JPS605747A - Insulated coil - Google Patents

Abstract

PURPOSE:To provide an insulated coil having long voltage applying lifetime by providing a semiconductive layer on a strand bundle or a turning insulator of the upper and lower end turns of the linear portion of a coil. CONSTITUTION:A semiconductive layer 15 having 10-10<6>OMEGA of surface resistivity is formed on the end turn formed of a conductor 1 and the insulator 10, i.e., the outer layer of the first turn and the final turn. The layer 14 is formed on the portion which enters the core slot and the range of 5-30mm. from the end of the core. Then, a main insulator 5 is formed on the entire periphery of the coil by the lap winding of an insulating tape or the flat winding of an insulating sheet. Then, a corona preventive layer 6 is formed on the linear portion of the coil of the outer layer. In this manner, since an electric field of the corner of the conductor which becomes the starting point of an insulation breakdown can be alleviated, a tree can be suppressd from the coil to increase the voltage applying lifetime.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an insulated coil mainly used in rotating electric machines.

[Technical background of the invention and its problems]

As an example of an insulated coil, a rotating electric machine coil will be explained.

FIG. 1 shows a typical cross-sectional view of a portion of a rotary turn coil for a stator of a rotating electrical machine that is inserted into an iron core slot. It consists of a wire conductor (1) and a covering insulation (2). A plurality of wires (3) (four wires in FIG. 1) are combined into one turn. Insulate each turn with turn insulation (4), and after stacking the required number of turns, apply main insulation (5), and further prevent corona by applying low-resistance paint or wrapping low-resistance tape or sheet around the outer periphery. Apply layer (6). However, if the turn voltage or voltage is low, turn insulation may not be applied. Since the corona prevention layer (6) is in contact with the core slot wall, it has the same potential as the core, that is, the ground potential. In FIG. 1, from the second turn onwards, the strands within the turns are simplified. Draw the following figures in the same way. When conducting a dielectric breakdown test or energized life test of such a coil,
The corner of the conductor at the end turn, ie, the P section in FIG. 1, is the starting point of breakage. The electric field near the corner of the conductor is measured using the concentric cylinder model shown in FIG. Element wire conductor (1)
The radius of curvature of the corner of is kr+, and 0 [phase] is the strand insulation (
2) and insulation including turn insulation (4). When the applied voltage is v, the insulation thickness is d, and the dielectric constant of the insulation part and (5) are equal, the distance from the surface of the wire conductor (1) is
The electric field E (x) at point P is expressed by the following formula, ■ r10%, 6+m, d-2m, V = 10k
The calculated value of the electric field in the case of V (D is shown in Figure 3. The electric field is x
= Maximum value at 0 (11,37kV/mI+), X
= Minimum value at 2 (2,62kVAm) 'jr,
It can be seen that the electric field is concentrated near the wire conductor.

Therefore, in conventional rotating machine coils, the electric field concentrates near the wire conductors, causing dielectric breakdown, making it difficult to improve the breakdown voltage or extend the energized life.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an insulated coil that has a low electric field near a wire conductor, therefore has a high dielectric breakdown voltage, and has a long energized life.

[Summary of the invention]

In order to achieve the above object, in the insulated coil of the present invention, semiconducting jψ is provided on the wire bundle of the turns at the upper and lower ends of the coil straight portion or on the turn insulation.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described using FIG. 4. FIG. 4 is a sectional view of a straight portion of the coil. conductor(
1) and its insulation 00 (with turn insulation, IOΩ~IO
A semiconducting layer a4) of Ω is provided.

The semiconductive layer u4) may be a polymer film such as polyester or polyimide, a nonwoven fabric such as polyester or polyamide, glass cloth impregnated or coated with carbon-filled resin, or a mixture of polymer fiber and carbon fiber. However, other materials (for example, A Carbon manufactured by Nippon Aroma Co., Ltd.) can be used. No semiconducting layer I is provided in the middle turns. The semi-conductive layer 114) is applied to the part of the core that enters the slot and the area that extends from the end of the core to 50 m to 30 m.

Thereafter, the main insulation (5) is completely formed around the entire circumference of the coil by wrapping an insulating tape in layers or flatly wrapping an insulating sheet. Next, a corona prevention layer (6) is formed on the straight portion of the outer layer of the coil. After this, depending on the type of insulation, impregnation, curing treatment, or heat molding treatment is performed.

The surface resistivity of the semiconducting layer 011) is 1 so that the potential can be considered to be the same over the entire circumference of the semiconducting layer C1 (l).
0 Ω or less, and 100 or more so that eddy current loss due to leakage magnetic flux can be ignored. When the surface resistivity of the semiconducting layer becomes %lOΩ or more, it approaches the impedance at the commercial frequency between the semiconducting layer I and the conductor (1), and the semiconducting layer 04
), which causes loss and is not desirable. The potential of this semiconducting layer (b) is
) and the conductor (1) and the capacitance C3-8 and the semiconducting layer I
and the capacitance C3-G between the slot wall and the corona prevention layer (6), which has the same potential.

