What aspects does motor insulation include?

Motor insulation includes the insulation between strands, turns, rows, layers and to ground of the coil, various insulating components used for various supports or fixations at the ends, and the insulation of connecting wires and lead wires.

What is the primary insulation of the coil?

The main insulation of the coil refers to the insulation between the coil and the fuselage and other windings, which is also commonly called ground insulation.

When is the inter-turn insulation?

Turn-to-turn insulation refers to the insulation between turns of the same coil.

How are laminated products made?

Laminated products are insulating materials with a layered structure made of fiber products, which are impregnated or coated with different adhesives to form fiber products and then hot pressed or rolled. They mainly include laminated boards, tubes (tubes), rods and special profiles.

What are the commonly used paint tubes?

Commonly used paint tubes include 2751 silicone rubber glass paint tube (H-grade insulation) and 2750 silicone glass paint tube (H-grade insulation).

What materials are insulating paint tubes made of? What is their main function?

The insulating varnish tube is made of natural fibers, synthetic fibers or alkali-free glass fibers woven into a tube, then impregnated with insulating varnish or resin, and dried to form a soft varnish tube with certain electromechanical properties. It is mainly used for the insulation of the lead-out wires of low-voltage coils or windings and the inter-pole connecting wires.

What types of glass varnished cloth are commonly used for coil insulation?

Four types of glass cloth are commonly used for coil insulation, namely: 2430 asphalt alkyd glass cloth, 2432 alkyd glass varnished cloth, 241 polyester glass varnished cloth, and 2450 silicone glass varnished cloth.

What are the advantages and disadvantages of glass fiber? What methods are commonly used to improve its disadvantages?

Advantages: strong tensile strength, high heat resistance, low moisture absorption. Disadvantages: poor softness, not folding resistance, often interlaced with synthetic fibers or chemically treated to improve its softness and adhesion of the paint film.

What are impregnated fiber products made of?

Fiber products made of insulating fiber products as the base material and impregnated with insulating varnish, such as varnished cloth, varnished tubes and binding tapes.

What are the two types of epoxy resin curing agents based on curing temperature?

Room temperature curing agent and heat curing agent.

What are the two types of epoxy resins commonly used for coil insulation?

Commonly used epoxy resins are bisphenol A and novolac epoxy resins.

What are the basic principles for selecting insulating covering paint?

①It has a fixed color, and the paint film is smooth, flat, bright and shiny.

②High dispersibility. Strong covering power. ③Long storage period, good stability, no agglomeration.

④The paint film has sufficient hardness and wear resistance and good mechanical properties.

⑤ The paint film has good arc resistance and dielectric properties. ⑥ The paint film has good moisture resistance, oil resistance, and chemical corrosion resistance. For the insulation covering paint for warm and hot zone motors, it should also have anti-toxicity and anti-salt spray properties.

⑦ For the special anti-corona covering paint used for high-voltage motors, it also has good resistance stability, uniformity and a certain resistance value. 

What are the basic principles for selecting insulating impregnating varnish?

① The viscosity should be low and the solid content should be high to facilitate penetration and filling of the impregnated object. The amount of paint should be large.

②The thick layer of impregnating paint cures quickly, dries well, has strong adhesion, the paint film is elastic, and can withstand the centrifugal force when the motor is running.

③It has good electrical properties, good heat resistance, moisture resistance, oil resistance and chemical resistance.

④It is harmless to conductors and other insulating materials and has good compatibility.

⑤ The price is low, the materials are based in China, the storage period is long and the toxicity is low.

What are the two types of insulating varnishes? What are their advantages and disadvantages?

Insulating varnishes can be divided into two types:

①Solvent-containing insulating impregnating varnish.

②Solvent-free insulating impregnating varnish.

The former has good permeability, long storage period, low price, convenient use and production management, but the paint has the disadvantages of long baking time and slow curing when dipping the workpiece, and the volatilization of the solvent causes waste and pollutes the environment. The latter has the advantages of fast curing, large viscosity change with temperature, small volatile matter during curing, good insulation and dielectric properties, and large paint hanging amount, but the paint has the disadvantages of high price, short storage period, high viscosity, and complex production management.

How many categories can insulating paint be divided into according to its use?

