JP4640681B2

JP4640681B2 - Rotating electric machine

Info

Publication number: JP4640681B2
Application number: JP2007325933A
Authority: JP
Inventors: 敏和紙上; 信一郎栃尾
Original assignee: 西芝電機株式会社
Priority date: 2007-12-18
Filing date: 2007-12-18
Publication date: 2011-03-02
Anticipated expiration: 2027-12-18
Also published as: JP2009148140A

Description

本発明は回転電機の機内通風冷却構造の改善に係り、特に固定子コイルの均一な冷却構造に関する。 The present invention relates to an improvement of an in-machine ventilation cooling structure of a rotating electrical machine, and more particularly to a uniform cooling structure of a stator coil.

直流機、同期機、誘導機などの回転電機は、構造面では回転子と固定子とから構成されており、機能面では電磁誘導原理を利用して、電気エネルギーと機械エネルギー（回転エネルギー）の相互変換を行うものである。回転電機を運転すると、鉄損、銅損、機械損、風損などの損失が発生し、この損失の大部分は熱エネルギーに変換されて機器の温度上昇を招く。回転電機内部には絶縁物が使用されており、この絶縁物が熱によって変化し、温度が高いほど絶縁性能は悪くなり寿命が短くなる。絶縁物が劣化すると、焼損や短絡事故の発生が高くなるので回転電機における温度上昇は重要なポイントである。したがって規格でも許容最高温度・温度上昇限度が規定されている。なお、この許容最高温度・温度上昇限度は絶縁物の構成材料によって決まる絶縁階級によって異なる。一般にいわゆる７℃の法則と言われるように、各主絶縁材料の使用温度が７〜１０℃上昇するごとにその寿命は半減すると言われている。 Rotating electrical machines such as DC machines, synchronous machines, and induction machines are composed of a rotor and a stator in terms of structure, and in terms of functions, using electromagnetic induction principles, electrical energy and mechanical energy (rotational energy) Mutual conversion is performed. When a rotating electrical machine is operated, losses such as iron loss, copper loss, mechanical loss, and windage loss occur, and most of this loss is converted into thermal energy, leading to an increase in the temperature of the device. An insulator is used inside the rotating electrical machine. This insulator changes due to heat, and the higher the temperature, the worse the insulation performance and the shorter the life. When the insulator deteriorates, the occurrence of burnout and short-circuit accidents increases, so the temperature rise in the rotating electrical machine is an important point. Therefore, the standard also defines the maximum allowable temperature and temperature rise limit. The allowable maximum temperature and the temperature rise limit vary depending on the insulation class determined by the constituent material of the insulator. It is said that the lifetime is halved every time the operating temperature of each main insulating material rises by 7 to 10 ° C., as generally called the so-called 7 ° C. law.

そのため回転電機では内部に冷却ファンを設け、このファンによって強制通風して冷却する方法が採用され、開放形のように回転電機の外部から空気を取り入れ、この空気を回転電機内部に循環させて冷却後の空気を回転電機の外部に排出する方式、全閉外扇形のように内部の空気と外部の空気を遮断し、回転電機のフレームをファン等により機械的に強制通風して外部から冷却する方式、あるいは冷却媒体を冷却機もしくは熱交換器によって冷却する内冷形など種々の方式が実用化されている。この場合、効果的に冷却するために電気鉄板を積層して回転子及び固定子を製作する際に、ある一定の間隔で通風用のダクトを設けて鉄心及び鉄心内のコイルを冷却する構造としている。 For this reason, a rotating fan is provided with a cooling fan inside, and forced to ventilate and cool by this fan. Air is taken from outside the rotating electric machine as in the open type, and this air is circulated inside the rotating electric machine for cooling. A method of discharging the air after the outside of the rotating electrical machine, a system that shuts off the internal air and the external air like a fully closed external fan, and cools the frame of the rotating electrical machine mechanically with a fan etc. Various systems such as an internal cooling type in which a cooling medium is cooled by a cooler or a heat exchanger have been put into practical use. In this case, when manufacturing rotors and stators by stacking electric iron plates for effective cooling, a structure for cooling the iron core and the coils in the iron core by providing ventilation ducts at certain intervals Yes.

しかし、これらの従来の冷却方式は回転子及び固定子に冷却媒体をファンによって通風し熱を取り去ることで冷却することに終始して、より効率的に冷却することまでは着目していない。すなわち、一例として従来から使用されている同期発電機の冷却構造を図９、図１０−１、図１０−２及び図１１に基いて説明する。図９は従来の両吸い込み通風形同期発電機を簡略化した構成図であり、軸中心から上部の断面を示している。図１０−１は従来の同期発電機の固定子鉄心を通過する冷却媒体の通風量の分布、及び図１０−２は固定子コイルの温度分布を示す曲線図である。図１１は数千ｋＷ〜数万ｋＷ程度の中容量同期発電機の軸方向断面図の一例である。 However, these conventional cooling systems do not pay attention to cooling more efficiently, starting with cooling by passing a cooling medium through the fan and removing heat from the rotor and stator. That is, the cooling structure of the synchronous generator conventionally used as an example is demonstrated based on FIG. 9, FIG. 10-1, FIG. 10-2, and FIG. FIG. 9 is a schematic view of a conventional double-suction ventilation type synchronous generator, showing a cross section from the center to the upper part. FIG. 10-1 is a curve diagram showing the distribution of the air flow rate of the cooling medium passing through the stator core of the conventional synchronous generator, and FIG. 10-2 is a curve diagram showing the temperature distribution of the stator coil. FIG. 11 is an example of an axial sectional view of a medium capacity synchronous generator of about several thousand kW to several tens of thousands kW.

図９の左右はほぼ対称であるから、説明を簡単にするために右側部分について説明する。 Since the left and right sides of FIG. 9 are substantially symmetric, the right part will be described for the sake of simplicity.

吸入ファン１によって吸気口２から吸入された冷却媒体３は、回転子４の軸方向通風部５に流入し、回転子４を冷却する。回転子４を冷却した冷却媒体３は固定子の自己通風遠心ファン効果により、固定子フレーム１４に取り付けられた固定子６に軸に対して直角の方向に吹き付けられる。この冷却媒体３は固定子６の鉄心に或る間隔で設けられた通風ダクト７を通って固定子６に発生した熱量を奪い去り冷却する。 The cooling medium 3 sucked from the suction port 2 by the suction fan 1 flows into the axial ventilation portion 5 of the rotor 4 and cools the rotor 4. The cooling medium 3 that has cooled the rotor 4 is sprayed in a direction perpendicular to the axis to the stator 6 attached to the stator frame 14 by the self-ventilated centrifugal fan effect of the stator. The cooling medium 3 cools by removing heat generated in the stator 6 through a ventilation duct 7 provided at a certain interval in the iron core of the stator 6.

