1. Armature insulation structure of DC motors
The armature insulation structure of a DC motor is composed of winding insulation, commutator insulation, bracket insulation, wire tie insulation, and interlayer insulation. Due to the different types of armature windings, voltage levels, and binding materials used, the insulation structure of the armature may vary in some areas. 
1.1 Armature winding insulation The insulation structure of the armature winding varies with the type of winding structure. In order to improve moisture-proof performance, the armature winding of large DC motors generally adopts continuous insulation. 
1.1.1 Interturn insulation refers to the insulation of adjacent components within the same coil, only withstanding inter chip voltage. Large DC motors usually use bare copper wire with a layer of 0.1mm mica tape wrapped on the outer half, or directly use high-strength enameled double glass fiber wrapped wire for inter turn insulation. Small and medium-sized motors generally use double glass wire wrapping. In F-class thin film insulated large motors, a 0.05mm thin film can be semi laminated and "sintered" onto the conductor, or a layer of glass ribbon can be added. Small and medium-sized motors are semi laminated with a layer of 0.05mm thin film or "sintered" onto the conductor. 
1.1.2 Main insulation to ground, withstand the full voltage between the coil and the iron core. 1000 volt class large motor: 0.14mm alkyd mica tape semi laminated with three layers. 660 volt grade medium-sized motors: 0.14mm alkyd mica tape semi laminated with two layers (continuous insulation) or 0.2mm mica foil wrapped with two layers (sleeve insulation). Class F film large motor: 0.05mm polyimide film half lapped four layers. Medium and small class F or class H motors: 0.05mm polyimide film half lapped with 2-3 layers. 
1.1.3 Protective tape mainly protects the main insulation from mechanical damage. Generally, Class B insulated motors use 0.1mm glass ribbon with half stacked or flat winding in one layer. Class F thin film insulation generally does not require protective tape, and sometimes, for reliability reasons, 0.1mm glass fiber tape is used as a half layered layer. 
1.1.4 The insulation method and material at the end of the armature winding are generally the same as those of the straight part, except that the insulation to ground can be reduced by 1-2 layers compared to the straight part. Although there is full voltage at the end to ground and between layers, it is mainly due to the presence of interlayer insulation and bracket insulation, and also to improve cooling conditions, so the manufacturing of winding end insulation is appropriately reduced. 
1.2 Protective insulation of the coil in the slot
1.2.1 Slot insulation prevents burrs or sharp edges inside the slot from scratching the coil. Class B insulation: 0.2mm polyester film yellow glass coated cloth composite insulation, 0.2mm polyester film green shell paper composite insulation, or use 0.2mm green shell paper as a substitute. Class F film insulation: 0.15mm polyimide yellow glass varnished cloth or 0.1mm polyimide varnished cloth. 
1.2.2 The slot bottom gasket and interlayer gasket protect the winding from mechanical damage during the winding process. Class B insulation uses 0.5mm alkyd soft cloud motherboard. Class F insulation adopts diphenyl ether glass cloth board or silicone organic mica board. 
1.3 The fixed insulation structure at the end of the armature coil is illustrated by using a four layer frog winding with ventilation holes in the middle of the end as an example:
1.3.1 Bracket insulation: Large motor B-level insulation, usually with a 0.1mm glass fiber tape half wrapped in one layer on the innermost layer, and a 0.14mm alkyd mica tape half wrapped in three layers on the outer layer. The outer layer is surrounded by a 0.3mm soft mica plate in two layers, and the outer layer is half wrapped with a 0.03mm polyester film tape and a 0.1mm glass fiber tape, each layer. F-grade insulation generally uses silicone organic mica tape and mica plate instead of alkyd mica tape. 
1.3.2 The interlayer insulation at the end bears the full voltage between the coil layers and protects the coil from mutual pressure damage. Class B insulation generally uses two layers of 0.5mm padded mica board and is wrapped with 0.1mm glass fiber cloth to avoid flying during operation. F-grade insulation generally uses silicon organic mica board or F-grade thin film. 
1.3.3 Tie the steel wire to isolate the steel wire from the winding and protect the winding from wire damage. Close to the winding, first wrap one layer of 0.6mm yellow insulating cardboard, and then wrap two layers of 0.5mm lined mica board (wrapped with glass fiber cloth) on the outside. Wrap one layer of 1mm yellow insulating cardboard on the outermost side, and tie each layer tightly with glass fiber tape. To prevent creepage, the insulation of the steel wire is 8-15 millimeters wider on each side than the steel wire clamp. To limit eddy current loss in the steel wire hoop, a layer of 0.2mm asbestos paper should be placed between every 10 turns of steel wire to isolate them from each other. F grade insulation with steel wire insulation uses diphenyl ether glass cloth board and silicone organic mica board. If the end is tied with a weft free tape, no insulation is required. 