Insulating varnishes can be divided into impregnating varnishes, covering varnishes, flake varnishes, wire varnishes, adhesive varnishes, etc. according to their uses.

What are the two types of wire embedding for wound rotor windings? What kind of motors are they suitable for?

There are two types of winding for wound rotors: loose-embedded and inserted. The former is used for small motors, and the latter is used for medium and large motors.

What types of permanent magnet synchronous motor hidden pole rotor coils are there?

The hidden pole rotor coils of permanent magnet synchronous motors are of continuous, half-turn and single-layer concentric types.

What are the two structural forms of synchronous motor salient pole rotor coils?

There are two structures of synchronous machine salient pole rotor coils, namely multi-layer multi-turn pole coils and single-layer multi-turn pole coils.

What three materials are usually used to make the main insulation of the stator coil of a high-voltage motor? What are the main improvements to the main insulation?

The main insulation is usually composed of three materials: mica, reinforcement material and adhesive. The improvement of the main insulation mainly improves the heat resistance of the adhesive and the performance of the motor.

What insulation does the high-voltage motor ring stator coil insulation structure mainly determine?

What is a high voltage motor?

High voltage motors generally refer to AC motors and generators of 3KV and above.

What determines the stator slot shape of small and medium-sized motors? What slot shape do small low-voltage motors generally use?

The stator slot shape of small and medium-sized motors depends on the capacity, voltage and winding form. Small low-voltage motors generally use semi-closed slots.

What are the main factors that determine the insulation structure of low-voltage motors?

The main factors are groove shape, wire embedding method, insulation material and insulation treatment process.

What are the general heat resistance grades for motor winding insulation?

Motor winding insulation can be roughly divided into: Class B, Class F, Class H, and Class C.

Why do people compare the coil to the heart of the motor?

The insulation structure of the motor plays an insulating role, but some of them also play a role in mechanical support and fixation. During long-term operation, the insulation of the motor is affected by electrical, thermal, and mechanical forces and different environmental conditions. The insulation will gradually age and eventually lose its proper performance, resulting in insulation breakdown and inability to continue to operate safely. Therefore, the reliability and life of the motor operation are largely determined by the insulation of the coil, so people compare the coil to the heart of the motor.

What is inter-row insulation?

Inter-row insulation is the insulation of several rows of wires connected in parallel.

When is inter-femoral insulation?

Interstrand insulation refers to the insulation between the strands in the same turn, generally the insulation of the winding electromagnetic wire itself.

What is the basic dielectric barrier of mica products?

It's mica.

What properties does mica have?

Mica has good insulating dielectric properties, high heat resistance and chemical stability.

What are the three types of powdered mica paper that is currently widely used, based on their different preparation processes?

① Cooked powder mica paper, which is produced from mica scraps by thermochemical method.

② Raw powder mica paper, which is produced by using mica crushed materials and applying high-pressure water crushing method.

③ Large-scale mica paper, which is pure mica material, is a large-scale powder mica paper produced by high-pressure water impact method.

What are the advantages of powdered mica paper compared with mica flakes?

It has the following advantages:

① Improve the utilization rate of natural mica from the original 7%-10% to more than 80%.

② The thickness of the mica paper is uniform, and the thickness of the finished products is uniform, so the electrical properties are stable and the thermal conductivity is good.

③ It is conducive to the mechanized production of mica powder products, which can improve production efficiency, reduce costs and improve working conditions.

What are mica products mainly composed of?

It is mainly composed of mica, adhesive and reinforcing materials.

There are many varieties of mica products. How can they be classified according to their uses?

According to the use, it can be divided into four categories: mica tape, mica board, mica box and mica glass.

What kinds of electrical films are commonly used for coil insulation? Briefly describe their similarities? What are their uses?

Commonly used electrical films include: 6062 polyester film; 6065 polyesterimide film and polytetrafluoroethylene film. Their common features are thin thickness, softness, moisture resistance, and good electromechanical properties. Application: Mainly used as coil wrapping insulation, slot insulation of low-voltage motors, etc., and polytetrafluoroethylene film is often used as a demoulding material for coil insulation hot pressing molding.

Briefly describe the composition and purpose of composite products?

Composite products are insulating materials made by bonding fiber materials on one or both sides of electrical films. The purpose is to enhance the mechanical properties of the film, increase the tear strength and surface stiffness to improve the processability.

