驱动电机绝缘件用什么改性尼龙?耐温等级排在力学前面

应用领域 发布时间: 2026-09-16 3264 阅读

155 What type of modified nylon is used for drive motor insulation?

Types of motor insulation components

Modified nylon insulation components in drive motors include: winding insulation skeleton (the skeleton of skeleton windings), slot insulation and slot wedges, end insulating parts, lead wire sheath and terminal block, and rotor rings.

Common requirements: temperature resistance rating (usually 155°C or 180°C), insulation strength, resistance to insulating varnish and lubricants, dimensional accuracy, and long-term thermal aging stability.

The primary indicator here is the temperature resistance grade, not mechanical properties.

On-site reconstruction: Comparative test at the edge of a paint immersion tank

In July two years ago, a new platform for a motor factory soaked standard test pieces from three suppliers directly into the production line's paint immersion tank. This practice is uncommon in the materials industry—most models use standard paint samples for testing, and they use paint from the production line, with concentration, temperature, and impurity levels all showing the real state.

After seven days, the samples from the three companies showed a clear gap: two showed no surface changes, while one showed fine cracks.

The technician at the crack company was initially unconvinced and retested the standard paint sample, finding the data good. The process engineer at the motor factory sent photos of the paint immersion tank over with a caption: Your paint is clean, our paint contains organic solvent residues and metal shavings, and the material must survive in our environment for fifteen years.

This phrase later became their fixed choice — laboratory conditions verify the intrinsic performance of materials, production line conditions verify material adaptability, both sets of data are indispensable.

The final winning grade remained stable in three categories: insulating paint immersion, 155-degree thermal aging, and thermal shock. After designation, it served for three years, with the motor insulation failure rate remaining below 0.03%. The photo of that tank edge test was even posted by the motor factory on the laboratory wall, with the title just four words: 'On-site is king.'

How to understand temperature resistance ratings ?

The temperature resistance rating of insulation materials (such as Class F 155°C, Class H 180°C) is not short-term resistance but long-term service life—

must meet a service life of over 20,000 hours at this temperature. PA66's actual long-term temperature resistance is 120-140°C, so ordinary PA66 can only be used for Class B or Class F insulation.

To make Class H (180°C), PPA or PPS is usually used. This is the first step in selecting motor insulation materials.

Resistant to insulating paint and oil

Motor windings need to be impregnated with insulating varnish (polyester or epoxy), and plastic parts must withstand solvents and high-temperature baking (usually baked at 150°C for several hours after impregnation).

At the same time, bearing lubricants and gear oil also come into contact with insulating parts. Therefore, insulating parts must be resistant to insulating paint, oil, and baking at 150°C.

Verification requires a combined test of varnish dipping + baking + thermal aging—this is the standard process for motor components.

Dimensional accuracy and assembly

Dimensional accuracy of insulating skeleton and slot wedges directly affects winding quality and assembly. The moisture absorption and expansion of PA is a risk here (2.5% moisture absorption, 0.6 % expansion).

There is an additional issue in motors: dimensional changes during paint dipping and baking—

High-temperature baking causes further crystallization of PA, changing size by 0.1%-0.3%.

Therefore, key dimensions should be measured after varnish immersion baking, not after forming.

Insulation strength and arc resistance

The dielectric strength of insulating components is usually required to be > 20 kV/mm, and arc resistance to > 120 s.

PA Good insulation performance in dry conditions but decreases after moisture absorption—this is a point to note in motor insulation.

Additionally, partial discharge (PD) inside the motor is the failure mechanism of high-voltage motors—motors on 800V platforms must focus on partial discharge resistance, which is a new technical requirement.

Deeper layer: What is behind the letters of temperature resistance grade ?

The temperature resistance ratings of motor insulation materials are indicated by letters: Class A 105°C, Class E 120°C, Class B 130°C, Class F 155°C, Class H 180°C.

This grade is not the maximum temperature the material can withstand; it is the rated value for a lifespan of 20,000 hours at that temperature. Understanding this makes the material selection approach correct—grade is a link between temperature and lifespan; looking at temperature alone is meaningless.