この構造では図１１の中央部軸方向断面図に於いて、シャフト１１の軸方向に冷却媒体３が軸方向通風部５に沿って吹き付けられるが、シャフト１１に取り付けられた回転子スパイダー４−１に設けられた例えば凸形の回転子磁極４−２の間の軸方向通風部５を通って回転子磁極４−２を冷却する。上述したように、冷却媒体３は回転子磁極４−２を冷却した後、固定子６に吹きつけられ、図１１では図示していないが図９の固定子通風ダクト７を経て固定子６を冷却して温度が上昇している冷却媒体３は、固定子６の鉄心の外周部に排出される。また全閉形回転電機では固定子フレーム１４が円周部全体に取り付けられているので、固定子から排出された上記冷却媒体３は固定子６の鉄心とフレーム１４との間隙を通って吸気口２へと循環する。開放形回転電機にあっては、この冷却媒体は排気口２’から外部に排気される。 In this structure, the cooling medium 3 is sprayed along the axial ventilation portion 5 in the axial direction of the shaft 11 in the axial sectional view of the central portion of FIG. 11, but the rotor spider 4-1 attached to the shaft 11. For example, the rotor magnetic pole 4-2 is cooled by passing through the axial ventilation portion 5 between the convex rotor magnetic poles 4-2 provided in FIG. As described above, the cooling medium 3 cools the rotor magnetic pole 4-2, and then is blown onto the stator 6. Although not shown in FIG. 11, the cooling medium 3 passes through the stator ventilation duct 7 in FIG. The cooling medium 3 whose temperature has been increased by cooling is discharged to the outer peripheral portion of the iron core of the stator 6. Further, in the fully closed rotating electric machine, the stator frame 14 is attached to the entire circumference, so that the cooling medium 3 discharged from the stator passes through the gap between the iron core of the stator 6 and the frame 14 and the intake port 2. Circulate to In the open type rotating electrical machine, the cooling medium is exhausted to the outside through the exhaust port 2 '.

しかし、回転子４に対して流れる冷却媒体の量は、遠心ファン効果により軸方向に進んで中央部に近づくにつれて減少する。これは図１０−１に示すように固定子通風ダクトを通過する冷却媒体３の通風量分布が中央部近辺で少なく、端部で多くなる。一方、固定子コイル８のコイルエンド９では必要以上の冷却媒体量で冷却されている。すなわち図１０−２に示すように、固定子６の中央部では冷却媒体量が少ないため固定子コイルの温度は比較的高くなるが、端部では冷却媒体量が多いために温度は低くなる。換言すれば固定子コイルはその場所によって高温、中温、低温という不連続な温度分布となっている。 However, the amount of the cooling medium flowing with respect to the rotor 4 decreases in the axial direction due to the centrifugal fan effect and approaches the central portion. As shown in FIG. 10A, the air flow distribution of the cooling medium 3 passing through the stator air duct is small near the center and large at the end. On the other hand, the coil end 9 of the stator coil 8 is cooled with an amount of cooling medium more than necessary. That is, as shown in FIG. 10-2, the temperature of the stator coil is relatively high because the amount of the cooling medium is small at the center portion of the stator 6, but the temperature is low because the amount of the cooling medium is large at the end portion. In other words, the stator coil has a discontinuous temperature distribution of high temperature, medium temperature, and low temperature depending on the location.

この通風量のバランスを図り固定子コイル８の温度上昇を均一にするために、１００ＭＷクラスの大型ターボ発電機では、例えば特許文献１の例に示されているように、固定子通風ダクトを軸方向中央部では数多く設け、端部では数を少なくして中央部により多くの冷却媒体を通過させるようにする方法、あるいは通風ダクトの幅を中央部ほど広くして端部に行くにつれて狭くした通風ダクトを設けるなどで固定子コイル中央部の温度上昇を抑える方法が開示されている。また、特許文献２では、固定子フレームと固定子鉄心との間に周方向に連続した通風路を軸方向に複数設け、これらの通風路のうち少なくとも鉄心の軸方向中央部と連通する通風路に対応して冷却器を設置して、冷却された媒体を鉄心の軸方向中央部に鉄心の外周側から内周側に向かって流す方法が開示されている。 In order to balance this air flow rate and make the temperature rise of the stator coil 8 uniform, in a 100 MW class large turbo generator, for example, as shown in the example of Patent Document 1, the stator air duct is pivoted. Provide a large number at the center in the direction and reduce the number at the end to allow more cooling medium to pass through the center, or the width of the ventilation duct is wider at the center and the ventilation is narrower toward the end. A method of suppressing a temperature rise at the center of the stator coil by providing a duct or the like is disclosed. In Patent Document 2, a plurality of circumferentially continuous ventilation paths are provided between the stator frame and the stator iron core in the axial direction, and among these ventilation paths, the ventilation path communicates with at least the axial central portion of the iron core. A method is disclosed in which a cooler is installed correspondingly to flow the cooled medium from the outer peripheral side of the iron core toward the inner peripheral side in the axially central portion of the iron core.

上述のように、回転電機では固定子コイル８に温度分布が生ずるため、固定子コイル８は軸方向位置に対して熱膨張が不均一になり、コイルの絶縁物にストレスが生じ、また亀裂や絶縁破壊が発生することがある。また固定子コイル８中央部の最高温度箇所を適正温度に冷却するためには吸入ファン１の容量を、コイル８の温度を規定温度以下に冷却するのに十分な容量とすればよいが、その場合には通風量が多くなり、中央部以外の固定子コイル８では必要以上の通風量となり、また吸入ファン１の容量も大きくなって、回転電機の総合効率にも影響を及ぼすことになる。 As described above, since the temperature distribution is generated in the stator coil 8 in the rotating electric machine, the stator coil 8 has a non-uniform thermal expansion with respect to the axial position, stress is applied to the coil insulator, cracks, Dielectric breakdown may occur. Further, in order to cool the maximum temperature portion of the center portion of the stator coil 8 to an appropriate temperature, the capacity of the suction fan 1 may be set to a capacity sufficient to cool the coil 8 to a specified temperature or less. In this case, the amount of ventilation increases, and the stator coil 8 other than the central portion has an amount of ventilation more than necessary, and the capacity of the suction fan 1 increases, which affects the overall efficiency of the rotating electrical machine.

