Analysis of Insulation Structure of High Voltage Large and Medium Motors
2022-12-05
1. Armature insulation structure of DC motor
Armature insulation structure of DC motor is composed of winding insulation, commutator insulation, support insulation, wire tie insulation and interlayer insulation. Due to the different types, voltage levels and binding materials of armature windings, the insulation structure of armature varies in some places.
1.1 Armature winding insulation Armature winding insulation structure varies with different winding structure types. In order to improve the moistureproof performance, the armature windings of large DC motors generally adopt continuous insulation.
1.1.1 Turn to turn insulation is used to insulate adjacent components in the same coil and only bear inter chip voltage. The turn to turn insulation of large DC motors generally adopts a half lapped layer of 0.1mm mica tape outside the bare copper wire, or directly adopts high-strength enamelled double glass wire. Small and medium-sized motors generally use double glass fiber wrapped wire. For Class F film insulated large motors, 0.05mm thin films can be semi laminated and sintered on the conductor, or a layer of glass ribbon can be added. The medium and small motors are semi overlapped with a layer of 0.05mm film or the film is "sintered" on the conductor.
1.1.2 Main insulation for ground insulation shall bear the full voltage between coil and iron core. 1000V large motor: 0.14mm alkyd mica tape is half lapped in three layers. 660 volt grade medium motor: 0.14 mm alkyd mica tape half lapped with two layers (continuous insulation) or 0.2 mm mica foil wrapped with two layers (sleeve insulation). Class F film large motor: 0.05mm polyimide film half lapped with four layers. Medium and small class F or class H motors: 0.05mm polyimide film half lapped with 2-3 layers.
1.1.3 The protective cloth tape mainly protects the main insulation from mechanical damage. Generally, Class B insulated motor adopts a half lapped or flat wound layer of 0.1mm glass ribbon. Class F film insulation generally does not need protective cloth tape. Sometimes, for the sake of reliability, 0.1mm glass ribbon is also used for half lapping.
1.1.4 The insulation method and material of the armature winding end are generally the same as those of the straight part, except that the insulation to the ground can be wrapped 1-2 layers less than the straight part. Although full voltage exists at the end to ground and between layers, it is mainly due to the existence of interlayer insulation and support insulation, and also to improve cooling conditions. Therefore, the insulation at the end of winding should be properly reduced during manufacturing.
1.2 Protective insulation of coil in slot
1.2.1 The slot insulation shall prevent the coil from being scratched by the burr in the slot or the sharp edge of the slot. Class B insulation: 0.2mm polyester film yellow glass varnished cloth composite insulation, 0.2mm polyester film green shell paper composite insulation, or 0.2mm green shell paper instead. Class F film insulation: 0.15 mm polyimide yellow glass paint cloth or 0.1 mm polyimide paint cloth.
1.2.2 The slot bottom spacer strip and interlayer spacer strip shall protect the winding from mechanical damage during winding winding. Class B insulation adopts 0.5mm alkyd soft mica plate. Class F insulation adopts diphenyl ether glass cloth board or silicone organic mica board.
1.3 The fixed insulation structure at the end of armature coil is illustrated by taking the four layer frog winding with ventilation hole in the middle of the end as an example:
1.3.1 Support insulation Large motor Class B insulation, generally the innermost layer is half wrapped with 0.1mm glass ribbon, the outer layer is half wrapped with 0.14mm alkyd mica tape, the outer layer is wrapped with two layers of 0.3mm soft mica plate, and the outer layer is half wrapped with 0.03mm polyester film tape and 0.1mm glass ribbon respectively. Class F insulation generally uses silicone organic mica tape and mica plate to replace alkyd mica tape.
1.3.2 The end interlayer insulation bears the full voltage between layers of coils and protects coils from mutual crushing. Class B insulation is generally made of two layers of 0.5mm cushion mica plate, and is wrapped with 0.1mm glass fiber cloth to avoid flying during operation. Class F insulation is generally made of silicon organic mica plate or Class F film.
1.3.3 The steel wire shall be bound to insulate the steel wire from the winding and protect the winding from being scratched by the steel wire. Close to the winding, a layer of 0.6mm yellow insulating cardboard shall be wound first, two layers of 0.5mm cushion mica board shall be wound outside (wrapped with glass fiber cloth), and a layer of 1mm yellow insulating cardboard shall be wound outside, and each layer shall be fastened with glass fiber tape. To prevent creepage, the insulation of steel wire shall be 8-15mm wider than each side of steel wire hoop. To limit the eddy current loss in the steel hoop, a layer of 0.2mm asbestos paper shall be placed between every 10 turns of steel wire to isolate them from each other. For Class F insulation with steel wire, diphenyl ether glass cloth board and silicone organic mica board are used. If weft free tape is used to bind the ends, no insulation is needed.
