achieved in that a rotary electric machine of the kind in question includes the specific feature that the insulation has a permittivity that varies circumferentially around the bar.
  • the electric field inside the insulation depends inter alia on the permittivity of the insulating material. The higher the permittivity is, the lower the electrical field will be.
  • the insulation By arranging the insulation such that the permittivity thereof varies around the cross section of the bar, the electric field around the bar is affected such that the pattern deviates from the theoretical pattern.
  • the insulation such that the permittivity is higher in these areas where the electric field according to the theoretical pattern is higher than in other parts.
  • the effect will be that the electrical field will be more strongly reduced in these areas than in other parts.
  • stator bars have a cross sectional shape that includes corners and the permittivity of the insulation is higher at the corners than along the sides of the bars, preferably the shape is rectangular.
  • Corners are the most crucial sources for creating a varying electric field level of the theoretical pattern. At each corner a high peak of this level occurs. Normally the electric field at a corner is around three times as high as that at a side of the bar. Therefore the advantages of the present invention are most accentuated when applied to bars having corners. By increasing the permittivity in these areas the relation between the level of the actual electric field can easily be reduced to about two to one.
  • the permittivity of the insulation varies along the sides of the bars.
  • each bar is made up by a plurality of conductor strands each strand creates an increased electric field level at each corner of the strand. Since these corners are located along the sides of the bars these will occur a small peak of the electric field also adjacent to these corners. Although these peaks are of lower magnitude than those at the corners of the complete conductor stack it is of interest to depress also the peaks adjacent the corners of each strand in order to reduce the risk that these minor peaks cooperate with defects in the insulating material.
  • the insulation includes an insulation material having embedded particles.
  • Particles embedded in the insulation material affect the permittivity and resistivity thereof.
  • the particles can be particles of higher permittivity than the base material of the insulation or can be particles having general field grading properties.
  • the extent to which the particles affect the permittivity and resistivity of the insulation depends on the concentration of the particles in the base material.
  • particles in this application is ment particles of any shape, thus not only spherical particles but also particles in the shape of for example flakes or fibres.
  • the particles include particles having resistive field grading properties and/or particles having capacitive field grading properties.
  • Resistive field grading particles can be used in alternating current as well as direct current applications.
  • Capacitive field grading particles are mainly suitable for alternating current applications.
  • the particles include particles of a permittivity of at least 5 at infinitely high frequencies, preferably a material chosen from the group containing AI 2 O 3 , TiO 2 and BaTiO 3 .
  • the particles include particles of semiconducting material, preferably chosen from the group containing ZnO and SiC.
  • semiconducting material is defined as a material having an energy bandgap in the range from OeV to 5eV.
  • the insulation includes a tape wound around each bar, the particles being embedded in the tape.
  • Insulation made up by wound tape e.g. mica tape is the most commonly used structure.
  • This kind of insulation automatically leads to an increase in the permittivity at the corners when the tape includes permittivity increasing particles.
  • the filler concentration increases, the particles come closer to each other and contact each other with higher pressure. The effect is that the permittivity increases in these areas.
  • a decrease of the thickness with a certain percentage results in an increase in the permittivity with a percentage that is much higher.
  • the size of the particles is in the range of 1 nm to 0,1 mm, preferably in the range of 5 nm to 0,02 mm.
  • the upper limit of the range is limited by the thickness of the tape which typically is about 0,15 mm.
  • the lower limit of the range is limited by what can practically be obtained.
  • particles of a size about 1 nm can be obtained by modern nanotechnique, a size of about 5 nm is more conveniently attained.
  • the size in this application is to be understood the smallest dimension of the particle, i.e. the diameter of a spherical particle, the thickness of a flake or the diameter a fibre respectively.
  • the dimension in the other directions might be much larger, up to the mm- range.
  • each bar includes a plurality of conductor strands, where each strand is surrounded by individual insulation and the permittivity and/or the resistivity varies in the circumferential direction around the strand.
  • the object has been met by providing the conductor with an insulation that has a permittivity that varies in the circumferential direction.
  • the conductor has a cross sectional shape that includes corners, preferably a rectangular shape, and the permittivity of the insulation is higher at the corners than along the sides of the conductor.
  • the insulation is of a kind that corresponds to any of those described above for the insulation of the stator bars in the electric machine.
  • the invented conductor and the preferred embodiments thereof have similar advantages as have been described above for the invented electric machine and the preferred embodiments thereof.
  • a component is provided that is particularly suitable for constituting the bars when manufacturing an electric machine and also in other applications when it is described to affect the pattern of the electric field outside the conductor.