さらに特許文献１の通風ダクトを位置により粗密にしたり、或いはダクト幅を粗密にする方法は非常に有効ではあるが、比較的大量生産する中小型機においては固定子鉄心の枚数違い、中央部と端部との取り違いなど製作工程上複雑となり、製作時間が余計に必要となるなどの問題点が発生する。また特許文献１のように、別に冷却機を設けて中央部のみ冷却を促進する方法は、固定子６の外周部の通風ダクトの構造が複雑となり、中小型機では採用することは難しい。 Furthermore, although the method of making the ventilation duct of Patent Document 1 coarse or dense depending on the position or making the duct width dense is very effective, in a small and medium-sized machine that is relatively mass-produced, the number of stator cores differs, The manufacturing process, such as misalignment with the end, becomes complicated, and problems such as extra manufacturing time are required. In addition, as in Patent Document 1, a method of separately providing a cooler and promoting cooling only at the center part complicates the structure of the ventilation duct on the outer peripheral part of the stator 6 and is difficult to employ in a small and medium-sized machine.

本発明は上記の点に鑑みてなされたものであり、図１１の固定子６の鉄心と固定子フレーム１４との間隙部分に、固定子鉄心の外周部側に鉄心端部では狭い間隔、鉄心中央部では広い間隔とした抵抗板を設置することにより、固定子ダクトを通過する冷却媒体を軸方向に対して均一化して、回転電機の固定子コイルを均一に冷却し、且つ製作が容易で高効率の回転電機を提供することを目的とする。
特開２００３−２１９６０６号公報特開２００２−１７０７０号公報 The present invention has been made in view of the above points, and in the gap portion between the iron core of the stator 6 and the stator frame 14 in FIG. By installing a resistor plate with a wide interval in the center, the cooling medium passing through the stator duct is made uniform in the axial direction, the stator coil of the rotating electrical machine is cooled uniformly, and manufacturing is easy. An object is to provide a highly efficient rotating electrical machine.
JP 2003-219606 A JP 2002-17070 A

本発明は上記の目的を達成するために、固定子と、回転子と、この回転子の両軸端に設けられた軸流ファンと、この軸流ファンにより吸入した冷却媒体を前記回転子の軸方向通風部に流して、前記回転子の自己通風遠心ファン効果によって回転子を冷却した冷却媒体を前記固定子の通風ダクトに流して、固定子通風ダクトの外周部に吐出する通風システムとからなる回転電機において、前記固定子の外周部に、固定子端部では固定子に近接して、固定子中央部近傍では固定子と離れた位置に一体形の固定子通風ダクト押えを取り付ける構造にある。 In order to achieve the above object, the present invention provides a stator, a rotor, an axial fan provided at both axial ends of the rotor, and a cooling medium sucked by the axial fan. A cooling medium that flows through the axial ventilation section, cools the rotor by the self-ventilated centrifugal fan effect of the rotor, flows through the stator ventilation duct, and discharges the cooling medium to the outer periphery of the stator ventilation duct; In the rotating electrical machine, an integrated stator ventilation duct presser is attached to the outer periphery of the stator, close to the stator at the stator end, and away from the stator near the center of the stator. is there.

さらに、固定子通風ダクト押えの中央部近傍をダクトと平行になるように外周側へ延長し、その間に１枚または複数枚の整流板を設ける構造、固定子フレームを固定子鉄心の外周部に軸方向とほぼ直角に突き出させ、その間に１枚または複数枚の整流板を設ける構造、あるいは固定子通風ダクト押えの代わりに、固定子フレームを固定子の外周部に向かって突出させる構造などによって通風抵抗を変化するようにし、前記固定子通風ダクトを通過する冷却媒体の流量を一定にして固定子コイルを効率的に冷却すると共に、前記ファンの容量を小さくすることで冷却媒体の流量を必要最小限に最適化することを特徴とした回転電機である。 Furthermore, a structure in which the vicinity of the center portion of the stator ventilation duct presser is extended to the outer peripheral side so as to be parallel to the duct, and one or more current plates are provided therebetween, and the stator frame is provided on the outer peripheral portion of the stator core. Protruding almost perpendicularly to the axial direction and providing one or more rectifying plates between them, or using a structure in which the stator frame protrudes toward the outer periphery of the stator instead of the stator ventilation duct holder Ventilation resistance is changed, the flow rate of the cooling medium passing through the stator ventilation duct is kept constant, the stator coil is efficiently cooled, and the capacity of the fan is reduced, so that the cooling medium flow rate is required. It is a rotating electrical machine characterized by being optimized to the minimum.

本発明では固定子ダクトを通過する冷却媒体の通風抵抗を軸方向中央部で小さくし、端部で大きくするために、固定子通風ダクト押さえを新規に設け、その形状と構造を考慮することにより、固定子通風ダクトを通過する流量を均一にすることが可能であり、或いは固定子通風ダクト押さえを使用しなくても固定子通風ダクトの吐出側にある固定子フレームを固定子通風ダクトの位置に応じて調整することによって、固定子通風ダクトを通過する冷却媒体の通風量をほぼ均一化することが可能になる。その結果として、固定子コイルの温度が最も高くなる中央部付近を、余裕を以って冷却することが可能となり、逆に中央部付近を冷却するための必要十分な通風量に減少させることができるため、軸の両端部に設ける軸流ファンを小型化することが可能である。さらに固定子通風ダクトを設けることや、固定子フレームを切り欠くことは難しい作業ではないので、本発明によれば高効率で複雑化しない回転電機を供給できる。この発明は回転電機の機種の如何にかかわらず、開放形、全閉形、自冷形、他冷形構造に適用できる利点がある。 In the present invention, in order to reduce the ventilation resistance of the cooling medium passing through the stator duct at the center in the axial direction and increase it at the end, a stator ventilation duct holder is newly provided, and the shape and structure thereof are taken into consideration. It is possible to make the flow rate through the stator ventilation duct uniform, or the stator frame on the discharge side of the stator ventilation duct can be positioned on the stator ventilation duct without using the stator ventilation duct holder. By adjusting according to this, it becomes possible to make the ventilation amount of the cooling medium passing through the stator ventilation duct substantially uniform. As a result, it becomes possible to cool the vicinity of the central portion where the temperature of the stator coil is highest with a margin, and conversely, it is possible to reduce the ventilation rate to a necessary and sufficient amount for cooling the vicinity of the central portion. Therefore, it is possible to reduce the size of the axial fan provided at both ends of the shaft. Furthermore, providing a stator ventilation duct and notching the stator frame are not difficult operations. Therefore, according to the present invention, it is possible to supply a rotating electric machine that is highly efficient and not complicated. The present invention has an advantage that it can be applied to an open type, a fully closed type, a self-cooling type, and other cooling type structures regardless of the type of rotating electrical machine.

