One of the most critical steps in the manufacturing of high-voltage motors is the production of coils. By chance, Ms. Can had the opportunity to visit a high-voltage motor manufacturing company. The company's advanced equipment and processes, with its high level of CNC and intelligent automation, inspired a strong sense of trust in the company.
However, some problems observed at the production site of the core component, the high-voltage coil, were unsatisfactory, especially in the crucial shuttle coil winding process. Numerous operational habits, such as sudden pulling, tugging, and jamming, damaged the insulation of the electromagnetic wire, which was quite alarming.
Today, Ms. [Name] will discuss the manufacturing process of high-voltage coils, drawing on issues she has personally witnessed. The basic manufacturing process for high-voltage coils is as follows: winding → inter-turn bonding → expansion → straight-side insulation wrapping → end insulation wrapping → inspection and testing.
Electromagnetic wire commonly used in high voltage motors
The most commonly used electromagnetic wires for high-voltage motors are SBEMB double-glass fiber-insulated film-wrapped flat copper wire and SBEFB self-adhesive double-glass fiber-insulated mica tape-wrapped copper flat wire. Different manufacturers will choose different heat resistance grades and insulation thicknesses due to differences in manufacturing processes and product characteristics. The storage and protection of electromagnetic wires are extremely important; any deficiency in the cleanliness, temperature, and humidity of the storage environment will inevitably lead to a significant reduction in the quality of the manufactured coils.
Fatal flaws in coil winding
●Irregular or even crisscrossed arrangement of the electromagnetic wires on the spools can cause sudden pulling and stopping during the winding process, resulting in displacement or damage to the insulation layer of the electromagnetic wires and a decrease in insulation performance.
● The magnet wire spool was damaged, causing some wire to pierce into the spool's gaps, severely damaging the magnet wire's insulation layer. Ms. Can witnessed this scene during her visit and the operator's indifference.
Coil winding instructions: During the winding process, strive for smoothness and uniform tension to ensure neat arrangement between turns, thereby ensuring the quality of subsequent curing meets requirements. Ms. Can observed that the site mainly used automatic winding machines. The problem of the electromagnetic wire being pulled and yanked too hard should not have occurred. However, the preparation of the spool was not meticulous enough, leaving a fatal hidden danger that was difficult to detect in subsequent processes.
Gelatinization process control
The gelation process is a crucial step. The gelation temperature should be appropriate to ensure that the adhesive can fully melt and penetrate, solidifying the coil into a single unit.
Practical problems encountered during the gelation process: 1) The enameled wire does not meet the requirements and cannot be gelled. 2) Problems with the storage and aging of the enameled wire lead to poor or unqualified gelation quality. 3) Inaccurate control of gelation temperature and time.
Expansion process control
This process is completed through the use of necessary molds and equipment. The key to this stage is the quality control of the coil ends. If the mold design or manufacturing is unreasonable, it can easily lead to severe deformation of the coil bending section under stress, resulting in localized damage to the electromagnetic wire insulation. The most direct consequence of this problem is inter-turn faults in the coil.
Insulation wrapping process
Insulation wrapping is the most tedious and difficult part of coil manufacturing. The number of wrapping layers varies depending on the rated voltage of the motor, and mica tape is used as the material. The most difficult part to control in this step is ensuring the conformity of the mica tape lamination.
The straight edges of the coil are generally wrapped by fully automated machines, which easily ensures a consistent overlap ratio. Some factories also use manual wrapping, which often results in inconsistent overlap ratios due to human error, with issues such as varying insulation thickness. If the insulation is too thick, the coil cannot fit into the slot; if the insulation is too thin, the withstand voltage will not meet requirements.
Tension control is crucial during coil wrapping, especially during the manual wrapping process at the coil ends. Loose wrapping can lead to air gaps between the insulation layers, posing a significant quality hazard.
During her visit, Ms. Can observed significant powder shedding from the mica tape used by the operators. This powder shedding is extremely serious during coil manufacturing, as mica is the main component of the mica tape responsible for high voltage and corona resistance. A reduction in the mica proportion directly results in substandard coils.
Another part of the insulation wrapping process is the wrapping of high and low resistance strips after the mica wrapping is completed. The purpose of the high and low resistance strips is to balance the electric field and prevent corona discharge. Low resistance strips are used on straight edges, and high resistance strips are used at the intersection of straight edges and ends. The high and low resistance strips must overlap without obstruction.
During her visit, Ms. Can observed that self-adhesive insulating tape was being used to separate high-resistance and low-resistance tapes. This involved first securing the low-resistance tape with the self-adhesive insulating tape and then wrapping the high-resistance tape. While this made the process more feasible, it significantly reduced the effectiveness of preventing dizziness.