  • Fig 1 is a cross section through a stator bar according to the invention
  • Fig 2 is a graph illustrating the level of the electric field around the bar
  • Fig 3 is a graph similar to that of fig 2, illustrating a part thereof more detailed
  • Fig 4 is a partial cross section through the insulation of a bar according to an alternative example
  • Fig 1 is a cross section through a typical stator bar 1 of a rotary electric machine.
  • the bar 1 in this case is composed of six strands 2 of copper.
  • Each strand 2 has a rectangular cross sectional shape having the smallest dimension in the radial direction of the machine.
  • the complete bar 1 made up of the strands has a rectangular cross sectional shape with the largest dimension in the radial direction of the machine.
  • Each strand 2 is surrounded by an individual conductor insulation 4, and the whole conductor stack is surrounded by a main insulation 3.
  • the voltage applied to the conductors generates an electric field inside the conductor insulation 4 and main insulation 3.
  • the electric field should generally be as high as possible in order to obtain maximum power.
  • the electric field however has to be limited in order to avoid destructive partial discharges.
  • the electric field varies around the bar, having a general level along the side 5 of the bar and sharp peaks at each corner 6 of the bar. This creates a contradiction in that the electrical field at the corners determines the upper limit of what can be allowed regarding the level of the electric field, whereas the level of the generated electrical field along the sides 5 of the bar, the level which is related to the power of the machine, is much lower.
  • the present invention reduces this problem by reducing the relation between the peak field at the corners 6 and the general field along the sides 5. This is attained by increasing the permittivity of the insulation 3 in the area of the corners 6, which has the effect that the electrical field in these areas is reduced.
  • the power of the machine can be increased by increasing the level of the general electric field along the sides but still maintaining the peak field at a level that is acceptable.
  • This effect is illustrated in a graph in fig 2 showing the electric field E as a function of the circumferential location s.
  • the curve A represents the variation of the electric field for a machine having conventional insulation and the curve B represents the corresponding field for a machine having insulation according to the invention,
  • the conventional machine has a general level G 0 of the electrical field and peaks and the corner at a level P.
  • the relation between G 0 and P is typically about
  • the general electrical field has been raised to the level G 1 . Due to the higher permittivity of the insulation at the corners the electrical field around these can be kept at the same level P as for a conventional machine. With the invention it can be achieved that the relation between Gi and P can be reduced to about 1 :2,5.
  • G 0 and G 1 thus will be in the order of 1 :1 ,2 indiacting an increase in power of about 20%. Decreasing the peakfields at the corners can be made in various ways such as changing the shape of the conductors and increasing the thickness of the insulation in these areas or by using another material, which has an increased permittivity in these areas.
  • the main insulation 3 typically consists of mica tape wound around the bar.
  • the mica tape according to this invention is made as a special composite tape including particles that increase the permittivity of the material.
  • the material of the particles is chosen from these mentioned above as being particularly advantageous in this application.
  • other materials having similar resistive or capacitive field grading properties could be employed, such as various other metal oxides, mixed metal oxides, silicon carbide or silica.
  • the increase in permittivity is high at the corners 6 than along the sides 5 due to the effect of a raised winding pressure at the corners.
  • the tape does not necessarily need to be a mica tape.
  • Various polymer materials can be used.
  • the particles can be embedded either in the mica layer or in the substrate layer or in both.
  • the size of the particles is in the nano or micro-meter range and should be as uniform as possible.
  • the amount of particles is in the range of 5 to 40 volume %, preferably in the range of 20-30 volume %.
  • the strand insulation 4 is built up in a corresponding way.
  • the electric field will normally have small peaks at the corners of the strands.
  • a more detailed presentation of the pattern of the electric field around the bar therefore will show a plurality of minor peaks also along the sides 5 of the bar as illustrated in fig 3, where P s represent these minor peaks.
  • curve B represents a machine where the main insulation 3 but not the strand insulation 4 is made according to the invention.
  • Curve C represents a machine where also the strand insulation 4 is based on the principle according to present invention. As can be seen also these minor peaks are reduced in the electric field pattern for a machine according to this embodiment.
  • the peaks P at the corners of the bar is at the highest level and thus determines the electrical stress that can be allowed it is also of interest to reduce those minor peaks P s at the strand corners. In certain situations where there are local material defects or unforeseen irregular electric stresses one of the minor peaks could cause damage to the machine. Reducing also these peaks therefore allows a further increase to the level G 2 of the general electric field, and gives a better robustness of the insulation.
  • Figure 4 illustrates an alternative example of the invention, and depicts a part of the insulation 3 around the bar.
  • the insulation in this case is not built up by wound tape but an extruded polymeric material.
  • particles 7 are injected into the material at the corners, which particles have permittivity-increasing properties.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Insulation, Fastening Of Motor, Generator Windings (AREA)