以下本発明の実施形態を図面に基づいて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

（実施形態１）
同期機は周知のように主に固定子と回転子とから構成され、外部から固定子に電源が与えられると固定子コイルではその電源により回転磁界を発生する。また回転子では直流により励磁されると磁極が発生し、相互の電磁作用によって回転子は回転して外部に回転エネルギーを供給する電動機となる。また反対に外部から回転エネルギーが与えられ、且つ回転子側が直流で励磁されると、その磁力で固定子側に電力を発生する発電機となる。同機器は２極機のように高速機器では回転子構造は円筒形となり、４極以上の中・低速機では凸極形が多い。 (Embodiment 1)
As is well known, the synchronous machine is mainly composed of a stator and a rotor. When power is supplied to the stator from the outside, the stator coil generates a rotating magnetic field by the power. When the rotor is excited by direct current, a magnetic pole is generated, and the rotor rotates by the mutual electromagnetic action to become an electric motor that supplies rotational energy to the outside. On the other hand, when rotational energy is applied from the outside and the rotor side is excited with a direct current, the generator generates electric power on the stator side by the magnetic force. In the case of high-speed equipment, such as a 2-pole machine, the rotor structure is cylindrical.

図１は本発明の実施形態１の両吸い込み通風形回転電機、特に凸極形同期機を簡略化した構成を示したものであり、軸中心から上部の断面を示している。凸極形同期機は図９に示したように、シャフト１１の上に回転子スパイダー４−１を介して極数分の磁極４−２が取り付けられており、回転電機外部または内部の図示しない別の電源から直流を供給されて磁極を構成する。一方、固定子側には多数のスロットがあって、この内部に絶縁物で厳格に絶縁されたコイルが収められており、この固定子コイル５から発生する熱量を冷却するための通風ダクト７が固定子６に設けられている。 FIG. 1 shows a simplified configuration of a double-suction ventilating rotary electric machine according to Embodiment 1 of the present invention, particularly a convex-polar synchronous machine, and shows a cross section from the center of the shaft to the upper part. As shown in FIG. 9, the convex pole type synchronous machine has poles 4-2 corresponding to the number of poles attached to the shaft 11 via a rotor spider 4-1, and is not shown outside or inside the rotating electrical machine. A magnetic pole is formed by supplying direct current from another power source. On the other hand, there are a large number of slots on the stator side, in which a coil strictly insulated with an insulator is housed, and a ventilation duct 7 for cooling the amount of heat generated from the stator coil 5 is provided. It is provided on the stator 6.

図１の左右はほぼ対称であるから、簡単のために右側部分について説明する。軸流の吸入ファン１によって吸気口２から吸入された冷却媒体３は、回転子４の磁極間の軸方向通風部５に流れて行き、回転子４を冷却する。また回転子４の自己通風遠心ファン効果によっても回転子４を冷却しており、固定子フレーム１４に取り付けられた固定子６の鉄心に、遠心力により軸に対して直角方向に吹き付けられる。一方固定子フレーム１４に図１に示す形状の通風ダクト押え１０を取り付けるものとする。前記の固定子表面に到達した冷却媒体は通風ダクト７を通って図１の上部方向に流れるが、このとき端部の固定子通風ダクトを通過する冷却媒体３−１は通風ダクト押え１０に遮られるため通風抵抗が大きくなり、その通風量が少なくなる。ここで減少した通風量は軸方向中央部に押し出されるため、短部よりやや中央寄りの固定子通風ダクト７を通過する冷却媒体３−２の通風量が増加する。しかし、この冷却媒体３−２も固定子通風ダクトを通過して固定子６の背面へ抜けようとするが、固定子ダクト押え１０に遮られるため通風抵抗が大になり、従って通風量が減少する。しかし、固定子通風ダクト押え１０と固定子通風ダクト７との間隔は端部における両者の間隔より広いためその通風抵抗は端部より小さく、従って通風量は冷却媒体３−１の場合より多くなる。冷却媒体３−２が固定子通風ダクト７を通過する際に減少した通風量も軸方向中央部に押し出されるが、軸中央部の固定子ダクト７を通る冷却媒体３−３の通風損失は図１の通風ダクト押えの形状から明らかなように上記冷却媒体３−２より小さくなり、通風量が多くなる。すなわち従来方式では、冷却媒体３の通風量が一定であるから、通風ダクト押えの形状を適宜製作することにより、各通風ダクト７を通過する冷却媒体３−１、３−２、３−３はほぼ同じ通過量となる。 Since the left and right sides in FIG. 1 are substantially symmetrical, the right side portion will be described for the sake of simplicity. The cooling medium 3 sucked from the intake port 2 by the axial flow suction fan 1 flows to the axial ventilation portion 5 between the magnetic poles of the rotor 4 to cool the rotor 4. The rotor 4 is also cooled by the self-ventilated centrifugal fan effect of the rotor 4 and is blown to the iron core of the stator 6 attached to the stator frame 14 in a direction perpendicular to the axis by centrifugal force. On the other hand, the ventilation duct holder 10 having the shape shown in FIG. The cooling medium that has reached the stator surface flows through the ventilation duct 7 in the upper direction of FIG. 1. At this time, the cooling medium 3-1 passing through the stator ventilation duct at the end is blocked by the ventilation duct holder 10. Therefore, ventilation resistance increases and the ventilation volume decreases. Since the reduced ventilation rate is pushed out to the axially central portion, the ventilation rate of the cooling medium 3-2 passing through the stator ventilation duct 7 slightly closer to the center than the short portion increases. However, the cooling medium 3-2 also passes through the stator ventilation duct and tries to escape to the back surface of the stator 6. However, since the cooling medium 3-2 is blocked by the stator duct retainer 10, the ventilation resistance increases, and therefore the ventilation volume decreases. To do. However, since the gap between the stator ventilation duct presser 10 and the stator ventilation duct 7 is wider than the gap between the two at the end portion, the ventilation resistance is smaller than that at the end portion. Therefore, the ventilation amount is larger than that in the cooling medium 3-1. . The amount of air flow that is reduced when the cooling medium 3-2 passes through the stator ventilation duct 7 is also pushed out to the axial center, but the ventilation loss of the cooling medium 3-3 through the stator duct 7 at the axial center is shown in FIG. As apparent from the shape of the 1 air duct presser, the cooling medium is smaller than the cooling medium 3-2 and the air flow is increased. That is, in the conventional method, since the ventilation amount of the cooling medium 3 is constant, the cooling mediums 3-1, 3-2 and 3-3 passing through the respective ventilation ducts 7 are appropriately manufactured by appropriately forming the shape of the ventilation duct holder. The passing amount is almost the same.