Equivalent circuits for determining all of these capacitances are shown in FIGS. 5 and 6. If the potential of the conductor (1) is '6V, then the voltage V between the conductor +1+ and the semiconducting layer I. -8 and semiconducting layer I
The voltage vS-G between and the anti-corona layer (6) is expressed as follows. However, since the potential difference between the conductors of the end turn and the adjacent turn is small, the calculations are made here assuming that they are at the same potential.

■ C-8L 10cc-8/C8゜vs-c ”” VC-8 Here C6-8-3CI+ 2C*+4CsC8-G
#C4+2C5+2C6 Cc-s is the capacitance between the conductor of the next turn and the semiconducting layer 04) in addition to the entire circumference of the end turn, whereas C8-1
; is composed of only three sides facing the semiconductive layer α and the corona prevention layer (6), so the difference in C6-8 is greater than the difference in insulation thickness.
is larger than C3-G. Therefore conductor (1)
and the semiconducting layer I. -8 becomes a very small value, and the electric field just above the corner of the conductor (1), where the electric field would be maximum in the absence of the semiconducting layer [14], decreases significantly.

In this case, the maximum electric field occurs on the outer surface (convex side surface) of the R portion of the semiconductor layer '4L o4) instead of directly above the corner of the conductor.

However, since the radius of curvature of that portion is thicker than that of the corner of the conductor, the concentration of the electric field is relaxed and the radius of curvature is not so large. The vicinity of the corner of the conductor is modeled as a concentric cylinder as shown in FIG. 7, and the result of calculating the electric field at a point at a distance X from the surface of the conductor (1) is shown by a solid line a in FIG. The calculation conditions for Fig. 8 are as follows: width of l-turn conductor y = lQ-shape,
Thickness of conductor of 1 turn t-10, d4-Q, 3+o
+, thickness of the semiconducting layer d2=0.05, thickness of the main insulation ds-1, 65+s, distance from the conductor surface to the inside of the anti-corona layer d=2. onm, applied voltage V=lOkV
For comparison, the electric field distribution in the case where the polarity inversion shape and dimensions are the same but the semiconducting layer α4) is removed is already shown in broken line in FIG. Maximum electric field without semiconducting layer is 11.37 kV
/nan, whereas the maximum electric field when the semiconducting layer of the present invention is introduced is 9.46 kV/m+n, which is 16.
The maximum electric field can be reduced by 8%.

Next, we will examine the electric field distribution of a coil whose main insulation thickness is completely reduced. With the same configuration as Figures 5 and 7, W = 10 + Oka,
t=l0ran, rl=0.6m, dl
=0.3m+n, d2=0.05, and the maximum electric field is 11.37 when there is no semiconducting layer as described above.
95 factor of 1cV/+nm or 10.8]cV/nu
The main insulation thickness ds (= d d+ dz
) is calculated as ds”'1.3ho (d=1.65 tone)
becomes. The electric field distribution in this case is shown in FIG. 9a. The broken line C in the figure is the electric field distribution when there is no semiconducting layer and the insulation thickness d is equal to the same as the broken line in FIG. Similarly, when a, = o, 4sM, the maximum electric field is 10.81
If you request the thickness of the main insulation to be cV 7mm, then ds-1
, 07 side (d=1.57). The electric field distribution in this case is shown in FIG. 9b. In the above embodiment, the semiconducting layer of the present invention is introduced, and the insulation distance d between the conductor and the semiconducting layer is 0.
．． When it is set to 3 mm, the insulation thickness d' including the semiconducting layer is reduced by a factor of 17.5, and when d is combined with the total 0.45 + m++, the maximum electric field is reduced by 21.5%, and the maximum electric field is lower than that of the conventional configuration. The value can be kept 5 inches lower than the value of the coil.

Next, if a semiconductive material is wrapped in an insulating layer, we will examine whether the electric field will be abnormally concentrated at its edges. A longitudinal cross-sectional view of the vicinity of the core end of the coil of the present invention is shown in FIG. The coil is inserted into the slot of the iron core 0η, and the corona prevention layer (6) is extended 20 mm beyond the end of the iron core.
An electric field relaxation layer σψ is provided on the creeping surface of the coil, partially overlapping the end portion thereof. (1) is a conductor.

(If) is insulation including wire insulation or turn insulation when there is turn insulation, and (5) is main insulation. The semiconductive layer α is provided longer than the corona prevention layer (6). With the structure of the present invention, the electric field inside the semiconducting layer I is suppressed to a very low level as shown in FIG.
Although the electric field is concentrated at end A of ), it does not become so high toward the conductor side. In addition, there is an electric field relaxation layer ue on the coil surface B corresponding to the position of the end A of the semiconducting layer I, and due to the effect of this electric field relaxation layer, the voltage between A and B is several tens of tens of degrees lower than that in the core. %, and the electric field directed from the end A of the semiconducting layer α toward the coil surface layer is also sufficiently relaxed. In the case of low-voltage models without the electric field relaxation layer (I [9) on the coil surface, the coil surface potential is determined by the corona prevention layer (
6) After exiting end C (core end if there is no corona prevention layer), the electric field rapidly approaches the conductor potential, so the electric field directed from the end of the semiconducting layer (I4) toward the outer surface is lower than when there is an electric field relaxation layer. It will be further relaxed.

