174 逆变器内部电感与母线件
逆变器内部的温度环境
逆变器外壳内的温度比想象中高。IGBT 模块散热片 80-100℃，电感磁芯 90-120℃，密闭机箱内部空气 70-90℃。
塑料件在这个温度里要工作 10-25 年。热老化是逆变器塑料件的头号失效机理，不是强度，不是阻燃。
长期工作温度怎么定
很多人看物性表的热变形温度（HDT）选料，这是错的。
HDT 是短时指标（0.45 MPa 载荷下变形 0.32 mm 的温度），长期工作温度一般只有 HDT 的 60-70%。
PA66-GF25 的 HDT 是 250℃，长期工作温度只有 120-140℃。
电感骨架工位 110℃，PA66 刚好够用；到 130℃ 就要升级 PA46 或高温尼龙。
现场还原：90℃ 舱温里的骨架
2025 年 1 月，合肥一家逆变器厂的散热实验室里，工程师给我们看一组对比件：两只电感骨架，同样的线圈，一只表面完好，一只已经变色发脆，骨架和铁芯之间出现了位移。
差别在哪：变色那只用的是普通 PA66-GF30，舱内实测热点温度 105℃，连续工作八个月后的样子。逆变器内部不是常温世界——功率器件周围热点 90-110℃ 是常态，电容区域、电感区域各有各的热区。
普通 PA66 在 105℃ 长期工作是超纲题：RTI 120℃ 看着够，但那是绝缘体系的老化指标，力学性能在 90℃ 以上衰减很快，玻纤增强牌也逃不掉。骨架变位后线圈和磁芯的耦合参数漂移，整机效率跟着掉。
换的方案：电感骨架用高温牌（PPA 或者改性 PA66 高耐热体系），按 RTI 140 起步、热变形温度 250℃ 以上选。成本每只贵几块钱，整机效率保住，返修率归零。
逆变器行业竞争白热化，单瓦成本压到极限，但热区材料这一块，省出来的每一块钱都在给返修率充值——这是我们在逆变器供应链里说得最多的一句话。
电感骨架的选材逻辑
电感骨架绕铜线，要耐绕线张力、耐浸漆烘烤、耐长期高温。
绕线张力会让骨架变形，所以要玻纤增强（GF25-GF30）。
浸漆后要 120-150℃ 烘烤，骨架在这个温度下不能变形。
PBT 的 HDT 只有 210℃，烘烤工位容易出问题，高要求电感骨架走 PA66-GF30 或 PA46。
母线支撑件要抗电动力
直流母线在短路瞬间承受巨大电动力，支撑件要高强度高刚性。
PA66-GF30 的强度 180 MPa 足够，但要注意高温下的强度衰减——90℃ 时只剩常温的 50%。
所以母线支撑件的安全系数要按高温强度算，不能按常温数据算。这是逆变器设计里最容易算错的一处。
深一层：电动力——母线支撑件的隐形考题
逆变器内部的母线排支撑件，很多选型只算了绝缘和耐温，漏了一条硬考题：短路电动力。
短路瞬间，母排之间流过几万安培的峰值电流，平行载流导体之间的电动力按电流平方放大——正常工作时的受力到短路瞬间可以放大上千倍。母排会在几毫秒内猛烈互斥，支撑件要在这一瞬间把母排按住。
这个力有多大：电流 20 kA、间距 5 cm 的母排，每米受力可以到几千牛，相当于一只手扛住一辆轿车的撞击——持续时间只有几毫秒，但件要在几百毫秒的短路保护动作窗口里扛住反复冲击。
塑料支撑件在这个场景里靠的是刚性和韧性同时在线：刚性不够，母排位移拉弧；韧性不够，冲击一次就裂。PA66-GF33 这类高刚高韧平衡的牌号是主流，部分大功率机型直接上金属支架加塑料绝缘衬。
设计验证走短路开断试验——整机通流测试一次，支撑件完好才算过。这一条在逆变器安规里是必测项，但很多方案公司的图纸在这一项上没有对材料提出量化要求，把宝押在「行业都这么做」上。
母线支撑件选料，问一句「短路试验用的什么牌号」，比十页物性表都有用。
CTI 和耐电痕化不能省
逆变器内部是 1000-1500 V 直流，直流电场下的电痕化比交流更严重。
母线支撑件、绝缘隔板的 CTI 要 ≥ 400 V，最好 600 V。
同时机箱内部湿度波动会产生凝露，湿热环境下的耐电痕化验证必须做——