この通風量の分布を示す図２−１で更に詳しく説明する。すなわち図２−１で（１）の曲線は従来方式の場合の冷却媒体通過量を示したものであり、固定子中央部では上記の通り通風量が少なくなる。その結果として、固定子温度は図２−２の従来方式の固定子温度分布を示す曲線（１’）のように、軸方向中央部付近では冷却媒体の通過する量が少ないため、固定子コイル８は最も高い温度となり、通風量が多い端部では冷却媒体の通過量がより多いため、固定子コイル８の温度は低い。 This will be described in more detail with reference to FIG. That is, the curve (1) in FIG. 2-1 shows the cooling medium passage amount in the case of the conventional method, and the ventilation amount decreases as described above at the center of the stator. As a result, the stator coil has a small amount of cooling medium passing near the central portion in the axial direction as shown in the curve (1 ′) showing the stator temperature distribution of the conventional system in FIG. 8 is the highest temperature, and at the end portion where the air flow rate is large, the passage amount of the cooling medium is larger, so the temperature of the stator coil 8 is low.

図２−１の曲線（２）は本発明の実施形態１による通風量を示す曲線であって、冷却媒体３−１、３−２、３−３がほぼ同じ通過量となっており、固定子全体に亘って均一となっている。その結果、図２−２の実施形態１の固定子温度分布を示す曲線（２’）のように、固定子温度がほぼ全体に亘って一定である。しかし、従来方式では軸方向中央部の最小通風量でも中央部の固定子コイル８の温度が規定温度を超えないように通風量を決定する必要があるが、本発明の実施形態１によれば、同容量の吸気ファンでは冷却能力に余裕がある。一般に軸方向中央部の通風量により必要とする冷却媒体３の量が決まり、比較的大型の吸気ファンが使用されていたのである。本発明では通風ダクト押え１０により通過する通風量を均一化するが、この均一化の原理を図３でさらに説明する。図３は横軸に通風量［ｍ^３／ｓｅｃ］、縦軸に圧力［ｍｍＡｑ］／通風抵抗［ｍｍＡｑ］を取って、必要風量を求める曲線図である。いま図９に示す従来構造での通風量に対する通風抵抗曲線をＡ、そのときのファンの圧力曲線をＣとすると、固定子通風ダクトに流れる必要最低通風量はＡ曲線とＣ曲線との交点で定まるから、ｅ［ｍ^３／ｓｅｃ］となる。しかるに本発明の構造にすると、固定子ダクト押え１０を配置してあるため、通風抵抗が大きくなり圧力曲線はＡ曲線からＢ曲線となるので、必要最小通風量はＡ曲線とＣ曲線との交点で定まるｆ［ｍ^３／ｓｅｃ］まで減少する。この場合の風量が図２−１の（２）で示す均一化された通風量となる。 A curve (2) in FIG. 2-1 is a curve showing the air flow rate according to the first embodiment of the present invention, and the cooling media 3-1, 3-2, and 3-3 have substantially the same passing amount, and are fixed. It is uniform over the entire child. As a result, like the curve (2 ′) showing the stator temperature distribution of the embodiment 1 in FIG. 2-2, the stator temperature is substantially constant throughout. However, in the conventional method, it is necessary to determine the ventilation amount so that the temperature of the stator coil 8 in the central portion does not exceed the specified temperature even with the minimum ventilation amount in the central portion in the axial direction, but according to the first embodiment of the present invention. The intake fan with the same capacity has a sufficient cooling capacity. In general, the amount of cooling medium 3 required is determined by the amount of ventilation in the central portion in the axial direction, and a relatively large intake fan is used. In the present invention, the amount of air passing through the ventilation duct holder 10 is made uniform, and the principle of this uniformity will be further described with reference to FIG. FIG. 3 is a curve diagram for obtaining the necessary air volume, with the horizontal axis representing the air flow [m ³ / sec] and the vertical axis representing the pressure [mmAq] / ventilation resistance [mmAq]. Assuming that the ventilation resistance curve with respect to the ventilation rate in the conventional structure shown in FIG. 9 is A and the pressure curve of the fan at that time is C, the necessary minimum ventilation rate flowing through the stator ventilation duct is the intersection of the A curve and the C curve. Since it is determined, e [m ³ / sec] is obtained. However, in the structure of the present invention, since the stator duct presser 10 is disposed, the ventilation resistance increases and the pressure curve changes from the A curve to the B curve. Therefore, the necessary minimum ventilation amount is the intersection of the A curve and the C curve. It decreases to f [m ³ / sec] determined by. The air volume in this case is the uniform air volume shown in (2) of FIG.

本発明では、通風量は軸方向に対して均一化されているため、図２−２の（２’）に示すように軸中央部の固定子コイルの温度は規定温度最高値以下であるが、この固定子温度を規定温度にほぼ等しい値まで上昇させ、且つ軸方向全体に亘って必要最低風量が確保できれば、吸入ファンをより小型にすることが可能となる。すなわち図３において、小型化したファンの圧力曲線をＤ曲線とすると、Ｂ曲線とＤ曲線の交点により決まる風量ｇ［ｍ^３／ｓｅｃ］が絶縁物の劣化を防ぐ必要最小風量となる。 In the present invention, since the air flow rate is made uniform in the axial direction, the temperature of the stator coil at the center of the shaft is not more than the specified maximum temperature as shown in (2 ′) of FIG. If the stator temperature is increased to a value substantially equal to the specified temperature and the necessary minimum air volume can be secured over the entire axial direction, the suction fan can be made smaller. That is, in FIG. 3, when the pressure curve of the downsized fan is a D curve, the air volume g [m ³ / sec] determined by the intersection of the B curve and the D curve is the minimum necessary air volume to prevent the deterioration of the insulator.