Modified nylon is positioned in motor insulation components at auxiliary insulation positions between Class B and F, such as slot wedges, gaskets, and terminal boards. The main insulation position is still handled by specialized insulating materials such as mica and polyimide film, while plastic parts serve to bear, isolate, and fix.

Recognizing this positioning means there will be no demand for plastic parts to do mica work, nor will plastic parts be bought at the main insulation price.

Insulating paint resistance is an unavoidable test. In the impregnation process, the paint solution contains active thinner and curing accelerator. Before curing, the paint has the strongest swelling attack on the plastic. For processes exposed for long periods at the dipping temperature, material verification must be conducted at the worst exposure time. For parts like junction boards that are assembled first and then impregnated, the validation conditions are a level harsher than slot wedges.

Extended judgment: Hidden variables of motor insulation components

There are three most easily missed hidden variables. First is moisture—if PA absorbs moisture before coating, high-temperature baking will cause the insulation paint to bubble and reduce insulation performance; after molding, it should be dried and stored.

Second, catalytic aging of copper ions—PA in contact with copper accelerates thermal oxidation aging (copper damage), so copper inhibitors should be used.

Third is wear under vibration—windings will slight under electromagnetic force, and insulation wear can lead to inter-turn short circuits.

Engineering Testing: 4 mandatory tests

Test 1: Long-term temperature resistance. PA66 long-term 120-140°C (Class F), PPA 180°C (Class H) — determine the temperature resistance grade before selecting materials.

Test 2: Dimensions after 150°C lacquer baking. Crystallization changes cause dimensional change of 0.2%—key dimensions must be measured after baking.

Test 3: Dielectric strength. Dry state 25 kV/mm, after moisture absorption it drops to 15 kV/mm—moisture control of the motor component.

Test 4: Copper damage aging at 150°C for 1000 hours. Copper inhibitor system tensile rate maintains 85%, without copper suppression reduced to 45%.

Boundary Declaration

Working ConditionsRecommended Materials Grade
F (155°C) Insulation ComponentsHeat-Resistant PA66 + Copper Inhibitor Grade
H (180°C) Insulation PartsPPA or PPS
Insulating Resistant Paint PartsImmersion paint + baking combination verification
Precision dimensioning partsPost-baking measurement + reserved variation
800V High-voltage motorFocus on partial discharge resistance

Engineering memo

Motor insulation The first indicator is temperature resistance rating (not mechanical properties)—PA66 can only be made as F grade; H grade requires PPA or PPS. Key dimensions should be measured after varnish immersion and baking, as high-temperature baking causes PA size to change by 0.2%.

Practical Case: Common pitfalls and correct answers

Pitfall 1: Choosing materials based on traditional automotive thinking ignores electrical safety requirements. Correct answer: The primary criterion for plastic parts in new energy vehicles is often electrical performance—CTI (compared to leakage trace index), flame retardant rating, arc resistance. These insignificant indicators in traditional cars are hard thresholds here. Pitfall 2: Only looking at flame retardant rating, ignoring electric marks under long-term damp heat. Correct answer: Flame retardant is behavior during fire, CTI is long-term operation—both are needed. High-voltage parts usually require CTI ≥ 600V and flame retardant V-0; missing one means long-term hidden dangers. Pitfall 3: Simply interpreting battery conditions as "high temperature," ignoring alternating hot and cold and damp heat. Correct answer: The battery pack is a composite environment of temperature alternating + humidity changes + coolant. Verify that a combination test of temperature shock + damp heat + coolant compatibility should be conducted. These three pitfalls are all checklists that must be checked before mass production.

Follow-up Triple Question: Three high-frequency questions readers have about motor insulation components

First question: What is the CTI of the insulating parts? Depends on the motor's operating voltage and pollution level. For low-voltage motors, the 400V CTI range is generally sufficient. For inverter power supply motors, due to voltage spikes, it is recommended to choose the 600V range. The widespread adoption of frequency converters has made this a standard item from a plus.