1.3.4 Commutator insulation structure: Commutator mica plays a role in interlayer insulation and increasing the elasticity of the commutator, and requires a small adhesive content. Generally, 1.0mm or 1.1mm commutator mica plate 5531 is used. For Class F insulation, silicon organic mica board is used. The V-shaped ring bears the voltage to ground in the commutator and the tightening force of the compression ring on the commutator. It is generally formed by hot pressing of 5238 shellac motherboard, with a thickness of 2 millimeters in the 1000 volt level. Class F insulation is made of silicon organic mica board. In order to prevent dust from entering the 3 ° surface of the commutator, the commutator has been coated with epoxy phenolic paint as the sealing material, and 1053 silicone organic resin is used for Class F insulation. To prevent the exposed part of the V-ring from flying during operation, tie glass wire rope, glass wire tape, or weft free glass wire tape onto the V-ring. 
1.3.5 Overall insulation treatment of the armature. After the armature is taken offline, it is immersed in 1032 or 3404 paint three times to improve moisture resistance, and the surface is sprayed with 1321 or 8363 gray enamel paint to improve ash, oil, and mold resistance. 
1.4 Insulation structure of the main pole of a DC motor: Pole body insulation: withstand the voltage of the main pole coil to ground. 
1.4.1 Formed pole body insulation, made of epoxy phenolic glass cloth by hot pressing, with a thickness of 4mm. 
1.4.2 Wrap 2 layers of 0.1mm glass fiber cloth, then 5 layers of 0.2mm alkyd mica foil on the outside, and 2 layers of 0.1mm glass fiber cloth on the outermost layer. Epoxy phenolic paint is applied between layers, and each layer is ironed flat with an electric iron. 
1.4.3 Compensation winding insulation to ground insulation: 0.14mm mica tape is half wrapped in three layers, and 0.1mm glass fiber tape is half wrapped in one layer (or 0.17 * 25B grade mica tape 5438 is half wrapped in four layers and hot pressed). One layer of 0.2mm polyester film glass coated cloth composite insulation for slot insulation, and one layer of 0.5mm epoxy phenolic glass cloth plate for slot bottom gasket. 
1.4.4 Single layer main pole winding insulation, with four layers of 0.1mm epoxy phenolic glass cloth padded between turns, hot pressed, and the first and last two turns wrapped with 0.14mm mica tape and 0.1mm glass fiber tape. Multi layer main pole winding, with high-strength enameled double glass fiber wrapped wire or double glass fiber wrapped wire for inter turn insulation. Wrap a layer of 0.1mm glass ribbon on the outside for protective insulation and soak it in 3404 paint once. Series winding (balanced winding): 0.14mm mica tape half stacked in three layers, 0.1mm glass fiber tape half stacked in one layer, and dipped in 3404 paint (1 kV level). Insulating gasket, 3240 epoxy phenolic glass cloth board, painted with 3404 paint. The thickness depends on the creepage distance. Overall insulation treatment of the main pole: Dip 3404 paint once to increase thermal conductivity and moisture resistance. 
The insulation structure of the 1.5 commutation pole The fixed form of the commutation pole winding varies depending on the motor capacity and purpose, and its insulation structure also varies slightly. The commutation pole winding is generally wrapped in copper wire winding without interlayer insulation. The insulation of the pole body and the wrapping method of the main pole body are completely the same. There are two types of screw insulation: one is to use epoxy phenolic glass cloth pipes with a wall thickness of 1.0-2.0mm as screw insulation, and the other is to wrap 0.1mm epoxy phenolic glass cloth on the screw for hot pressing forming. The insulation pad and triangular pad are both 3240 epoxy phenolic glass cloth sheets. Insulation of wire clamp: The commutation pole winding at the wire clamp is wrapped in three layers of 0.14mm mica tape and one layer of 0.1mm glass fiber tape, with a width of 50mm greater than each side of the wire clamp. Fixed clamp insulation: Two layers of 0.3mm soft mica board (inside) and two layers of 0.2mm insulating cardboard (outside), with a width greater than 12.5mm on each side of the fixed clamp and a diameter of Φ Tie the glass wire rope tightly. 1.6 Insulation of other parts of DC motors