従って本発明の構造では固定子コイルの温度も軸方向に対し規定温度で均一化され、従来構造のようにコイルエンド９の過剰冷却は発生しない。しかもファンを小さくすることが可能であり、回転電機の効率が増加する。この場合の通風量を図２−１のファンを小型化した場合の通風量曲線（３）に示す。また、その結果としての固定子コイル温度は図２−２の曲線（３’）で示される。 Therefore, in the structure of the present invention, the temperature of the stator coil is also made uniform at a specified temperature with respect to the axial direction, and the coil end 9 is not excessively cooled unlike the conventional structure. In addition, the fan can be made small, and the efficiency of the rotating electrical machine increases. The ventilation amount in this case is shown in the ventilation amount curve (3) when the fan of FIG. The resulting stator coil temperature is shown by the curve (3 ') in FIG.

すなわち本発明によれば、固定子通風ダクト押え１０を設けることにより、固定子コイルを均一に冷却することが可能となり、かつ吸入ファンを最適設計となる小型化が可能になるので、より効率が高い回転電機を提供することができる。 That is, according to the present invention, by providing the stator ventilation duct presser 10, the stator coil can be uniformly cooled, and the suction fan can be downsized to an optimum design, so that the efficiency can be improved. A high rotating electrical machine can be provided.

（実施形態２）
次に本発明の実施形態２を、実施形態１を示す図１と同一部分に同一符号を付した図４に基いて説明する。図４の実施形態２が図１の実施形態１と異なる点は、固定子通風ダクト押え１０の中央部近傍に固定子通風ダクト１２を固定子通風ダクト７と平行になるように外周部へ延長し、且つ整流板１３をその間に設けている点である。したがって排気の際の通風抵抗が小さくなり通風量が増加するので、固定子コイル８の中央部近辺の冷却効果をより高めると共に、吸入ファンによる機械損が更に減少して、回転電機の効率を更に高めることがその特徴となっている。 (Embodiment 2)
Next, a second embodiment of the present invention will be described based on FIG. 4 in which the same reference numerals are given to the same parts as those in FIG. The second embodiment of FIG. 4 is different from the first embodiment of FIG. 1 in that the stator ventilation duct 12 is extended to the outer periphery so as to be parallel to the stator ventilation duct 7 near the center of the stator ventilation duct holder 10. In addition, the current plate 13 is provided between them. Accordingly, the ventilation resistance during exhaust is reduced and the ventilation volume is increased, so that the cooling effect in the vicinity of the center portion of the stator coil 8 is further enhanced, and the mechanical loss due to the suction fan is further reduced, further improving the efficiency of the rotating electrical machine. The feature is to increase.

従って本発明の実施形態１と比べて、固定子コイル８の中央部近辺を特に効率よく冷却すると共に、固定子コイル全体をより均一に冷却するため、なお一層の高効率化が可能な回転電機を提供することができる。 Therefore, compared with the first embodiment of the present invention, the vicinity of the center portion of the stator coil 8 is particularly efficiently cooled, and the entire stator coil is more uniformly cooled. Can be provided.

（実施形態３）
実施形態３を示す図１と同一部分を同一符号で示す図５は、本発明の実施形態３の両吸込み通風形回転電機の主要部を示す構成図である。実施形態３では実施形態１を示す図１のように、固定子通風ダクト押え１０を設けずに図５に示すように固定子フレーム１５を固定子６の鉄心中央部で切り欠いた構造としている。この実施形態３では、吸入ファン１により吸気口２から吸入された冷却媒体３は回転子の軸方向通風部５の方に流れて行き、回転子４を冷却する。また回転子４の自己通風遠心ファン効果によっても回転子４を冷却した後に、固定子６の鉄心へ軸に対して直角方向に吹き付けられる。このとき端部の固定子通風ダクト７を通過する冷却媒体３−１は、固定子通風ダクトを通って固定子６の鉄心の背面側に抜けようとするが、固定子フレーム１５に遮られるため通風抵抗が大きくなり、その通風量が少なくなる。ここで減少した通風量は軸方向に押し出されるため、端部よりやや中央寄りの固定子通風ダクト７を通る冷却媒体３−２の通風量の方が多くなる。しかしこの冷却媒体３−２も固定子通風ダクト７を通って固定子鉄心の背部に抜けようとするが、固定子フレーム１５に部分的に遮られ、通風抵抗が大きくなって通風量がやや減少する。ここで減少した通風量も軸方向中央部に押し出されるため、中央寄りの固定子ダクトを通る冷却媒体３−３の通風量が多くなり、冷却媒体３−１、３−２、３−３はほぼ同じ通風量となる。 (Embodiment 3)
5 which shows the same part as FIG. 1 which shows Embodiment 3 with the same code | symbol is a block diagram which shows the principal part of the both suction ventilation type rotary electric machine of Embodiment 3 of this invention. In the third embodiment, as shown in FIG. 1 showing the first embodiment, the stator ventilation duct presser 10 is not provided and the stator frame 15 is cut out at the center of the iron core of the stator 6 as shown in FIG. . In the third embodiment, the cooling medium 3 sucked from the suction port 2 by the suction fan 1 flows toward the axial ventilation portion 5 of the rotor and cools the rotor 4. Also, the rotor 4 is cooled by the self-ventilated centrifugal fan effect of the rotor 4 and then blown to the iron core of the stator 6 in a direction perpendicular to the axis. At this time, the cooling medium 3-1 passing through the stator ventilation duct 7 at the end tends to escape to the back side of the iron core of the stator 6 through the stator ventilation duct, but is blocked by the stator frame 15. Ventilation resistance increases and the ventilation volume decreases. Since the reduced air flow rate is pushed out in the axial direction, the air flow rate of the cooling medium 3-2 passing through the stator air duct 7 slightly closer to the center than the end portion is increased. However, this cooling medium 3-2 also tries to pass through the stator ventilation duct 7 to the back of the stator iron core, but is partially blocked by the stator frame 15, increasing the ventilation resistance and slightly reducing the ventilation volume. To do. Since the reduced air flow amount is also pushed out to the central portion in the axial direction, the air flow amount of the cooling medium 3-3 passing through the stator duct closer to the center increases, and the cooling mediums 3-1, 3-2, and 3-3 The air flow is almost the same.

