Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-05-09
2002-07-30
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C029S598000
Reexamination Certificate
active
06426578
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electric rotating machine which can be reduced in size by improving the thermal conductivity of an insulating material used therein.
A method of improving the thermal conductivity of a main insulator used in the stator windings of an electric rotating machine is described in, for example, an article entitled “An Improved Insulation System for the Newest Generation of Stator Windings of Rotating Machines”, CIGTE, 1994 Session, August 28-September 3, 11, 101. In the described method, the overall thermal resistance of the stator windings is reduced by filling the main insulation with fine particles made of an insulation material having a high thermal conductivity, such as alumina. Further, a main insulator formed by adding high thermally conductive particles or a composite of the particles and glass fiber into mica bonding layers is disclosed in Japanese Patent Application Laid-open No.63-110929 and Japanese Patent No. 127364 (1987). Furthermore, an insulation formed by bonding a tape made of mica and glass fiber cloth is disclosed in Japanese Patent No. 411834.
Although the thermal conductivity of a main insulator used in the stator windings of an electric rotating machine has been increased as described above, the overall thermal resistance of the main insulator of the stator windings can not be decreased when the heat load is increased as the electric power generating capacity increases. When the electric power generating capacity is increased, the voltage generated in the stator windings is generally increased and, consequently, the thickness of the main insulator must be increased in order to obtain a required electric insulating property. Particularly, in a case where the breakdown voltage per unit of thickness of the main insulator is low, the thickness of the main insulator increases. Therefore, when an attempt is made to increase the electric power generating capacity while keeping the size constant, the thickness of the main insulator has to be increased, and, accordingly, the machine size inevitably increases.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electric rotating machine which is small in size and low in cost by reducing the necessary thickness and volume of insulation through an adjustment of the breakdown voltage and thermal conductivity of an insulator and an insulation composing the other insulations. Further, another object of the present invention is to provide a method of measuring the thermal conductivity of an insulator under a condition in which the insulator is applied to an electric conductor.
An essential feature of the present invention is that a main insulator used in a stator winding of a rotary electric machine comprises a laminated layer composed of a first insulating layer formed by bonding a thin flake-shaped inorganic insulating material substantially excluding a granular filler with a thermosetting resin and a second insulating layer formed by dispersing a fiber insulating material and a high thermally conductive filler into a resin and curing the resin, wherein the initial breakdown voltage V is set to a value higher than 20 kV/mm, and the thermal conductivity &lgr; in a thickness direction of the laminated layer is within a range of 0.35 to 1 W/m·K, preferably 0.5 to 1 W/m·K, and the product V·&lgr; of the initial breakdown voltage and the thermal conductivity is set so as to satisfy the relationship of 7≦V&lgr;≦20 (MVW/m
2
·K). In order to obtain the above-described thermal conductivity &lgr;, an insulation satisfying the value V&lgr; described above is formed by filling or mixing a granular insulating material having a high thermal conductivity higher than 5 W/m·K into a resin together with a fiber cloth.
The first insulation layer is formed by bonding a flake-shaped insulating material, such as mica, having a high electric insulating property capable of ensuring a high dielectric strength, with a thermosetting resin. A granular hard insulating material is not added in the first insulation layer so that the insulating material flakes are aligned and bonded in a layer shape and so as to prevent the flake-shaped insulating material from being broken. This point is based on an idea completely different from the prior art described above.
The second insulation layer contains a fiber cloth, such as a glass fiber, or a plastic tape, such as a polyimido film. The fiber cloth is necessary for increasing the mechanical strength of the insulating material layer and for forming the composite laminated body composing the main insulation into a tape. Either woven cloth or unwoven cloth may be employed as the cloth. The granular high thermally conductive insulating material is indispensable for increasing the thermal conductivity of the main insulation tape, and a material having a thermal conductivity higher than 5 W/m·K, particularly, higher than 30 W/m·K, is employed as the granular high thermally conductive insulating material. The cloth and the granular or flaky filler are mixed in a thermosetting resin, and the resin is cured.
One or more of the first insulation layer and the second insulation layer are employed alternatively. An amount of the resin is selected so that the thermal conductivity in the thickness direction of the laminated body attains a value higher than 0.3 W/m·K, particularly within a range of 0.35 to 1 W/m·K, preferably within a range of 0.5 to 1 W/m·K. The initial breakdown voltage of the laminated body depends on the amount of the resin being used. When the amount of resin is too small, the initial breakdown voltage of the insulation tape becomes insufficient. When the amount of resin is too large, the thermal conductivity of the insulation tape becomes insufficient. The amount of the resin in the insulation tape is preferably within a range of 20 to 50 weight %.
The insulation used for the second insulation layer may be used as a spacer insulation. The amount of the resin and the amount of the filler are adjusted so that the thermal conductivity of the second insulation layer becomes within the range of 0.35 to 1 W/m·K, and the initial breakdown voltage becomes higher than 20 kV.
The amount of insulating material added in the resin is adjusted so that the above-mentioned value V&lgr; is satisfied, the necessary thermal conductivity is obtained, and the breakdown voltage is not decreased. In the case of a rotary electric machine in which the inside of the rotary electric machine is cooled by hydrogen when the value V&lgr; of the stator windings using the main insulation set within the above-mentioned range is used in the electric rotating machine, a ratio of a product of the diameter of the rotor squared and the shaft length of the stator to the electric generating capacity per number of rotations becomes smaller than 40 m
3
·rpm/MVA, and the ratio of a product of the diameter of the rotor squared and the length between supports of the rotor to the electric generating capacity per number of rotations becomes smaller than 50 m
3
·rpm/MVA. In the case of an electric rotating machine in which the inside of the electric rotating machine is cooled by air, the ratio of the product of the diameter of the rotor squared and the shaft length of the stator to the electric generating capacity per number of rotations becomes smaller than 70 m
3
·rpm/MVA, and the ratio of the product of the diameter of the rotor squared and the length between supports of the rotor to the electric generating capacity per number of rotations becomes smaller than 85 m
3
·rpm/MVA.
Further, the present invention improves the thermal conductivity of a rotating electric machine by filling or mixing insulating materials having a thermal conductivity higher than 5 W/m·K into insulators in the rotor, such as a slot insulator, an insulating block or a retaining insulator, or spacers interposed between windings at an end portion of the stator winding. Furthermore, the present invention can be applied to a conductor sheathed with an insulating tape containing a wov
Amagi Shigeo
Mori Hideaki
Onoda Mitsuru
Sonobe Tadashi
Tsunoda Tomoya
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Waks Joseph
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