IEC 60587 斜面法 3.5 kV 6 h 不击穿。
降本的边界在哪里
逆变器行业降本压力大，塑料件自然是目标。但有三处不能降：电感骨架（失效就是炸机）、母线支撑（短路时飞弧）、绝缘隔板（爬电起火）。
这三处的塑料件只占 BOM 的百分之几，降这点成本换来的是整机的售后风险。可以降的是外观件和防护件。
工程实测：4 条强制测试
测试1：长期工作温度。PA66-GF25 HDT 250℃ 但长期只有 120-140℃，PA46 长期 160-180℃——按长期温度选。
测试2：浸漆烘烤。150℃ 烘烤 2 h，PA66-GF30 无变形，PBT-GF30 轻微变形——高要求骨架走 PA66。
测试3：高温强度。PA66-GF30 在 90℃ 强度为常温的 50%——安全系数要按高温算。
测试4：斜面法耐电痕化。3.5 kV 6 h，高 CTI PA66 通过，普通阻燃 PA66 在 2.5 h 击穿。
追问三连：采购最常问的三件事
一问：热区件怎么划定界线。 按实测温度画热区图，别按经验猜：整机温升测试时布热电偶，90℃ 以上算热区，热区件按 RTI 高一档选料。热区图每年更新一次——功率密度年年涨，去年的图今年就不够用了。
二问：PPA 和改性 PA66 怎么选。 简单线：长期工作 120℃ 以上的部位直接 PPA（PA46/PA6T 类），别硬挺 PA66；110℃ 以下高耐热改性 PA66 够用且便宜。边界温度上多花几块钱的料费，比边界温度下赌返修率划算。
三问：CTI 和耐温哪个优先。 两个都是硬门槛，不存在优先，只有「都达标」和「不合格」两种状态。紧凑设计里爬电距离被压缩，CTI 要往 600 档取，这个档位的高耐热牌价格明显上浮——设计在最初画板的时候就要把爬电距离留够，给材料留活路。### 算一笔材料账：热区材料的效率账
逆变器热区材料还牵着一条容易被忽略的线：效率。把这条线讲清楚，材料的预算就从成本项变成了收益项。
电感骨架的耐温档不够时，工程上常见的补救是加大散热设计（更大风道、更厚导热垫），或者降额运行（同功率下限制输出）。两条路的代价都落在整机上：散热加大，成本和体积上浮；降额运行，每瓦收益直接缩水。
反过来，热区件换成高耐热牌，骨架在 105℃ 热点下尺寸稳定，磁芯耦合不漂，整机可以在更高的环温下满载运行——户外机柜夏天满载发电的时长，直接决定电站收益。
一个 100 kW 组串逆变器的案例口径：热区材料升级增加整机成本约 15 元，换来的是夏天正午少降额运行的两小时。按 25 度电折算，一年回本，之后全是赚的。
逆变器行业的竞争已经卷到「环境温度 45℃ 满载」成为卖点——这个卖点的背后是热区材料。销售页面上不会写 PPA 和 PA66 的区别，但每一台在正午满载跑的机器都在替材料投票。### 边界声明
| 工况 | 推荐材料 |
|---|
| 电感骨架 110℃ 以下 | PA66-GF30 |
| 电感骨架 130℃ 以上 | PA46-GF30 或高温尼龙 |
| 母线支撑 | PA66-GF30 高 CTI |
| 绝缘隔板 | 高 CTI PBT |
| 外观防护件 | 普通阻燃 PA66 |
工程备忘
逆变器内部件量产前必须做长期热老化 + 高温强度 + 斜面法耐电痕化三项。按长期工作温度选料，不要看 HDT。
实战案例：常见踩坑与正解
踩坑一：用常规 PA66 做户外逆变电感件，没加耐候体系，两年就粉化开裂。正解：光伏储能件的设计寿命是 25 年，必须走专用耐候牌号——UV 吸收剂 + HALS + 抗氧剂三件套缺一不可，并且要 3000 h 氙灯老化验证。踩坑二：只看常温强度不看湿热老化后的强度。逆变电感件装在户外，湿热老化 1000 h 后强度保持率低于 70% 的料不能用。正解：拿湿热老化后的数据选料，不拿常温数据选料。踩坑三：为了过认证临时换料，换完没重新做老化验证，批量装机后集中失效。正解：换料号必须重跑全套老化，这是光伏行业的基本规矩。