しかし、実施形態１の固定子通風ダクト押え１０と、実施形態３の固定子フレーム１５とを比較すると、図１の固定子通風ダクト押え１０と通風ダクトの間隔は端部では狭く、中央部で広くなっているため通風抵抗はほぼ連続的に変化するのに対し、実施形態３では固定子フレーム１５と固定子通風ダクト７との間隔は一定であり、中央部では固定子フレーム１５がないため通風抵抗は不連続である。図６−２において、曲線（１）は従来方式、（３）は実施形態１と同様に吸入ファンを小型化した場合の温度分布を示している。そのため固定子通風冷却媒体の通風量は、図６−１の（３）曲線に示すように完全には均一化されていないが、従来方式に比べればある程度均一化されている。その結果としての固定子コイル８の温度は図６−２の（３’）曲線に示すように軸方向中央部では規定最高温度より低く、固定子通風ダクト押え１０が無くても実施形態１とほぼ同様の効果が得られる。 However, comparing the stator ventilation duct holder 10 of the first embodiment with the stator frame 15 of the third embodiment, the distance between the stator ventilation duct holder 10 and the ventilation duct of FIG. The ventilation resistance changes substantially continuously because it is wide, whereas in the third embodiment, the interval between the stator frame 15 and the stator ventilation duct 7 is constant, and there is no stator frame 15 in the center. Ventilation resistance is discontinuous. In FIG. 6B, a curve (1) shows a conventional method, and (3) shows a temperature distribution when the suction fan is downsized as in the first embodiment. For this reason, the ventilation rate of the stator ventilation cooling medium is not completely uniformed as shown by the curve (3) in FIG. 6A, but is uniformed to some extent as compared with the conventional method. As a result, the temperature of the stator coil 8 is lower than the specified maximum temperature in the axial center as shown by the curve (3 ′) in FIG. 6B, and even if the stator ventilation duct holder 10 is not provided, Almost the same effect can be obtained.

実施形態３によれば、固定子通風ダクト押え１０を省略し、固定子フレーム１５を固定子６の中央部を切り欠くことにより、ほぼ同様の効果が得られるので、ファン１の小型化による高効率性、経済性、製作の容易性などの特徴を有する回転電機を提供することができる。 According to the third embodiment, since the stator ventilation duct presser 10 is omitted and the stator frame 15 is cut out at the center of the stator 6, almost the same effect can be obtained. It is possible to provide a rotating electrical machine having characteristics such as efficiency, economy, and ease of manufacture.

（実施形態４）
実施形態２を示す図４と同一部分を同一符号で示す図７は、本発明の実施形態４の両吸い込み通風形回転電機、特に凸極形同期機を簡略化した構成の主要部を示す構成図である。実施形態４が実施形態２と異なる点は、図４の固定子通風ダクト１２を図７のように固定子フレーム１７の中央部付近で固定子通風ダクト７と平行になるよう外周部へ延長しており、その間に整流板１３を設けている点である。従って実施形態４は、実施形態１と実施形態３の両方の特性を有し、実施形態３を改良した実施形態である。実施形態３では通風量が完全に均一ではないが、実施形態１とほぼ同じ効果が得られる。 (Embodiment 4)
7 showing the same parts as in FIG. 4 showing the second embodiment is a configuration showing the main part of the simplified configuration of the double-suction ventilating rotary electric machine of the fourth embodiment of the present invention, in particular, the convex-pole synchronous machine. FIG. The fourth embodiment differs from the second embodiment in that the stator ventilation duct 12 of FIG. 4 is extended to the outer peripheral portion so as to be parallel to the stator ventilation duct 7 near the center of the stator frame 17 as shown in FIG. The current plate 13 is provided between them. Therefore, the fourth embodiment has both the characteristics of the first embodiment and the third embodiment, and is an embodiment obtained by improving the third embodiment. In the third embodiment, the amount of ventilation is not completely uniform, but substantially the same effect as in the first embodiment can be obtained.

（実施形態５）
次に本発明を全閉内冷形回転電機に適用した実施形態５を、図１と同一部分に同一符号で示した図８に基いて説明する。回転電機の設置場所の条件により、回転電機の外部から冷却媒体を吸入し、冷却した後の媒体を外部に流出することが難しい場合には、全閉形回転電機が使用されるが、特に中型以上の回転電機では内部循環冷却媒体を冷却するために回転電機内部もしくは外部に冷却機または熱交換器を設けた全閉内冷形、全閉管通風形が使用される。 (Embodiment 5)
Next, a fifth embodiment in which the present invention is applied to a fully-closed internally cooled rotating electric machine will be described with reference to FIG. If it is difficult to draw the cooling medium from the outside of the rotating electrical machine and flow the cooled medium out to the outside due to the conditions of the location of the rotating electrical machine, a fully enclosed rotating electrical machine is used. In order to cool the internal circulation cooling medium, a fully closed internal cooling type and a fully closed pipe ventilation type in which a cooler or a heat exchanger is provided inside or outside the rotary electric machine are used.

図８は固定子通風ダクト１２に冷却機または熱交換器１９を設け、通風ダクト７の外周部に吐出した冷却媒体３をこの冷却機１９により冷却した後、連絡ダクトを経て吸気口２に導き吸入ファン１により再び回転子４及び固定子６に供給する。このように全閉内冷形回転電機では、機内連結ダクト１８の形状を図１の実施形態１のような形状とすることにより、通風抵抗を連続的とすることが可能となり、通風ダクト７を通過する冷却媒体が均一化され、その結果として吸入ファン１を小型することが可能となり、高効率の回転電機を提供することができる。 In FIG. 8, a cooling device or heat exchanger 19 is provided in the stator ventilation duct 12, and the cooling medium 3 discharged to the outer periphery of the ventilation duct 7 is cooled by the cooling device 19 and then led to the intake port 2 through the communication duct. The suction fan 1 supplies the rotor 4 and the stator 6 again. As described above, in the fully closed internal cold type rotating electrical machine, it is possible to make the ventilation resistance continuous by making the shape of the in-machine connection duct 18 as shown in Embodiment 1 of FIG. The cooling medium passing therethrough is made uniform. As a result, the suction fan 1 can be reduced in size, and a highly efficient rotating electrical machine can be provided.