1.3.4 Commutator insulation structure Commutator mica plays the role of inter sheet insulation and increasing commutator elasticity in the commutator. It is required that the rubber content is small. Generally, 1.0mm or 1.1mm commutator mica plate 5531 is used. Silicone organic mica board is used for Class F insulation. The V-ring bears the voltage to the ground in the commutator, and bears the tightening force of the pressure ring on the commutator. It is generally formed by hot pressing 5238 shellac mica plate, with a thickness of 2 mm at 1000 volts. Class F insulation is silicon organic mica plate. In order to prevent dust from entering the 3 ° face of the commutator, the commutator is coated and sealed with epoxy phenolic paint and 1053 silicon organic resin for Class F insulation. In order to prevent the exposed part of the V-ring from flying away during operation, the V-ring shall be tied with glass fiber rope, glass fiber belt or weft free glass fiber belt.
1.3.5 Overall insulation treatment of armature After winding down, the armature shall be dipped with 1032 or 3404 paint for three times to improve moisture resistance, and the surface shall be sprayed with 1321 or 8363 gray enamel paint to improve ash, oil and mold resistance.
1.4 Pole insulation of main pole insulation structure of DC motor: withstand the voltage of main pole coil to ground.
1.4.1 Molded electrode body insulation is made of epoxy phenolic glass cloth by hot pressing, with a thickness of 4mm.
1.4.2 Wrap two layers of 0.1mm glass fiber cloth, then wrap five layers of 0.2mm alkyd mica foil outside, and wrap two layers of 0.1mm glass fiber cloth around the outermost layer. Epoxy phenolic paint shall be applied between layers, and each layer shall be ironed with an electric iron.
1.4.3 Compensation winding insulation to ground insulation 0.14mm mica tape is half lapped for three layers, and 0.1mm glass fiber tape is half lapped for one layer (or 0.17 * 25B grade adhesive mica tape 5438 is half lapped for four layers, and hot pressed). One layer of 0.2 mm polyester film glass cloth composite insulation for tank insulation, and one layer of 0.5 mm epoxy phenolic glass cloth for tank bottom cushion strip.
1.4.4 The main pole winding is a single-layer main pole winding with insulation. Four layers of 0.1mm epoxy phenolic glass cloth are padded between turns and hot pressed. The first and last two turns are wrapped with 0.14mm mica tape and 0.1mm glass ribbon respectively. Multilayer main pole winding, high strength enamelled double glass fiber wrapped wire or double glass fiber wrapped wire for turn to turn insulation. A layer of 0.1mm glass ribbon is half lapped outside for protection and insulation, and it is dipped in 3404 paint once. Series winding (equalizing winding): 0.14mm mica tape is half lapped in three layers, 0.1mm glass ribbon is half lapped in one layer, and is dipped in 3404 paint (1kV grade). Insulating washer, 3240 epoxy sheet, painted with 3404 paint. The thickness depends on the creepage distance. Overall insulation treatment of main pole: soak 3404 paint once to increase thermal conductivity and moisture resistance.
1.5 Commutating pole insulation structure Commutating pole winding can be fixed in different forms due to different motor capacity and use, and its insulation structure is also slightly different. The commutating pole winding is generally wrapped with copper wire, without interlayer insulation. The pole body insulation is completely the same as the main pole body wrapping. There are two types of screw insulation: one is to use epoxy phenolic glass cloth pipe with wall thickness of 1.0~2.0 mm as screw insulation, the other is to wrap 0.1 mm epoxy phenolic glass cloth on the screw for hot pressing. The insulating cushion block and triangular cushion block are 3240 epoxy phenolic glass cloth board. Clamp insulation: three layers of 0.14mm mica tape and one layer of 0.1mm glass ribbon are semi overlapped for the commutation pole winding at the clamp, and the width of each side is 50mm larger than that of the clamp. Fixing clip insulation: two layers of 0.3mm soft mica board (inside), two layers of 0.2mm insulating cardboard (outside), width greater than 12.5mm on each side of the fixing clip Φ L The glass wire rope shall be fastened.
1.6 Insulation of other parts of DC motor
1.6.1 Armature punching insulation Class B insulation brush 1611 silicon steel sheet paint. Class H insulation brush 1053 silicon organic paint.