反向案例：降本矩阵里的一列红字
2024 年下半年，某逆变器厂做年度降本，材料降本矩阵里列了一项：电感骨架从 PPA 换成高耐热改性 PA66，单瓦降本 0.003 元，按年度出货量算是一笔可观的数字。
验证阶段出了分歧：常规老化测试通过，但 125℃ 长期老化（2000 小时）的对比数据显示，改性 PA66 的拉伸保持率是 68%，PPA 是 85%。按整机 15 年寿命折算，风险敞口在第六到八年。
工程团队把红字拍在降本会上：这一列不签。
最后走了一个折中方案：只把边缘冷区的小电感骨架换掉，热区大电感维持 PPA，降本目标完成七成，风险敞口压到可忽略。
这个案例好在它展示了「验证体系」的价值：没有那组 2000 小时数据，这项降本会以「测试通过」的名义上路，六年后市场返修率抬头的账，没人能追回到当年的降本矩阵上。
降本不是不能做，是要让数据来画红线——红线画在纸上的成本，永远比画在市场上的低。### 延伸判断：验证顺序不要搞反
逆变电感件的验证有固定顺序，跳过前面的直接做后面的，等于白做。
第一步验证材料本身：力学、热学、阻燃、电气这几项，确认料号没选错。
第二步验证工艺窗口：同一批料在不同模温、不同保压下打出来的件，性能差异可能超过 20%，工艺窗口要跑出来。
第三步才做整机或整件验证：装到实际工况里跑寿命。很多人的顺序是反的——直接装机跑寿命，不合格了不知道是料的问题还是工艺的问题，于是反复换料，半年出不了结果。
把这三件事写成一张表发给供应商，比打十通电话有用——逆变电感件的选型沟通成本，基本都花在这几项反复确认上。
最后一组问答：三个纠结时刻的裁决
纠结一：整机厂压价，热区料能不能让。 不能让，但可以拆：冷区件配合降，热区件单价不动、以量换价。热区料降档省的钱和返修的账前面算过，让价的谈判空间要从别的科目找——把热区划成「不可谈判项」写进报价逻辑，客户反而尊重。
纠结二：PPA 太贵，能不能用「高耐热 PA66」顶着干。 看热点温度：110℃ 以下勉强可议，120℃ 以上别顶——减半规律在那里等着，顶上去的每一年都在加速老化。材料的边界不靠意志力突破。
纠结三：短路试验做不做整机级。 做。母线支撑件的电动力验证没有缩水版，缩水版测的是「小电流下的完好」，而失效窗口在万安培——这一项省下的试验费，按失效后的整机索赔计，是试验费的一百倍起。### 补记：三个现场判断信号
信号一：热区骨架变色发脆。 热氧老化进行中，整批按热区图复核材料耐温档位，漏网的比报修的多。
信号二：母线支撑件位移或裂纹。 电动力验证没做扎实，立即复算短路工况，这类件的失效窗口在故障瞬间，赌不得。
信号三：整机效率缓慢下降。 排查磁件位置漂移——骨架蠕变或热变形导致耦合参数漂移，材料耐温档不够，先测热点温度再定方案。### 验证顺序：三步走完再下单
第一步，画热区：整机温升测试布点画图，90℃ 以上区域材料按 RTI 高一档配置。
第二步，验老化：热区件做 2000 小时高温老化，力学保持率按 80% 线取合格。
第三步，验电动力：母线支撑件按短路工况做开断试验，这一项没有替代方案。三步走完，逆变器的热区材料就有了设计级的保障。
结语
只做一件事——选料这件事，越早问越省事。
这类件的选料与试模，可以一起聊。
174 Inverter Internal Inductor and Busbar Components
The temperature environment inside the inverter
The temperature inside the inverter casing is higher than expected. The IGBT module heatsink is 80-100°C, the inductor core is 90-120°C, and the air inside the sealed enclosure is 70-90°C.
