What are the advantages of polyester insulated lead wire in terms of corona resistance and partial discharge resistance?
Publish Time: 2026-01-05
In fully hermetically sealed refrigeration compressor motors, the winding wires are subjected to harsh environments of high temperature, high pressure, high humidity, and the coexistence of refrigeration oil and refrigerant. Especially with the widespread use of variable frequency drives, the motor windings are subjected to high-frequency pulse voltages, which can easily trigger partial discharge at weak insulation points, leading to corona corrosion, rapid insulation deterioration and breakdown, and ultimately, inter-turn short circuits or motor failure. Polyester insulated lead wire, employing a double composite structure of polyester fiber braided layer and polyester film, exhibits significant advantages in corona resistance and partial discharge resistance due to its unique material properties and multi-layer barrier design, making it a key material for ensuring the long lifespan and high reliability of compressor motors.1. Dense Thin Film Layer: Constructing the First High Dielectric Strength BarrierThe core inner layer of the polyester insulated lead wire is a biaxially oriented polyester film, directly wrapping a flexible, round copper wire. This film has excellent dielectric properties, effectively blocking the development of electron avalanche in areas of concentrated electric field. More importantly, its smooth, non-porous surface avoids the micropores or pinholes in the enamel film of traditional enameled wires, which can become the starting point for partial discharge. At a working voltage of 600V, this film provides ample safety margin, significantly delaying the onset voltage threshold of partial discharge and suppressing discharge at its source.2. Braided Layer Buffer: Absorbing Electrical Stress and Suppressing Corona ErosionThe outer polyester fiber braided sheath not only improves mechanical abrasion resistance but also plays a crucial role in corona resistance. When a high-frequency pulse voltage is applied to the winding, the electric field distribution on the conductor surface is uneven, easily forming high-field-strength regions at sharp corners or air gaps. The braided layer, composed of countless interwoven fine fibers, contains micron-level voids that can partially "accommodate" ionized gas, reducing the local electric field strength. Simultaneously, its flexible structure absorbs fretting friction caused by electromagnetic vibrations, preventing the insulation layer from developing new microcracks due to repeated friction—cracks that are often the breeding ground for corona channels. Furthermore, polyester fibers themselves have a high corona resistance life, consuming some energy in the early stages of discharge and slowing down the damage process of the main insulation layer.3. Solvent-Free Structure: Eliminating Discharge Sources Caused by Air Gap and ImpuritiesUnlike traditional impregnated enameled wires, this polyester-insulated lead wire uses a dry composite process, eliminating the need for organic solvents or impregnation varnishes. This fundamentally avoids defects such as residual bubbles due to solvent evaporation and micropores formed by curing shrinkage, significantly reducing the number of internal air gaps. Air gaps are the primary sites of partial discharge—under an alternating electric field, the gas within the air gap is ionized, continuously bombarding the insulation material, causing "electrical trees" to grow. The polyester film and braided layer are tightly bonded, forming a low-porosity overall structure, effectively breaking the physical basis of the discharge chain reaction.4. Chemical Stability: Resisting Synergistic Aging in Refrigeration EnvironmentsInside a fully sealed compressor, the wires are constantly immersed in refrigeration oil and in contact with refrigerants such as R134a and R410A. Polyester materials have excellent chemical inertness to these media, resisting swelling, embrittlement, or the precipitation of low-molecular-weight substances, thus maintaining the integrity of the insulation structure. If the insulation develops micropores or interface peeling due to chemical corrosion, it will greatly exacerbate the risk of partial discharge. The stability of the polyester system ensures that the insulation layer remains dense even under high temperature and high pressure conditions, continuously resisting aging caused by electro-thermal-chemical multi-field coupling.5. Adaptable to Variable Frequency Applications: Addressing High-Frequency Stress ChallengesModern variable frequency compressors generally use PWM control, resulting in steep output voltage waveforms that easily generate voltage overshoot and standing wave effects at the winding ends, exacerbating partial discharge. Polyester insulated lead wire, with its high pulse voltage resistance and good thermal conductivity, can effectively disperse the heat generated by high-frequency losses, preventing hotspot accumulation and thermal-electric breakdown.Polyester insulated lead wire is not simply two layers of polyester material stacked together. Instead, it employs a four-in-one design philosophy of "dense thin film barrier + braided layer buffer dissipation + gapless structure + chemical stability," constructing multiple lines of defense against corona and partial discharge at the microscopic level. In the era of pursuing high-efficiency, long-life, and miniaturized fully sealed refrigeration compressors, this insulation solution, which combines electrical reliability and process adaptability, is becoming the preferred material for high-end motor windings, silently protecting the stable beating of the "heart" of every refrigerator and air conditioner.