1.6.2 Grade B insulation of armature, main pole and reversing pole tension screw is generally continuously wrapped with 5438B rubber mica tape and formed by hot pressing. Continuous wrapping of film tape for grade F
2. Stator insulation of high-voltage AC motor
2.1 Stator insulation structure of high-voltage AC motor: due to different voltage grades, insulation materials and motor capacities, it has a great impact on the operation reliability. There are many kinds of stator insulation structures. The AC high-voltage motor has three voltage levels: 3000 V, 6000 V and 10000 V (10500 V). There are three insulation grades: A, B and F. At present, Class A insulated stator windings have been eliminated, and Class B and Class F insulation are widely used. Due to the different process habits, process equipment and sources of insulation materials of various manufacturers, there are basically three types of B class insulation high-voltage stator insulation structures: composite insulation structures. The linear part is formed by hot pressing 5438B grade rubber mica tape, and the end part is continuously semi overlapped with yellow glass paint cloth tape (or asphalt mica tape, self-adhesive silicone rubber tape, etc.). The reason is that Class B rubber insulation has poor elasticity after curing, it is difficult to embed wires, and the end is vulnerable to mechanical damage, so other insulation materials are used at the end. However, the end of composite insulation structure has poor electrical strength and moisture resistance. At present, most domestic manufacturers also adopt composite structure. Soft downline structure of all mica ends. The insulation of the whole coil to the ground is made of Class B rubber mica tape. The straight part is hot pressed and the end is not solidified. It is wrapped with a layer of heat shrinkable resin tape. The soft downline is applied. After the downline, both ends are dipped in paint. The whole mica powder is immersed in paint insulation structure. The linear part and end of the coil are insulated to the ground with mica tape. The coil is directly wound without curing, and the stator is overall dipped with paint after winding. At present, all high-voltage AC motors produced abroad (America, Germany, Japan, etc.) are of Class F.
2.2 The turn to turn insulation of high-voltage AC motor is 3 kV: generally, double glass wire and three glass wire are used, a layer of mica tape is padded between layers, and epoxy phenolic paint is applied for hot pressing. 6 kV grade: double glass fiber wrapped, double glass fiber wrapped high strength enamelled wire is used, the outer half is wrapped with a layer of mica tape, and is brushed with epoxy phenolic paint for hot pressing. 10kV grade: one more layer of mica tape than 6kV grade.
2.3 The insulation structure and insulation treatment method of stator to ground insulation are different due to different insulation processes, insulation materials and voltage levels.
2.4 The insulation materials and treatment methods of pole body insulation, turn to turn insulation and insulation gasket of synchronous machine pole winding insulation are identical with that of DC motor main pole insulation.
3. Motor insulation trend
Due to the progress of materials and technology, the insulation of high-voltage AC motors in China has been made of epoxy based impregnating varnish flat grade B rubber mica tape with thermoelastic insulation (the so-called thermoelastic insulation refers to making the thermal expansion coefficient of the insulation structure almost equal to the thermal expansion coefficient of copper, so that the insulation edge expands and contracts with copper, and the insulation structure can always adhere to the surface of the copper wire without relative displacement, so there is no gap). It has completely replaced the previous grade A insulation structure of asphalt glue+biotite tape, and is developing towards integral impregnation of stator. This not only improves the insulation grade and electrical strength of insulation, but also reduces the motor volume, saves large mica materials, and further improves the insulation reliability.
The development trend of DC motor insulation is to improve the insulation grade and make the insulation film. The measures are: firstly, aromatic and heterocyclic resin fibers and films (such as polyamide, polyimide, polyamide imide, etc.) are used as the motor turn to turn insulation and main insulation. Secondly, heat-resistant impregnating varnish (such as diphenyl ether and modified silicone organic paint) is used. These aromatic and heterocyclic films have the advantages of high electrical strength, high temperature resistance, good strength, corrosion resistance and radiation resistance,
Not only can the insulation grade be improved to F and H (the film material itself is H insulation, which is generally made to F because of the easy solution of impregnating varnish, heating furnace and other supporting materials in the manufacture of large DC motors), but also the insulation thickness is greatly reduced and the motor volume is reduced. Therefore, the technical indicators and performance of the motor are greatly improved.
Many factories have done a lot of work in replacing the original Class B insulation with Class H film, with remarkable results and some experience. At present, domestic motor manufacturers have begun to trial produce large motors with F grade film insulation.