Plastic parts can operate at this temperature for 10-25 years. Thermal aging is the primary failure mechanism for inverter plastic parts—not strength, not flame retardancy.
How to determine the long-term working temperature
Many people choose materials based on the heat deflection temperature (HDT) listed in the property table, which is wrong.
HDT is a short-term indicator (the temperature at which deformation is 0.32 mm under a load of 0.45 MPa), and the long-term operating temperature is generally only 60-70% of the HDT.
The HDT of PA66-GF25 is 250°C, and the long-term operating temperature is only 120-140°C.
For the inductor frame workstation, 110°C is just enough for PA66; at 130°C, you need to upgrade to PA46 or high-temperature nylon.
On-site restoration: the skeleton in a 90℃ cabin
In January 2025, in the thermal testing laboratory of an inverter factory in Hefei, an engineer showed us a set of comparison parts: two inductor frames with the same coils, one with a perfect surface, and the other already discolored and brittle, with displacement between the frame and the core.
What's the difference: the one that changes color uses ordinary PA66-GF30. The actual measured hotspot temperature inside the cabin is 105°C, looking like this after eight months of continuous operation. The inside of an inverter is not a room-temperature environment — hotspots around power devices of 90-110°C are normal, and the capacitor area and inductor area each have their own thermal zones.
Ordinary PA66 operating long-term at 105°C is exceeding its limits: RTI of 120°C looks sufficient, but that is the aging indicator of the insulation system, and mechanical properties degrade rapidly above 90°C, even glass fiber reinforced grades cannot escape this. After the frame shifts, the coupling parameters of the coil and the magnetic core drift, and the overall machine efficiency drops accordingly.
Alternative solution: Use high-temperature grade (PPA or modified PA66 high heat-resistant system) for the inductor core. Choose based on RTI 140 as a starting point and a heat distortion temperature above 250°C. The cost per piece is a few yuan more, but it maintains the overall machine efficiency and reduces the repair rate to zero.
The competition in the inverter industry is heating up, and the cost per watt has been pushed to the limit, but in the area of thermal materials, every dollar saved is essentially adding to the repair rate—this is the sentence we say most often in the inverter supply chain.
Selection logic of inductor core materials
The inductor core is wound with copper wire, which must withstand winding tension, varnish impregnation and baking, and long-term high temperatures.
Winding tension can deform the framework, so it needs fiberglass reinforcement (GF25-GF30).
After dipping in paint, it needs to be baked at 120-150°C, and the frame must not deform at this temperature.
PBT's HDT is only 210°C, making the baking station prone to problems. High-demand inductor frames use PA66-GF30 or PA46.
Busbar supports must resist electrodynamic force
The DC busbar withstands enormous electrodynamic forces at the moment of a short circuit, so the supports must have high strength and high rigidity.
The strength of PA66-GF30, 180 MPa, is sufficient, but attention should be paid to the strength reduction at high temperatures — at 90℃ it is only 50% of that at room temperature.
Therefore, the safety factor of the busbar support should be calculated based on high-temperature strength, not on normal-temperature data. This is the most common calculation mistake in inverter design.
A Deeper Look: Electrodynamics—The Hidden Exam Questions of Busbar Supports
For the busbar supports inside the inverter, many selections only consider insulation and temperature resistance, overlooking a tough test question: short-circuit electrodynamic force.