なお、上記では本発明の実施形態の説明を凸極形同期機を例にして説明したが、本発明は凸極形同期機に限られることはなく、固定子と回転子とから構成され、ファンを具備した回転電機はその機種、容量、形式の如何にかかわらず適用できることは勿論である。 In the above description, the embodiment of the present invention has been described by taking a salient-pole synchronous machine as an example, but the present invention is not limited to a salient-pole synchronous machine, and includes a stator and a rotor. Needless to say, a rotating electrical machine equipped with a fan can be applied regardless of its model, capacity, and type.

本発明の実施形態１を示す構成図である。It is a block diagram which shows Embodiment 1 of this invention. 本発明の実施形態１の効果を説明するための固定子冷却媒体の通風量分布を示す曲線図である。It is a curve figure which shows the ventilation volume distribution of the stator cooling medium for demonstrating the effect of Embodiment 1 of this invention. 本発明の実施形態１の効果を説明するための固定子コイルの温度分布を示す曲線図である。It is a curve figure which shows the temperature distribution of the stator coil for demonstrating the effect of Embodiment 1 of this invention. 本発明の実施形態１の吸入ファンの動作点を説明するための曲線図である。It is a curve for demonstrating the operating point of the suction fan of Embodiment 1 of this invention. 本発明の実施形態２を示す構成図である。It is a block diagram which shows Embodiment 2 of this invention. 本発明の実施形態３を示す構成図である。It is a block diagram which shows Embodiment 3 of this invention. 本発明の実施形態３の効果を説明するための固定子冷却媒体の通風量分布を示す曲線図である。It is a curve diagram which shows the ventilation volume distribution of the stator cooling medium for demonstrating the effect of Embodiment 3 of this invention. 本発明の実施形態３の効果を説明するための固定子コイルの温度分布を示す曲線図である。It is a curve diagram which shows the temperature distribution of the stator coil for demonstrating the effect of Embodiment 3 of this invention. 本発明の実施形態４を示す構成図である。It is a block diagram which shows Embodiment 4 of this invention. 本発明の実施形態５を示す構成図である。It is a block diagram which shows Embodiment 5 of this invention. 従来の回転電機を説明するための構造図である。It is a structural diagram for explaining a conventional rotating electrical machine. 従来の回転電機の特性を説明するための固定子冷却媒体の通風量分布を示す曲線図である。It is a curve figure which shows the ventilation volume distribution of the stator cooling medium for demonstrating the characteristic of the conventional rotary electric machine. 従来の回転電機の特性を説明するための固定子コイルの温度分布を示す曲線図である。It is a curve figure which shows the temperature distribution of the stator coil for demonstrating the characteristic of the conventional rotary electric machine. 従来の回転電機を説明するための断面図である。It is sectional drawing for demonstrating the conventional rotary electric machine.

Explanation of symbols

１吸入ファン
２吸気口、２’排気口、
３冷却媒体、３−１冷却媒体、３−２冷却媒体、３−３冷却媒体、
４回転子、４−１回転子スパイダー、４−２回転子磁極、
５軸方向通風部、
６固定子、
７固定子通風ダクト、
８固定子コイル、
９固定子コイルエンド、
１０固定子通風ダクト押え、
１１シャフト、
１２固定子通風ダクト、
１３整流板、
１４固定子フレーム、
１５固定子フレーム、
１６排気ダクト、
１７固定子フレーム、
１８連結ダクト、
１９冷却機または熱交換器、
２０リブ、
２１金網。 1 intake fan 2 intake port, 2 'exhaust port,
3 Cooling medium, 3-1 Cooling medium, 3-2 Cooling medium, 3-3 Cooling medium,
4 Rotor, 4-1 Rotor Spider, 4-2 Rotor magnetic pole,
5 Axial ventilation section,
6 Stator,
7 Stator ventilation duct,
8 Stator coil,
9 Stator coil end,
10 Stator ventilation duct presser,
11 shaft,
12 Stator ventilation duct,
13 Current plate,
14 Stator frame,
15 Stator frame,
16 Exhaust duct,
17 Stator frame,
18 connecting ducts,
19 Coolers or heat exchangers,
20 ribs,
21 Wire mesh.

Claims

A stator, a rotor, an axial fan provided at both axial ends of the rotor, and a cooling medium sucked by the axial fan through the axial ventilation portion of the rotor; In a rotating electrical machine comprising a ventilation system that flows a cooling medium that has cooled the rotor by the self-ventilating centrifugal fan effect to the stator ventilation duct and discharges the cooling medium to the outer periphery of the stator ventilation duct , in the stator end proximate the stator, the stator central portion near a position spaced with the stator, and without providing the said stator central part, reduce the ventilation resistance of the stator central portion near By attaching an integrated stator ventilation duct presser that increases the ventilation resistance of the stator end , the ventilation resistance is continuously changed, and the flow rate of the cooling medium passing through the stator ventilation duct is uniform. In Stator rotary electric machine, characterized by cooling the coil.

In the rotating electrical machine according to claim 1, by extending the vicinity of the center portion of the stator ventilation duct presser to the outer peripheral side so as to be parallel to the stator ventilation duct, and providing one or more rectifying plates therebetween A rotating electrical machine characterized by further reducing ventilation resistance during exhaust.

The rotating electric machine according to claim 1, by cutting out the stator frame instead of the stator ventilation ducts pressing the central portion near the stator core, it has a substantially uniform amount of coolant that passes through the stator ventilation duct Rotating electric machine.

4. The rotating electric machine according to claim 3, wherein the stator frame is protruded from the outer peripheral portion of the stator core substantially at right angles to the axial direction, and one or a plurality of rectifying plates are provided therebetween to cool the stator frame through the stator ventilation duct. A rotating electric machine characterized by facilitating the flow of a medium.

The rotating electrical machine according to claim 1 or 4, wherein a ventilation duct is provided so that the cooling medium discharged to the outer peripheral side of the stator ventilation duct is sucked by an axial fan provided at both axial ends of the rotor, and the ventilation duct A structure that is suitable for a fully-closed type that aims to circulate the cooling medium inside by arranging a cooler or heat exchanger in the middle, to smooth the passage of the cooling medium and to optimize the flow rate of the cooling medium. A rotating electric machine that is characterized.