Stator Vacuum Pressure Paint Impregnating Process

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Abstract: On the basis of composite insulation technology, the manufacturing technology of high voltage motor stator coil is improved, and a new manufacturing technology of motor stator coil, vacuum pressure impregnation painting technology, is put forward. This method has the advantages of less space occupation, better environment, less waste of material hours, high efficiency, and reliable quality.

Key words: High voltage motor; Stator coils; Vacuum pressure
In recent years, the application of high-voltage motor is increasing. The commonly used high-voltage motors are 3 KV, 6 KV and 10 KV.Because of the high voltage, it brings many difficulties to the manufacture of motor, especially the manufacture of stator coil.The stator coils are mostly manufactured by composite insulation process or semi-curable insulation process. The composite insulation process USES polyglue epoxy powder mica tape to wrap the linear part and mold to form. The ends are wrapped by lacquered cloth tape and then soaked with glue.Semi-curing insulation technology, the straight line and the end are wrapped with two kinds of multi-glue epoxy mica tape with different gelatinizing time respectively, the straight line insulation part is molded one by one by pressing mold, the end insulation is not impregnated with glue..The above two processes, which take up a lot of space, are difficult to insert wires, high repair rate, low efficiency, serious waste of materials and working hours, can be produced in single or small batches. If the mass production is not suitable, the following analysis will be made on a new manufacturing process of motor stator coils — vacuum pressure impregnation painting process.

1. Structure of stator coil
The high-voltage motor stator coil has two coil sides, which are embedded into two stator slots respectively when wired (3), as shown in FIG. 1.The distance between the two coil edges is called the pitch and is indicated by the number of slots crossed.FIG. 1(a) is a 6-pitch coil, and FIG. 1(b) is a 9-pitch coil.

2. Vacuum pressure paint impregnating process
Vacuum pressure paint impregnating process is the foundation of composite insulation process and semi-curing insulation process.The process flow is as follows:
Winding wire. One package of protective tape and one lead head treatment one form, one shape, one shape, one turn, one turn gelatinize, one turn test – one package of insulation for lead and one package of insulation against ground, one inspection test for corona layer, one insert wire – one vacuum pressure impregnation paint – one curing.The two most critical steps in the process are interturn gelatinization and vacuum pressure impregnation.

2.1 Vacuum pressure immersion paint.
Vacuum pressure impregnation is a rubble-less epoxy mica coated coil with interturn gelatinization directly embedded into the stator core. After passing the inspection, it is put into the oven to remove moisture, and then into the impregnation pot to pump vacuum pressure impregnation [5].Impregnant type solventless epoxy paint are available, and is a kind of commonly used for immersion under temperature low viscosity epoxy resin, viscosity of 50 ~ 80 cp, styrene as diluent, commonly used in the process of use and storage of viscosity increases gradually, for moderate viscosity change trend, must under the condition of dry air of low temperature storage, temperature control at around 40 c [6], the paint don’t within the prescribed temperature, in use process, can adjust viscosity with the method of adding a new paint.

2.2.1 Vacuum pressure paint impregnating equipment
Gh-vpi-2220 vacuum pressure paint impregnating equipment is mainly composed of impregnating tank, storage tank vacuum system, air pressure system, refrigeration system, control system, pipes, valves and so on.The impregnation ping tank is vertical, with a diameter of 2.2m and a depth of 2m, and bears a pressure of 0.7mpa.The vacuum system is composed of slide valve vacuum pump and Roots pump, etc. The vacuum degree is high. In order to help remove volatiles and moisture in the insulation, the absolute pressure should be less than 133Pa.The working pressure of the pressurization system is controlled at 0.3~0.7MPa and equipped with filters and air dryers.The refrigerating system can rapidly cool the paint after impregnation and maintain the low temperature required for the storage.

2.2.2 Technological parameters of vacuum pressure impregnation
The technological parameters of vacuum pressure impregnation lacquer are related to the insulation level of the motor. The technological parameters of F-grade vacuum pressure impregnation lacquer refer to Table 1.
Table 1 Technological parameter reference value of F grade vacuum pressure impregnation paint

No	Process	Temperature /℃	Vacuum residual pressure /Pa	Pressure /Mpa	Time /h	Remark
1	Pre-baking	95~110			6	In curing oven
2	Vacuuming in tank	50~60	≦40		2	In pressure impregnation tank
3	Paint	Room temperature			0.5
4	Pressurized			0.7	3
5	Return paint				0.25~4
6	Push into curing oven	180+/-5			≥8
7	Put out oven

3. Conclusion
Vacuum pressure impregnation paint process has the advantages of simple coil manufacturing, easy wire insertion, small insulation mechanical damage, good fixation, high insulation tightness and high thermal conductivity. After small batch trial, it occupies less space, good environment, less waste of material hours, high efficiency and reliable quality. It is the preferred process for batch manufacturing of high-voltage motor stator coils.

Editor: Frank Lee
Copyright: SIMUWU vacuum furnace