At the moment of a short circuit, tens of thousands of amperes of peak current flow between the busbars, and the electromagnetic force between parallel current-carrying conductors is amplified according to the square of the current — the force that exists during normal operation can be magnified more than a thousand times at the instant of the short circuit. The busbars will strongly repel each other within a few milliseconds, and the supports have to hold the busbars in place at that moment.
How strong is this force: For a busbar with a current of 20 kA and a spacing of 5 cm, the force per meter can reach several thousand newtons, equivalent to the impact of a person holding up a car with one hand—lasting only a few milliseconds, but the component has to withstand repeated shocks within the short-circuit protection action window of a few hundred milliseconds.
Plastic supports in this scenario rely on both rigidity and toughness at the same time: if the rigidity is insufficient, the busbar will arc due to displacement; if the toughness is insufficient, it will crack after a single impact. Grades like PA66-GF33, which have a high-rigidity and high-toughness balance, are mainstream, and some high-power models directly use metal brackets with plastic insulation liners.
Design verification goes through the short-circuit interruption test — a full current test of the complete unit, and it is only considered passed if the support components remain intact. This item is a mandatory test in inverter safety standards, but many design companies' drawings do not specify quantitative requirements for the materials in this item, relying instead on the idea that 'the industry all does it this way.'
When selecting materials for busbar supports, asking 'What grade is used for the short-circuit test?' is more useful than ten pages of material property tables.
CTI and tracking resistance cannot be skipped
Inside the inverter is 1000-1500 V DC, and tracking under a DC electric field is more severe than under AC.
The CTI of busbar supports and insulating partitions should be ≥ 400 V, preferably 600 V.
At the same time, fluctuations in the humidity inside the chassis can cause condensation, and verification of resistance to electrical tracking in a hot and humid environment must be carried out—
IEC 60587 Inclined plane method 3.5 kV 6 h no breakdown.
Where are the boundaries of cost reduction?
The inverter industry faces significant cost reduction pressure, and plastic parts are naturally the target. However, there are three areas where costs cannot be cut: the inductor frame (failure could cause the device to explode), the busbar support (arc could fly during a short circuit), and the insulation barrier (creepage could lead to fire).
The plastic parts in these three locations only account for a few percent of the BOM. Reducing costs here would trade for the after-sales risk of the entire machine. What can be reduced are the appearance parts and protective parts.
Engineering Test: 4 Mandatory Tests
Test 1: Long-term working temperature. PA66-GF25 HDT 250℃ but long-term only 120-140℃, PA46 long-term 160-180℃ — choose according to long-term temperature.
Test 2: Varnish baking. Baked at 150°C for 2 hours, PA66-GF30 shows no deformation, PBT-GF30 shows slight deformation — high-demand frameworks should use PA66.
Test 3: High temperature strength. PA66-GF30 has 50% of its room temperature strength at 90°C — the safety factor should be calculated based on high temperature.
Test 4: Inclined plane method for tracking resistance. 3.5 kV for 6 hours, high CTI PA66 passed, ordinary flame-retardant PA66 broke down in 2.5 hours.
Three Consecutive Follow-up Questions: The Three Most Common Questions in Procurement
Question: How to define the boundaries of hot zone components. Draw a hot zone diagram based on measured temperatures, not based on experience or guesswork: during the overall temperature rise test of the machine, place thermocouples, and consider areas above 90°C as hot zones. Select materials for hot zone components one RTI level higher. Update the hot zone diagram annually—since power density increases every year, last year's diagram will not be sufficient for this year.
Second Question: How to choose between PPA and modified PA66. Simple guideline: For parts that work long-term above 120°C, go directly with PPA (PA46/PA6T type), don't stubbornly use PA66; for high-heat parts below 110°C, modified PA66 is sufficient and cheaper. Spending a few extra bucks on material for borderline temperatures is more cost-effective than gambling on repair rates at borderline temperatures.