Even if a surge voltage is applied to the coil and a voltage is generated between the turns, the semi-conductive layer 04) is separated by the earthwork, so there will be no flooding over between the semi-conductive layers.
The coil surge it M'fr does not decrease.

Note that although the semiconducting layer in FIG. 4 wraps around the entire circumference of the end turn, there is no problem even if there is a portion that is not connected as shown in FIGS. 11 and 12. In particular, when there is a break in the semiconducting layer on the adjacent turn side as shown in Figure 12, C8
,, remain the same, but CC-8 becomes smaller and the conductor (1
) and the semiconducting layer I, while conversely producing the effect of completely reducing the electric field on the outer surface of the semi-conducting layer I (2j1 electric field kj L+4) which produces the maximum electric field.

Further, even if a semiconducting layer is provided on the outer periphery of not only one turn at the end but also two or three turns including the end turn, the maximum electric field can be reduced in the same manner as in the above case. FIG. 13 shows a cross section of a coil wrapped in a semiconductive layer (b) of two turns at each end. The reference numerals in this figure are the same as in FIG. 4. However, when the turn configuration of the coil is the same, the more turns are wrapped together, the more the voltage between the conductor (1) of the turn and the semiconductor layer U4) increases when a steep surge enters the coil. get higher,
Therefore, there is a possibility that the insulation 0 [is dielectrically broken down.

Therefore, when adopting the entire configuration as shown in FIG. 13, it is necessary to investigate and consider in advance the type, magnitude, and frequency of surges that will occur in the system to which the rotating machine is connected.

It goes without saying that the same effect can be obtained even if the number of turns wrapped in the semiconductive layer Q4) is changed between the upper and lower sides of the coil cross section.

〔Effect of the invention〕

As explained above, according to the present invention, the electric field at the corners of the conductor, which is the starting point of dielectric breakdown, can be completely relaxed, so that tree generation can be suppressed and the energized life can be significantly extended compared to conventional coils. 1. If the maximum electric field is the same as that of conventional coils, the insulation thickness can be reduced by about 20%, and the rated current increases due to the improvement of the space factor in the core slot and the heat transfer coefficient, resulting in smaller equipment. can greatly contribute to the development of

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the straight part of the insulating coil of a conventional rotating machine.
Fig. 2 is a drawing showing a model for calculating the electric field near the conductor corner in Fig. 1, Fig. 3 is a curve diagram showing the electric field distribution near the conductor corner of the conventional coil, and Fig. 4 is a diagram showing the electric field distribution near the conductor corner of the conventional coil. 5 is a capacitance distribution diagram for calculating the electric field near the corner of the conductor shown in Fig. 4, Fig. 6 is an equivalent circuit of Fig. 5, and Fig. The figure is a model diagram for calculating the electric field near the conductor corner of Fig. 4, and Fig. 8 shows the electric field distribution near the conductor corner of the coil of the present invention calculated using the model of Fig. 7 compared to the conventional coil. A curve diagram shown for comparison, Figure 9 is the 7th
The maximum electric field calculated using the model shown in the figure is 9
A curve diagram showing the electric field distribution near the conductor corner of the coil of the present invention in which the insulation thickness is thinned so that the insulation thickness is 5. 1st
2 and 13 are cross-sectional views of coils showing other embodiments of the present invention. ■...Element wire conductor 2...#'η insulation 3...Cumulative &
! 4...Turn insulation 5...Main insulation 6...Corona prevention layer IO...Material insulation of strands and turn insulation 10-Gb thin insulation 16...Electric field relaxation layer 17...Substitute for iron core Person Patent Attorney Noriyuki Chika (1 person) Fig. 1 Fig. 2 Fig. 3 Distance 2 (Kehler Fig. 4 Fig. 5 Fig. 6 = Fig. 7. Fig. 8 Conductor-Uno Distance) λ (Prayer-1) Fig. 9 Groove A Main η・Ra C Distance l (γm) Fig. 10/7 Fig. 11

Claims (1)

[Claims] +1) Electric wire w? N turns several times to form a multi-turn, and a semi-conducting layer is provided on the surface of the outermost turn insulation.
An insulated coil characterized by a ground insulating gold film surrounding all turns and housed in an iron core slot. (2) The insulated coil according to claim 1, wherein the longitudinal end of the coil of the semiconducting electric layer is located under the electric field relaxation layer applied to the surface of the ground insulation. .