What are the commonly used composite products?

Commonly used composite products are:

①6520 polyester film insulation paper composite foil.

②6530 polyester film glass varnish cloth composite foil.

③ Polyester film, polyester fiber paper composite foil (DMD). ④ Polyester film, aromatic polyamide fiber paper composite foil (NMN).

⑤Polyester film sulfoneamide polyester non-woven fabric composite foil (SDMSD277).

⑥Polyimide film aromatic cluster polyamide fiber paper composite foil (NHN).

What are the four aspects that the inspection items of insulating materials can be divided into according to their performance?

According to its performance, it can be divided into four aspects: electrical, mechanical, physical and chemical, and thermal performance.

What are the main contents of testing the electrical properties of insulating materials?

The main items include: breakdown strength, volume resistivity, surface resistivity, relative dielectric constant, dielectric loss tangent and corona resistance.

Write out the three basic calculation formulas for determining the content of components in mica products? And mark the meaning of the letters in each formula?

① Volatile matter content X (%) X = (G-G1)/Gx100%;

② Adhesive content Y (%) Y = (G1-G2)/G1x100%;

③ Mica content Z (%) Z = 100% - (Y + KxKxFxD) / G1x100%;

Where:

G——sample weight before drying (g)  

G1——weight of sample after drying (g)

G2——weight of sample after burning (g)

K——Glass cloth standard weight (g/m²)

F——Sample area (m²)

D——Number of reinforcement layers.

Briefly describe the two appearance inspection methods of insulating paint?

Test tube method: Pour the paint into a dry, clean, colorless glass test tube with a diameter of 15 mm and leave it in an environment until the bubbles disappear; observe the color of the paint under diffuse light in daylight to see if it is transparent.

Smear method: Take two pieces of paint film samples before measuring the electrical properties to observe the color, gloss, presence of mechanical impurities and particles of the paint film.

What are the basic technical requirements for high voltage motor stator coils?

The number of turns is accurate and the insulation between turns is good. The insulation to the ground is good. The size and shape of the coil meet the requirements. The main insulation should have good wire embedding process performance. Meet other special requirements, such as explosion-proof, moisture-proof and mildew-proof, etc.

What are the common arrangements of turns of coil-type high-voltage stator coils?

The arrangement forms include single-wire winding, double-row winding of several wires, single-row winding of several wires, bow-shaped transposition, N-shaped transposition, brick-shaped arrangement, etc.

What types of inter-turn structures are there for coil-type high-voltage stator coils?

Common types include:

① Use winding wire insulation as turn-to-turn insulation.

② Place gold film pads between turns.

③Wrap the nose or the entire coil with a layer of mica tape every other half turn. ④Wrap 1 to 2 layers of mica tape per half turn.

⑤ An insulating tube is put on the transposition part of the bow-shaped transposition coil, and a soft mica board is padded at the intersection of the turns and the nose of the N-shaped transposition coil with insulation between the rows.

Why do coils need to be shaped? When should they be shaped?

The purpose of coil shaping is to make the shape and relevant dimensions of the coil meet the design requirements and make the end shape of the entire coil basically consistent. In order to reduce insulation damage, shaping is carried out after the inter-turn insulation wrapping and before the ground insulation wrapping.

What does inter-turn gelling mean? What is its function?

Inter-turn gelling refers to hot pressing the turns of wire in the straight part of the coil into a solid whole. Its function is to make the cross-sectional dimensions of the coil meet the requirements, provide a guarantee for the thickness of the main insulation, and improve the rigidity of the coil and reduce the deformation of the coil during the manufacturing process.

What are the basic requirements for insulating tape wrapping?

① Half-fold package is accurate.

②The layers are flat and without folds.

③The tension of the strap is appropriate.

④The bandaging direction is the same.

⑤The number of layers meets the requirements.

What are the two methods of insulating lead wires?

There are two ways to wrap lead insulation: one is to wrap the lead insulation first and then wrap the end insulation; the other is to wrap the lead insulation during the process of wrapping the end main insulation.

What is insulation overlap? What are the overlap methods?

Insulation overlap is when the slot insulation and end insulation of the ring-type stator coil are wrapped with two materials. The two materials should be overlapped at a certain position, which is called insulation overlap. It is divided into wrap insulation overlap and wrap insulation overlap.