Second question: How much force does the slot wedge need to bear? The impact force during wire insertion and the electromagnetic force during operation are two sources of load. The impact of the wire insertion process is a short-term assessment, while electromagnetic vibration is a long-term assessment. Both the impact strength and fatigue resistance of the slot wedge material are required. During verification, simulate the wire embedding action for impact tests, then add vibration durability.

Third question: Does the moisture absorption of insulating components affect the motor? Yes. After moisture absorption by nylon insulating parts, the insulation resistance decreases. The standards for wet and tropical motors require insulation resistance to be wet. Choose a grade with low water absorption or use moisture-proof packaging. Both methods are feasible, so choose according to cost.

Reverse Case: A batch of terminal boards that have been stalled during the southern rainy season

A Motor Factory's low-cost motor uses ordinary PA66 circuit boards. The northern market has been fine for two years, but during the southern rainy season, insulation resistance warnings appear in bulk, and rework and replacement cost a quarter's profit. The material price difference for terminal boards is less than two yuan per piece, and replacement costs are a hundred times higher. The material list for motors in the humid and tropical regions is always a separate table.

Supplement: Another practical question from three readers

Fourth Question: How should the arc resistance requirements for insulating components be understood? Arc resistance refers to the material's ability to withstand arcs without conductivity. For components like terminal boards close to live parts, this indicator should be considered. Arc resistance and CTI are two different dimensions: one is tube arc ablation, the other is leakage and marking, both need to be considered.

Question 5: How much does the injection molding accuracy of electrical components affect motor performance? Thicker slot wedges can damage enameled wire, and shim thickness deviations affect air gap uniformity. Although the dimensional tolerances of insulating parts appear loose, in reality, every wire is connected to the motor's efficiency and quality stability. Precision injection molding here is not a bonus but a bottom line.

Question 6: What is the focus of motor factories' audits on insulating parts suppliers? Cleanliness and traceability. Surface dust from insulating parts can be introduced into windings during wire insertion; clean production control records are mandatory items for audits; Traceability requires that each batch can have traceable formula and process versions, and whether change management is standardized directly determines the audit results.

On-site observation

Observation 1: Incoming material inspections at motor factories are becoming more detailed. One motor factory expanded incoming insulation inspection from appearance dimensions to dielectric loss testing. A batch with high dielectric loss was stopped, only to be found to have its additive system updated in later years. The depth of inspection items reflects the losses the factory has suffered.

Observation 2: The widespread adoption of variable frequency motors is rewriting insulating component specifications. High-frequency spike voltages output by frequency converters cause higher stress on the first turn of windings, indirectly raising the electrical requirements for insulating components. Verification of new materials at designated locations under variable frequency operating conditions has become the new normal in recent years.

A set of numbers at the end

Number One: Regarding the usage per vehicle of insulating components. A single motor has more than ten types of insulation components from slots to terminals, and hybrid dual motors can directly double the price. The price per unit in this category is not high, but the total quantity is considerable, making it a typical long-tail treasure trove in motor matching.

Number Two, regarding the conversion of lifespan indicators. The motor's design life starts at 20,000 hours, and the insulation component's temperature rating life curve should be covered with a 30% margin. When suppliers provide life data, they clarify the evaluation criteria; 20,000 hours under different conditions are not the same concept.

Number Three, regarding cleanliness grades. Insulating component cleanliness acceptance is generally based on particle count; the mainstream industry standard is that visible particles per square decimeter do not exceed single digits. Clean production investment is one-time, and the risk of returns is ongoing, so this account is not hard to calculate.

Last Sentence

Ultimately, the selection of materials for motor insulation parts follows the motor's operating schedule. The more honestly the data is written, the more accurate the material selection. Fill in the three variables—temperature, paint immersion, and humidity—into the table, and leave the rest to data and verification.

Postscript

Readers new to insulating parts often ask: These parts look inconspicuous, so why are the fixed-point intervals so long? The answer lies in the hidden nature of failure—minor defects in insulating parts only become apparent after the motor ages for several thousand hours. The length of the verification cycle is the time it takes for failures to appear, so you can't skip them.

Conclusion

Before Pouring Materials into the Machine — The earlier you ask about material selection, the easier it is.

For material selection and mold trials for these types of pieces, you can chat together

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