Three questions: Which should take priority, CTI or heat resistance? Both are hard constraints, so there is no priority; there are only two states: 'both meet the standard' and 'non-compliant.' In compact designs, the creepage distance is compressed, and CTI needs to reach the 600 level. High heat-resistant brands at this level are significantly more expensive — during the initial design stage, the creepage distance needs to be reserved to give the material some flexibility. ### Calculating a material account: the efficiency account of materials in high-temperature areas
The hot zone materials of the inverter are also connected to a line that is easily overlooked: efficiency. Clarifying this line turns the material's budget from a cost item into a revenue item.
When the temperature rating of the inductor core is insufficient, a common engineering remedy is to enhance the cooling design (larger air channels, thicker thermal pads), or to operate at reduced capacity (limit output at the same power). Both approaches incur costs for the whole machine: enhanced cooling increases cost and size; reduced operation directly lowers efficiency per watt.
On the other hand, by replacing the hot zone components with high heat-resistant grades, the frame maintains dimensional stability at 105°C hot spots, the magnetic core coupling does not drift, and the entire machine can operate at full load under higher ambient temperatures—how long an outdoor cabinet can generate at full load in summer directly determines the power station's revenue.
Case estimate for a 100 kW string inverter: Upgrading the materials in the hot zone increases the total machine cost by about 15 yuan, in exchange for two hours of reduced derating at noon in the summer. Based on a power conversion rate of 25 yuan per unit, it pays back in a year, and everything after that is profit.
Competition in the inverter industry has escalated to making 'full load at an ambient temperature of 45℃' a selling point — behind this selling point are thermal zone materials. The sales pages won't mention the difference between PPA and PA66, but every machine running at full load at noon is voting for the materials. ### Boundary Statement
| Operating condition | Recommended materials |
|---|
| Inductor frame below 110℃ | PA66-GF30 |
| Inductor core over 130℃ | PA46-GF30 or high-temperature nylon |
| bus support | PA66-GF30 High CTI |
| Insulating baffle | High CTI PBT |
| Exterior protective parts | General flame-retardant PA66 |
Engineering Memo
Before mass production of inverter components, long-term thermal aging, high-temperature strength, and inclined plane tracking resistance must be carried out. Materials should be selected according to long-term operating temperature, not by looking at HDT.
Practical Case Study: Common Pitfalls and Correct Solutions
Pitfall 1: Using regular PA66 for outdoor inverter inductors without adding weather-resistant formulations, resulting in chalking and cracking within two years. Correct approach: The design lifespan of photovoltaic energy storage components is 25 years, so a dedicated weather-resistant grade must be used — the trio of UV absorbers, HALS, and antioxidants is essential, and 3000-hour xenon lamp aging tests must be conducted. Pitfall 2: Only considering room temperature strength and ignoring strength after damp heat aging. If an inverter inductor is installed outdoors, materials whose strength retention drops below 70% after 1000 hours of damp heat aging cannot be used. Correct approach: Select materials based on data after damp heat aging, not room temperature data. Pitfall 3: Temporarily changing materials to pass certification, but failing to redo aging tests after the change, resulting in collective failures after mass installation. Correct approach: Changing material grades must be followed by the full set of aging tests — this is the basic rule in the photovoltaic industry.
Reverse case: a column of red numbers in the cost reduction matrix
In the second half of 2024, a certain inverter manufacturer carried out the annual cost reduction. In the materials cost reduction matrix, one item was listed: changing the inductor frame from PPA to high-heat-resistant modified PA66, reducing the cost by 0.003 yuan per watt, which amounts to a considerable figure based on the annual shipment volume.
Disagreements arose during the verification phase: conventional aging tests passed, but the comparison data from long-term aging at 125℃ (2000 hours) showed that the tensile retention rate of modified PA66 was 68%, while PPA was 85%. Based on a 15-year lifespan of the whole machine, the risk exposure occurs in the sixth to eighth year.
The engineering team highlighted in red at the cost reduction meeting: This item will not be approved.