Abstract

La présente invention concerne une machine électrique rotative qui possède des barres de stator (1) avec des torons conducteurs (2) qui présentent une section transversale non circulaire et qui sont entourés par une isolation (3). Selon l'invention, l'isolation (3) possède une permittivité qui varie dans la direction circonférentielle. Ainsi, le niveau relatif des pointes du champ électrique à l'intérieur de l'isolation peut être réduit. L'invention concerne également un conducteur oblong. (Figure 1)
PCT/SE2007/050350 2006-05-29 2007-05-24 Isolation d'enroulement de stator WO2007139490A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0601182 2006-05-29
SE0601182-9 2006-05-29

Publications (1)

Publication Number Publication Date
WO2007139490A1 true WO2007139490A1 (fr) 2007-12-06

Family

ID=38778907

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE2007/050350 WO2007139490A1 (fr) 2006-05-29 2007-05-24 Isolation d'enroulement de stator

Country Status (1)

Country Link
WO (1) WO2007139490A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2403113A1 (fr) 2010-07-02 2012-01-04 Alstom Technology Ltd Barre de stator
JP2014087101A (ja) * 2012-10-19 2014-05-12 Toyota Motor Corp 回転電機の固定子

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4760296A (en) * 1979-07-30 1988-07-26 General Electric Company Corona-resistant insulation, electrical conductors covered therewith and dynamoelectric machines and transformers incorporating components of such insulated conductors
US6043582A (en) * 1998-08-19 2000-03-28 General Electric Co. Stable conductive material for high voltage armature bars
WO2000060721A1 (fr) * 1999-04-01 2000-10-12 Alstom Uk Ltd. Ameliorations apportees a des machines electriques
US20020029897A1 (en) * 2000-09-14 2002-03-14 Younsi A. Karim Graded electric field insulation system for dynamoelectric machine
US6359232B1 (en) * 1996-12-19 2002-03-19 General Electric Company Electrical insulating material and stator bar formed therewith

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4760296A (en) * 1979-07-30 1988-07-26 General Electric Company Corona-resistant insulation, electrical conductors covered therewith and dynamoelectric machines and transformers incorporating components of such insulated conductors
US6359232B1 (en) * 1996-12-19 2002-03-19 General Electric Company Electrical insulating material and stator bar formed therewith
US6043582A (en) * 1998-08-19 2000-03-28 General Electric Co. Stable conductive material for high voltage armature bars
WO2000060721A1 (fr) * 1999-04-01 2000-10-12 Alstom Uk Ltd. Ameliorations apportees a des machines electriques
US20020029897A1 (en) * 2000-09-14 2002-03-14 Younsi A. Karim Graded electric field insulation system for dynamoelectric machine

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2403113A1 (fr) 2010-07-02 2012-01-04 Alstom Technology Ltd Barre de stator
EP2403114A1 (fr) 2010-07-02 2012-01-04 Alstom Technology Ltd Barre de stator
US8952256B2 (en) 2010-07-02 2015-02-10 Alstom Technology Ltd. Stator bar
JP2014087101A (ja) * 2012-10-19 2014-05-12 Toyota Motor Corp 回転電機の固定子

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