In the end, a compromise was reached: only the small inductor cores in the edge cold areas were replaced, while the large inductors in the hot areas maintained the PPA. The cost reduction target was achieved by 70%, and the risk exposure was reduced to a negligible level.
The good thing about this case is that it demonstrates the value of the 'verification system': without that set of 2000 hours of data, this cost reduction would have gone live under the name of 'passing tests,' and six years later, when market repair rates rise, no one would be able to trace the account back to the cost reduction matrix of that year.
Cost reduction is not impossible; it's about letting data draw the red line—the cost of drawing the red line on paper is always lower than drawing it in the market. ### Extended judgment: Don't reverse the verification sequence
The verification of inverter inductive components follows a fixed sequence; skipping the earlier steps and directly doing the later ones is equivalent to doing nothing.
Step one is to verify the material itself: mechanics, thermology, flame retardancy, and electrical properties, making sure the part number was not chosen incorrectly.
Step 2: Verify the process window: Parts produced from the same batch of material under different mold temperatures and holding pressures may have performance differences exceeding 20%, so the process window needs to be established.
The third step is to carry out full machine or complete component verification: install it in actual working conditions and run a lifespan test. Many people do it in the opposite order—they directly install the machine to run the lifespan test, and if it fails, they don’t know whether it’s a material issue or a process issue, so they keep changing materials repeatedly and can’t get results for half a year.
Write these three things into a table and send it to the supplier; it’s more useful than making ten phone calls—the communication cost for selecting inverter inductors is basically spent on repeatedly confirming these few items.
The final Q&A: The verdict on three moments of dilemma
Dilemma 1: The complete machine manufacturer is pressing for a price reduction. Can we compromise on hot-zone materials? We can't compromise, but we can split: lower the price on cold-zone parts, keep the unit price of hot-zone parts unchanged, and trade volume for price. The savings from downgrading hot-zone materials and the cost of repairs have been calculated, so the negotiation room for giving a discount should come from other items—by classifying the hot-zone as a 'non-negotiable item' in the quotation logic, the customer will actually respect it.
Dilemma Two: PPA is too expensive, can we just use 'high heat-resistant PA66' instead? Looking at the hotspot temperature: below 110℃ it’s barely acceptable, above 120℃ don’t push it—the halving rule is waiting there, every year you push it accelerates aging. The material's limits cannot be overcome by willpower.
Issue Three: Should the short-circuit test be performed at the full machine level? Yes. The electrodynamic verification of the busbar supports has no scaled-down version; the scaled-down version only tests 'integrity under small current,' while the failure window is in the tens of thousands of amperes — the cost of skipping this test, in terms of claims after failure at the full machine level, is at least a hundred times the test cost. ### Supplementary Note: Three on-site judgment signals
Signal 1: The hot zone frame changes color and becomes brittle. Thermal-oxygen aging is in progress. Check the material's temperature rating for the entire batch according to the hot zone map; more items are missed than reported for repair.
Signal 2: Displacement or cracks in bus support components. Electrodynamic verification was not done thoroughly. Recalculate the short-circuit conditions immediately. The failure window for this type of component is at the instant of fault and cannot be risked.
Signal Three: The overall machine efficiency is slowly declining. Check for shifts in the position of magnetic components — creep or thermal deformation of the frame causing drift in coupling parameters, materials not rated for sufficient temperature; measure the hotspot temperature first before determining a plan. ### Verification sequence: complete the three steps before placing an order
Step one, draw the hot zone: Create a layout of the temperature rise test points for the whole machine, and for areas above 90°C, configure materials according to one level higher than the RTI.
Step two, aging test: The hot zone components undergo 2000 hours of high-temperature aging, and the mechanical retention rate is qualified if it meets the 80% line.
Step three, check electrical power: The busbar support is subjected to an opening test under short-circuit conditions, and there is no alternative for this. After completing the three steps, the inverter's thermal zone materials have design-level assurance.
Conclusion
Just do one thing—choosing materials—and the earlier you ask, the less trouble it will be.
The material selection and mold trial for this type of part can be discussed together.
